158 results on '"Rick A. Adams"'
Search Results
52. Integrating Ontogeny of Echolocation and Locomotion Gives Unique Insights into the Origin of Bats
- Author
-
Rick A. Adams and Richard T. Carter
- Subjects
0106 biological sciences ,0301 basic medicine ,Ontogeny ,Zoology ,Human echolocation ,Biology ,Sound production ,Evolutionary transitions ,010603 evolutionary biology ,01 natural sciences ,03 medical and health sciences ,030104 developmental biology ,Extant taxon ,Evolutionary biology ,Evolutionary developmental biology ,Ecology, Evolution, Behavior and Systematics - Abstract
The evolutionary sequence of events that led to flight and echolocation in bats is a compelling question in biology. Fundamentally lacking from this discussion is the ontogeny of how these two systems become functionally integrated producing an evolutionary developmental model. We build such a model by integrating growth and development of the cochlea, larynx, and sound production with the ontogeny of locomotion in newborn bats. In addition, we use available fossil and molecular data along with patterns of high frequency vocalization in extant mammals to model probable evolutionary transitions in bats. We find clear evidence that the ability to hear high frequency echolocation-like sounds preceded the ability to produce it and that a simple echolocation system was likely inherited from a shrew-like ancestor and was not an in situ evolutionary innovation of bats. Refinement of this system coevolved with sustained flight, both ontogenetically and evolutionarily, leading to the sophisticated echolocation observed today.
- Published
- 2016
53. S153. IMPAIRED THETA PHASE-COUPLING BETWEEN HIPPOCAMPUS AND MEDIAL PREFRONTAL CORTEX IN SCHIZOPHRENIA
- Author
-
Neil Burgess, Raphael Kaplan, Fanfan Zheng, Rick A. Adams, Oliver D. Howes, Sofie S. Meyer, Stelios Orfanos, Tiago Reis Marques, and Daniel Bush
- Subjects
Poster Session I ,business.industry ,AcademicSubjects/MED00810 ,Hippocampus ,medicine.disease ,behavioral disciplines and activities ,Psychiatry and Mental health ,Phase coupling ,Schizophrenia ,Medicine ,Prefrontal cortex ,business ,Neuroscience ,psychological phenomena and processes - Abstract
Background A genetic schizophrenia (Scz) mouse model has impaired hippocampal-prefrontal synchrony during spatial working memory (Sigurdsson et al., 2000, Nature). These Df(16)A(+/-) mice (models of the human 22q11.2 microdeletion) have impaired mPFC phase coupling to hippocampal theta (1–8 Hz) oscillations, which predicts performance. This deficit has never been demonstrated in human Scz subjects, however, and its mechanistic basis is unclear. Methods 18 Scz (8 unmedicated) and 26 age, gender and IQ-matched controls performed a spatial memory task whilst undergoing magnetoencephalography (MEG), and a ‘memory integration’ task dependent on hippocampal function (without MEG). A partly overlapping group of 33 Scz and 29 controls underwent positron emission tomography (PET) to measure the availability of GABAARs expressing the α5 subunit (concentrated on hippocampal somatostatin interneurons). Results We demonstrate – in the spatial memory task, during memory recall – that theta power increases in left medial temporal lobe (mTL) are impaired in Scz, as is theta phase coupling between mPFC and mTL. Importantly, the latter cannot be explained by theta power changes, head movement, antipsychotics, cannabis use, or IQ, and is not found in other frequency bands. Moreover, mPFC-mTL theta coupling correlated strongly with performance in controls, but not in Scz, who were mildly impaired at the spatial memory task and no better than chance on the memory integration task. Use of antipsychotic medication may ameliorate this mPFC-HC theta coupling deficit. Finally, mTL regions showing reduced theta phase coupling in Scz MEG participants overlapped substantially with areas of diminished α5-GABAAR availability in the wider Scz PET sample. Discussion These results indicate that impaired theta phase coupling between hippocampus and mPFC could underlie hippocampal-prefrontal dysconnectivity in schizophrenia, and impairments in the cognitive domains that depend on communication between these areas. They also imply α5-GABAARs (and the cells that express them) have a role in the phase coupling process.
- Published
- 2020
54. O6.5. JUMPING TO CONCLUSIONS ABOUT DECISION NOISE? A COMPUTATIONAL ANALYSIS OF THE RELATIONSHIP BETWEEN BELIEF UPDATING AND PSYCHOTIC SYMPTOMS IN A LARGE UK BIRTH COHORT
- Author
-
Jazz Croft, Anthony S. David, Rick A. Adams, Jon Heron, Stanley Zammit, Christoph Teufel, David Edmund Johannes Linden, and Paul C. Fletcher
- Subjects
Psychiatry and Mental health ,Noise ,medicine.medical_specialty ,Oral Session: Digital Health/Methods ,O6. Oral Sessions: Cognitive/ Other ,AcademicSubjects/MED00810 ,Jumping to conclusions ,medicine ,Computational analysis ,Audiology ,Birth cohort ,Psychology - Abstract
Background A number of studies show that people with psychotic disorders have abnormal belief-updating processes. In a commonly-used decision-making task, the beads task, participants infer which of two jars, each with a different ratio of coloured beads, a presented bead is drawn from, with an option to request further beads before reaching a decision. Previous studies suggest that people with psychotic symptoms request fewer beads (draws to decision; DTD) indicative of a ‘Jumping to conclusion’ (JTC) bias. In a modified version of this task, participants estimate the probability that beads have been drawn from one of the two jars on a sliding scale over a sequence of beads and are also told that the jar the beads are drawn from may switch. In this task, people with psychotic symptoms revise their estimations disproportionately in response to a change in colour of beads in a sequence (overadjustment bias). It is not clear what specific belief-updating processes drive these biases, how they arise, or if their association with psychotic symptoms is independent of confounding. We examined whether abnormal belief-updating processes are associated with psychotic experiences in a large, population-based sample, and whether they mediate the association between trauma and psychotic symptoms. Methods We used data from the Avon Longitudinal Study of Parents and Children birth cohort (n=2,879). Past-year frequent or distressing psychotic experiences (PEs) were assessed using the semi-structured PLIKS interview at age 24. Performance on the DTD and probability estimation tasks at age 24 were assessed using behavioural indices and computational modelling parameters (using ‘costed Bayesian’ and Hidden Markov Models respectively). Logistic regression was used to examine the association between belief-updating parameters (DTD task: cost of sampling, decision noise; Probability estimation task: adjustment rate, inference length, decision confidence, prior expectation of reversal, decision noise) and PEs. Estimates were adjusted for confounders (genetic risk for schizophrenia, socio-economic status, cognitive function). Mediation analysis tested abnormal belief-updating processes as a mediator between exposure to trauma (assessed ages 0–17 years) and age-24 PEs. Results In the DTD task, increased decision noise was associated with PEs (adjusted OR=1.89, 95% CI: 1.14, 3.13, p=0.014). There was little evidence of an association between the JTC bias and PEs (OR= 1.13; 95% CI: 0.45, 2.82). For the probability estimation task, there was an association between a higher prior expectation that the jars that will switch during the sequence (expectation of reversal) and PEs (adjusted OR = 2.28; 95% CI 1.39, 3.74, p=0.001). Our findings were minimally attenuated by confounding ( Discussion Our results suggest that abnormal belief-updating processes (increased decision noise; greater prior expectation of reversal) are associated with PEs, and that this is not explained by general cognitive ability, shared genetic risk, or social background. Previous observations of association between the JTC bias and psychosis may be due to sub-optimal performance rather than a bias for making a decision on less evidence. The results also suggest that an increased expectation of change is associated with the early stages of psychosis symptom development. Our mediation result does not support the hypothesis that the belief-updating processes examined here lie on the causal pathway between trauma exposure and PEs.
- Published
- 2020
55. Attractor-like Dynamics in Belief Updating in Schizophrenia
- Author
-
Rick A. Adams, Jonathan P. Roiser, Christoph Mathys, James Gilleen, Gary Napier, University of Zurich, and Adams, Rick A
- Subjects
0301 basic medicine ,Psychosis ,Schizophrenia (object-oriented programming) ,Bayesian probability ,610 Medicine & health ,Bayesian inference ,Bayesian ,170 Ethics ,03 medical and health sciences ,beads task ,0302 clinical medicine ,attractor model ,Attractor ,medicine ,10237 Institute of Biomedical Engineering ,psychosis ,Attractor network ,disconfirmatory bias ,schizophrenia ,General Neuroscience ,2800 General Neuroscience ,medicine.disease ,030104 developmental biology ,Settore M-PSI/02 - Psicobiologia e Psicologia Fisiologica ,Dynamics (music) ,Psychology ,030217 neurology & neurosurgery ,Diagnosis of schizophrenia ,Cognitive psychology - Abstract
Subjects with a diagnosis of schizophrenia (Scz) overweight unexpected evidence in probabilistic inference: such evidence becomes “aberrantly salient.” A neurobiological explanation for this effect is that diminished synaptic gain (e.g., hypofunction of cortical NMDARs) in Scz destabilizes quasi-stable neuronal network states (or “attractors”). This attractor instability account predicts that (1) Scz would overweight unexpected evidence but underweight consistent evidence, (2) belief updating would be more vulnerable to stochastic fluctuations in neural activity, and (3) these effects would correlate. Hierarchical Bayesian belief updating models were tested in two independent datasets (n= 80 male andn= 167 female) comprising human subjects with Scz, and both clinical and nonclinical controls (some tested when unwell and on recovery) performing the “probability estimates” version of the beads task (a probabilistic inference task). Models with a standard learning rate, or including a parameter increasing updating to “disconfirmatory evidence,” or a parameter encoding belief instability were formally compared. The “belief instability” model (based on the principles of attractor dynamics) had most evidence in all groups in both datasets. Two of four parameters differed between Scz and nonclinical controls in each dataset: belief instability and response stochasticity. These parameters correlated in both datasets. Furthermore, the clinical controls showed similar parameter distributions to Scz when unwell, but were no different from controls once recovered. These findings are consistent with the hypothesis that attractor network instability contributes to belief updating abnormalities in Scz, and suggest that similar changes may exist during acute illness in other psychiatric conditions.SIGNIFICANCE STATEMENTSubjects with a diagnosis of schizophrenia (Scz) make large adjustments to their beliefs following unexpected evidence, but also smaller adjustments than controls following consistent evidence. This has previously been construed as a bias toward “disconfirmatory” information, but a more mechanistic explanation may be that in Scz, neural firing patterns (“attractor states”) are less stable and hence easily altered in response to both new evidence and stochastic neural firing. We model belief updating in Scz and controls in two independent datasets using a hierarchical Bayesian model, and show that all subjects are best fit by a model containing a belief instability parameter. Both this and a response stochasticity parameter are consistently altered in Scz, as the unstable attractor hypothesis predicts.
- Published
- 2018
56. Sonar Surveys for Bat Species Richness and Activity in the Southern Kalahari Desert, Kgalagadi Transfrontier Park, South Africa
- Author
-
Gary Kwiecinski and Rick A. Adams
- Subjects
0106 biological sciences ,Kgalagadi Transfrontier Park ,Rhinolophus fumigatus ,bats ,Sauromys petrophilus ,010603 evolutionary biology ,01 natural sciences ,South Africa ,species richness ,Kalahari ,lcsh:QH301-705.5 ,Molossidae ,Nature and Landscape Conservation ,Ecology ,biology ,010604 marine biology & hydrobiology ,Ecological Modeling ,Scotophilus dinganii ,biology.organism_classification ,Tadarida aegyptiaca ,Agricultural and Biological Sciences (miscellaneous) ,Geography ,lcsh:Biology (General) ,Laephotis botswanae ,Species richness ,Myotis tricolor - Abstract
Kgalagadi Transfrontier Park is located in northwestern South Africa and extends northeastward into Botswana. The park lies largely within the southern Kalahari Desert ecosystem where the Auob and Nassob rivers reach their confluence. Although these rivers run only about once every 100 years, or shortly after large thunderstorms, underground flows and seeps provide consistent surface water for the parks sparse vegetation and diverse wildlife. No formal studies on bats have previously occurred at Kgalagadi. We used SM2 + BAT ultrasonic detectors to survey 10 sites along the Auob and Nassob rivers from 5&ndash, 16 April 2016. The units recorded 3960 call sequences that were analyzed using Kaleidoscope software for South African bats as well as visual determinations based on call structure attributes (low frequency, characteristic frequency, call duration, and bandwidth). We identified 12 species from four families: Rhinolophidae: Rhinolophus fumigatus. Molossidae: Chaerephon pumilus, and Sauromys petrophilus, Tadarida aegyptiaca, Miniopteridae: Miniopteris schreibersi (natalensis), Vespertilionidae: Laephotis botswanae, Myotis tricolor, Neoromicia capensis, N. nana, Pipistrellus hesperidus, Scotophilus dinganii, and S. viridus. The most abundant species during the survey period was N. capensis. We also used paired-site design to test for greater bat activity at water sources compared to dry sites, with dry sites being significantly more active. We conclude that species richness is much higher than previously known from this region and that more species may be present during the warmer months of the year. In addition, activity of bats during the dry season in Kgalagadi would likely be more concentrated around drinking opportunities, thus allowing for better detection of species richness in the area.
- Published
- 2018
- Full Text
- View/download PDF
57. Mercury Bioaccumulation in Two Species of Insectivorous Bats from Urban China: Influence of Species, Age, and Land Use Type
- Author
-
Laura M Heiker, Rick A. Adams, and Claire V Ramos
- Subjects
0106 biological sciences ,Nyctalus ,Male ,China ,Health, Toxicology and Mutagenesis ,chemistry.chemical_element ,010501 environmental sciences ,Biology ,Toxicology ,010603 evolutionary biology ,01 natural sciences ,Animal science ,Species Specificity ,Chiroptera ,Ecotoxicology ,Juvenile ,Animals ,Pipistrellus ,0105 earth and related environmental sciences ,Age Factors ,Insectivore ,Agriculture ,General Medicine ,Mercury ,biology.organism_classification ,Pollution ,Mercury (element) ,chemistry ,Bioaccumulation ,Environmental Pollutants ,Female ,Bioindicator ,Environmental Monitoring - Abstract
Mercury (Hg) is a widespread, toxic pollutant, and China is the world’s largest emitter. We investigated Hg concentrations of fur in Japanese pipistrelles (Pipistrellus abramus) and Chinese noctules (Nyctalus plancyi) from Chengdu, Sichuan Province, in relation to degree of urbanization. Bats were mist-netted in June and July 2013, and the fur was analyzed via atomic absorption. Statistical comparisons were made between ages, species, and site types with unpaired t tests and between Hg concentration and body condition with Spearman’s rank correlations. Across sites, adult pipistrelles (n = 10) had significantly greater concentrations than adult noctules (n = 16). Adult N. plancyi (n = 16) had significantly greater concentrations than juvenile N. plancyi (n = 14). Contrary to our predictions, there was no significant difference in Hg values between urban (n = 3) and peri-urban (n = 6) locations for P. abramus. While small sample sizes precluded additional comparisons, the highest value (33 mg/kg) came from an adult female P. abramus in the agricultural area. The relationship between body condition and Hg concentration was insignificant. However, most pipistrelles (7/13) and no noctules (0/31) had concentrations > 10 mg/kg, a threshold associated with disruption of homeostatic control and mobility. All bats had concentrations > 0.2 mg/kg, which is associated with compromised immunity. These are the first published records of contaminant concentrations from bats in China. For future studies, we recommend P. abramus as a regional bioindicator, longer term assessments of pre- and post-exposure effects, and simultaneous assessment of blood and fur Hg concentrations.
- Published
- 2018
58. Dopaminergic basis for signaling belief updates, but not surprise, and the link to paranoia
- Author
-
Tarik Dahoun, Matthew B. Wall, Rick A. Adams, Thomas H. B. FitzGerald, Raymond J. Dolan, Philipp Schwartenbeck, Matthew M. Nour, Oliver D. Howes, and Christopher Coello
- Subjects
Adult ,Male ,Paranoid Disorders ,0301 basic medicine ,Dopamine ,media_common.quotation_subject ,Culture ,Bayesian probability ,Sensory system ,Receptors, Dopamine ,03 medical and health sciences ,0302 clinical medicine ,medicine ,Humans ,Paranoia ,media_common ,Brain Mapping ,Motivation ,Multidisciplinary ,Ventral striatum ,Dopaminergic ,Brain ,Bayes Theorem ,Magnetic Resonance Imaging ,Surprise ,030104 developmental biology ,medicine.anatomical_structure ,Psychotic Disorders ,PNAS Plus ,Normative ,Female ,medicine.symptom ,Psychology ,030217 neurology & neurosurgery ,medicine.drug ,Cognitive psychology - Abstract
Distinguishing between meaningful and meaningless sensory information is fundamental to forming accurate representations of the world. Dopamine is thought to play a central role in processing the meaningful information content of observations, which motivates an agent to update their beliefs about the environment. However, direct evidence for dopamine’s role in human belief updating is lacking. We addressed this question in healthy volunteers who performed a model-based functional magnetic resonance imaging (fMRI) task designed to separate the neural processing of meaningful and meaningless sensory information. We modelled participant behaviour using a normative Bayesian observer model, and used the magnitude of the model-derived belief update following an observation to quantify its meaningful information content. We also acquired positron emission tomography (PET) imaging measures of dopamine function in the same subjects. We show that the magnitude of belief updates about task structure (meaningful information), but not pure sensory surprise (meaningless information), are encoded in midbrain and ventral striatum activity. Using PET we show that the neural encoding of meaningful information is negatively related to dopamine-2/3 receptor availability in the midbrain and dexamphetamine-induced dopamine release capacity in the striatum. Trial-by-trial analysis of task performance indicated that subclinical paranoid ideation is negatively related to behavioural sensitivity to observations carrying meaningful information about the task structure. The findings provide the first direct evidence implicating dopamine in model-based belief updating in humans, and have implications for understating the pathophysiology of psychotic disorders where dopamine function is disrupted.
- Published
- 2018
59. Human visual exploration reduces uncertainty about the sensed world
- Author
-
M. Berk Mirza, Rick A. Adams, Christoph Mathys, Karl J. Friston
- Published
- 2018
- Full Text
- View/download PDF
60. Bayesian Inference, Predictive Coding, and Computational Models of Psychosis
- Author
-
Rick A. Adams
- Subjects
Computational model ,Psychosis ,Encoding (memory) ,Schizophrenia (object-oriented programming) ,Jumping to conclusions ,medicine ,Inference ,Variance (accounting) ,Bayesian inference ,Psychology ,medicine.disease ,Developmental psychology ,Cognitive psychology - Abstract
The brain is thought to be a hierarchical Bayesian model of its body and its environment that performs inference on the causes of its sensations using predictive coding. In such a model, the accurate encoding of precision (inverse variance) of both prior beliefs and sensory data is essential. If the precision of prior beliefs is reduced, then inference will be biased toward sensory data, e.g., chance events will cause unwarranted updates to higher-level beliefs. In schizophrenia both a hierarchical imbalance in synaptic gain and a loss of inhibitory function (i.e., increased “excitatory/inhibitory balance”) bias inference in this way. This change may underlie the increased learning rate seen in belief updating paradigms in schizophrenia, although this may not be the only contributor to the “jumping to conclusions” bias—a proposed factor in the formation of delusional beliefs. Potential factors underlying the maintenance of delusional beliefs are also discussed, including reversal learning problems, and attempts to model these processes computationally.
- Published
- 2018
61. Contributors
- Author
-
Rick A. Adams, Matthew A. Albrecht, Alan Anticevic, Deanna M. Barch, Albert Compte, Adam Culbreth, Gustavo Deco, Murat Demirtaş, Gregory Dumont, Michael J. Frank, James M. Gold, Boris Gutkin, Jakob Heinzle, Quentin J.M. Huys, John H. Krystal, Reinoud Maex, John D. Murray, Juan P. Ramirez-Mahaluf, P. Read Montague, A.D. Redish, Julia Sheffield, Klaas E. Stephan, Cody J. Walters, James A. Waltz, and Xiao-Jing Wang
- Published
- 2018
62. S192. Characterizing Variation in Connectivity and Behavior in the Psychosis Spectrum: Towards Identifying Individualized Treatments
- Author
-
Rick A. Adams, John D. Murray, Antonija Kolobaric, Joshua B. Burt, Alan Anticevic, Morgan Flynn, Brendan Adkinson, Jie Lisa Ji, and Aleksandar Savić
- Subjects
Psychosis ,Variation (linguistics) ,medicine ,Biology ,medicine.disease ,Biological Psychiatry ,Cognitive psychology - Published
- 2019
63. Maternity Roost Selection by Fringed Myotis in Colorado
- Author
-
Mark A. Hayes and Rick A. Adams
- Subjects
Strength of evidence ,Geography ,Ecology ,biology ,Myotis thysanodes ,biology.organism_classification ,Ecology, Evolution, Behavior and Systematics ,Multimodel inference - Abstract
Fringed myotis (Myotis thysanodes) is a bat species of conservation concern in western North America that may be impacted by increased recreational activity near roost sites, changes in water resource availability caused by increased urban and agricultural water use, and anthropogenic climate change. Our purpose was to describe and model maternity roost use by fringed myotis in Colorado. We compared differences between roosts occupied by maternal fringed myotis and randomly selected potential roosting locations that were not known to be occupied by this species during the maternity period. We evaluated the strength of evidence for competing hypotheses on 2 scales: one that included landscape variables and a second that included roost-site variables. We used logistic regression, Akaike's information criterion, and multimodel inference to investigate maternity roost use by fringed myotis. The model explaining the most variability in our landscape data included grade and aspect, and the model expla...
- Published
- 2015
64. Postnatal ontogeny of the cochlea and flight ability in Jamaican fruit bats (Phyllostomidae) with implications for the evolution of echolocation
- Author
-
Richard T. Carter and Rick A. Adams
- Subjects
Histology ,Human echolocation ,Biology ,Sonar ,Chiroptera ,otorhinolaryngologic diseases ,Animals ,Molecular Biology ,Ecology, Evolution, Behavior and Systematics ,Cochlea ,Call structure ,Cell Biology ,Anatomy ,Adaptation, Physiological ,Biological Evolution ,Sonar system ,Basilar membrane ,Evolutionary biology ,Echolocation ,Flight, Animal ,Postnatal ontogeny ,Secondary spiral lamina ,Original Article ,sense organs ,Developmental Biology - Abstract
Recent evidence has shown that the developmental emergence of echolocation calls in young bats follow an independent developmental pathway from other vocalizations and that adult-like echolocation call structure significantly precedes flight ability. These data in combination with new insights into the echolocation ability of some shrews suggest that the evolution of echolocation in bats may involve inheritance of a primitive sonar system that was modified to its current state, rather than the ad hoc evolution of echolocation in the earliest bats. Because the cochlea is crucial in the sensation of echoes returning from sonar pulses, we tracked changes in cochlear morphology during development that included the basilar membrane (BM) and secondary spiral lamina (SSL) along the length of the cochlea in relation to stages of flight ability in young bats. Our data show that the morphological prerequisite for sonar sensitivity of the cochlea significantly precedes the onset of flight in young bats and, in fact, development of this prerequisite is complete before parturition. In addition, there were no discernible changes in cochlear morphology with stages of flight development, demonstrating temporal asymmetry between the development of morphology associated with echo-pulse return sensitivity and volancy. These data further corroborate and support the hypothesis that adaptations for sonar and echolocation evolved before flight in mammals.
- Published
- 2015
65. Geographic and Elevational Distribution of Fringed Myotis (Myotis thysanodes) in Colorado
- Author
-
Mark A. Hayes and Rick A. Adams
- Subjects
Geographic distribution ,Geography ,Ecology ,biology ,business.industry ,Elevation ,Distribution (economics) ,Myotis thysanodes ,Myotis myotis ,biology.organism_classification ,business ,Ecology, Evolution, Behavior and Systematics - Abstract
Fringed myotis (Myotis thysanodes) is considered a bat species of conservation concern in Colorado and in western North America. The purpose of our research was to describe the geographic and elevational distribution of fringed myotis in Colorado and consider the potential influence of the Southern Rocky Mountains on the distribution of this species. We documented, mapped, and analyzed 729 Colorado capture and occurrence records for this species, and used 546 records in a 2-way ANOVA comparing elevational distribution among sex and reproductive classes. Mean elevation of occurrence was significantly different among reproductive classes (F = 7.03, P = 0.0010) but not between sex classes (F = 0.10, P = 0.7578). These elevation results support the hypothesis that fringed myotis tend not to occur at higher elevations in the Southern Rockies. Mapped occurrence records suggest that fringed myotis exhibits a bifurcated geographic distribution, with separate populations occurring in a band along the Col...
- Published
- 2014
66. Computational Psychiatry
- Author
-
Robb B. Rutledge and Rick A. Adams
- Subjects
0301 basic medicine ,03 medical and health sciences ,030104 developmental biology ,0302 clinical medicine ,030217 neurology & neurosurgery - Published
- 2017
67. SU72. Abnormal Frontal Synaptic Gain Mediating the P300 in Patients With Psychosis and Their Unaffected Relatives
- Author
-
Álvaro Díez, Dimitris A. Pinotsis, Mei-Hua Hall, Siri Ranlund, Angel Nevado, Madiha Shaikh, Elvira Bramon, Stella Calafato, Muriel Walshe, Rick A. Adams, and Karl J. Friston
- Subjects
Psychosis ,medicine.diagnostic_test ,Functional integration (neurobiology) ,business.industry ,Cognition ,Electroencephalography ,medicine.disease ,Psychiatry and Mental health ,Abstracts ,medicine ,GABAergic ,In patient ,Left superior ,Genetic risk ,business ,Neuroscience ,Cognitive psychology - Abstract
Background: The “dysconnection hypothesis” of psychosis suggests that a disruption of functional integration underlies cognitive deficits and clinical symptoms. Impairments in the P300 potential are well documented in psychosis. We investigated intrinsic (self-)connectivity in a cortical hierarchy during a P300 experiment. We used Dynamic Causal Modeling to estimate how evoked activity results from the dynamics of coupled neural populations and how neural coupling changes with the experimental factors. Methods: Twenty-four patients with psychosis, 24 unaffected relatives, and 25 controls underwent EEG recordings during an auditory oddball paradigm. We analyzed 16 frontoparietal models (primary auditory, superior parietal, and superior frontal sources) and identified an optimal model of neural coupling, explaining diagnosis and genetic risk effects, as well as their interactions with task condition. Results: The winning model included changes in connectivity at all 3 hierarchical levels. Patients showed decreased self-inhibition (ie, increased cortical excitability) in left superior frontal gyrus across task conditions, compared to unaffected participants. Relatives had similar increases in excitability in left superior frontal and right superior parietal sources, and a reversal of the normal synaptic gain changes in response to targets, relative to standard tones. Conclusion: We confirmed that both subjects with psychosis and their relatives show a context-independent loss of synaptic gain control at the highest levels of the hierarchy. The relatives also showed abnormal gain modulation responses to task-relevant stimuli. These may be caused by NMDA-receptor and/or GABAergic pathologies that change the excitability of superficial pyramidal cells and may be a potential biological marker for psychosis.
- Published
- 2017
68. Megachiropteran bats profoundly unique from microchiropterans in climbing and walking locomotion: Evolutionary implications
- Author
-
Richard T. Carter and Rick A. Adams
- Subjects
030110 physiology ,0106 biological sciences ,0301 basic medicine ,Arboreal locomotion ,Physiology ,lcsh:Medicine ,Phyllostomatidae ,Walking ,01 natural sciences ,Gait (human) ,Functional abilities ,Chiroptera ,Bats ,Medicine and Health Sciences ,Wings, Animal ,medicine.vector_of_disease ,lcsh:Science ,Musculoskeletal System ,Microchiroptera ,Mammals ,Multidisciplinary ,Fruit Bats ,Eukaryota ,Anatomy ,Climbing ,Biological Evolution ,Biomechanical Phenomena ,Hindlimb ,Vertebrates ,Flight (Biology) ,Locomotion ,Research Article ,medicine.medical_specialty ,Biology ,010603 evolutionary biology ,Pteropodidae ,Vertical surfaces ,03 medical and health sciences ,Physical medicine and rehabilitation ,medicine ,Animals ,Skeleton ,Biological Locomotion ,lcsh:R ,Organisms ,Biology and Life Sciences ,Humerus ,Shoulders ,Amniotes ,lcsh:Q ,human activities - Abstract
Understandably, most locomotor analyses of bats have focused on flight mechanics and behaviors. However, we investigated nonflight locomotion in an effort to glean deeper insights into the evolutionary history of bats. We used high-speed video (300 Hz) to film and compare walking and climbing mechanics and kinematics between several species of the suborders Megachiroptera (Pteropodidae) versus Microchiroptera (Vespertilionidae and Phyllostomatidae). We found fundamentally distinctive behaviors, functional abilities, and performance outcomes between groups, but nearly homogeneous outcomes within groups. Megachiropterans exhibited climbing techniques and skills not found in microchiropterans and which aligned with other fully arboreal mammals. Megachiropterans climbed readily when placed in a head-up posture on a vertical surface, showed significantly greater ability than microchiropterans to abduct and extend the reach of their limbs, and climbed at a greater pace by using a more aggressive ipsilateral gait, at times being supported by only a single contact point. In addition, megachiropterans showed little ability to employ basic walking mechanics when placed on the ground, also a pattern observed in some highly adapted arboreal mammals. Conversely, microchiropterans resisted climbing vertical surfaces in a head-up posture, showed significantly less extension of their limbs, and employed a less-aggressive, slower contralateral gait with three points of contact. When walking, microchiropterans used the same gait they did when climbing which is representative of basic tetrapod terrestrial mechanics. Curiously, megachiropterans cycled their limbs significantly faster when climbing than when attempting to walk, whereas microchiropterans cycled their limbs at significantly faster rates when walking than when climbing. We contend that nonflight locomotion mechanics give a deep evolutionary view into the ancestral es locomotor platform on which flight was built in each of these groups.
- Published
- 2017
69. Loss of sensory attenuation in patients with functional (psychogenic) movement disorders
- Author
-
Rick A. Adams, Marco Davare, Atsuo Nuruki, Harriet R. Brown, Isabel Pareés, Mark J. Edwards, Karl J. Friston, and Kailash P. Bhatia
- Subjects
Adult ,Male ,medicine.medical_specialty ,Movement Disorders ,Movement disorders ,Sense of agency ,Movement (music) ,Index finger ,Middle Aged ,Hand ,Hospital Anxiety and Depression Scale ,medicine.anatomical_structure ,Physical medicine and rehabilitation ,Somatosensory Disorders ,medicine ,Humans ,Psychogenic disease ,Female ,Neurology (clinical) ,Functional movement disorder ,medicine.symptom ,Psychology ,Functional movement ,Aged - Abstract
Functional movement disorders require attention to manifest yet patients report the abnormal movement to be out of their control. In this study we explore the phenomenon of sensory attenuation, a measure of the sense of agency for movement, in this group of patients by using a force matching task. Fourteen patients and 14 healthy control subjects were presented with forces varying from 1 to 3 N on the index finger of their left hand. Participants were required to match these forces; either by pressing directly on their own finger or by operating a robot that pressed on their finger. As expected, we found that healthy control subjects consistently overestimated the force required when pressing directly on their own finger than when operating a robot. However, patients did not, indicating a significant loss of sensory attenuation in this group of patients. These data are important because they demonstrate that a fundamental component of normal voluntary movement is impaired in patients with functional movement disorders. The loss of sensory attenuation has been correlated with the loss of sense of agency, and may help to explain why patients report that they do not experience the abnormal movement as voluntary. * Abbreviations : FMD : functional movement disorder HADS : Hospital Anxiety and Depression Scale PDI : Peters Delusions Inventory
- Published
- 2014
70. Ontogeny of the Larynx and Flight Ability in Jamaican Fruit Bats (Phyllostomidae) With Considerations for the Evolution of Echolocation
- Author
-
Richard T. Carter and Rick A. Adams
- Subjects
Larynx ,Histology ,biology ,Ontogeny ,Shrew ,Human echolocation ,Anatomy ,medicine.disease ,biology.organism_classification ,Sorex vagrans ,Laryngeal calcification ,medicine.anatomical_structure ,Cricoid cartilage ,biology.animal ,medicine ,Ecology, Evolution, Behavior and Systematics ,Biotechnology ,Calcification - Abstract
Echolocating bats have adaptations of the larynx such as hypertrophied intrinsic musculature and calcified or ossified cartilages to support sonar emission. We examined growth and development of the larynx relative to developing flight ability in Jamaican fruit bats to assess how changes in sonar production are coordinated with the onset of flight during ontogeny as a window for understanding the evolutionary relationships between these systems. In addition, we compare the extent of laryngeal calcification in an echolocating shrew species (Sorex vagrans) and the house mouse (Mus musculus), to assess what laryngeal chiropteran adaptations are associated with flight versus echolocation. Individuals were categorized into one of five developmental flight stages (flop, flutter, flap, flight, and adult) determined by drop-tests. Larynges were cleared and stained with alcian blue and alizarin red, or sectioned and stained with hematoxylin and eosin. Our results showed calcification of the cricoid cartilage in bats, represented during the flap stage and this increased significantly in individuals at the flight stage. Thyroid and arytenoid cartilages showed no evidence of calcification and neither cricoid nor thyroid showed significant increases in rate of growth relative to the larynx as a whole. The physiological cross-sectional area of the cricothyroid muscles increased significantly at the flap stage. Shrew larynges showed signs of calcification along the margins of the cricoid and thyroid cartilages, while the mouse larynx did not. These data suggest the larynx of echolocating bats becomes stronger and sturdier in tandem with flight development, indicating possible developmental integration between flight and echolocation.
- Published
- 2014
71. Ontogeny of vocalization in <scp>J</scp> amaican fruit bats with implications for the evolution of echolocation
- Author
-
J. B. Shaw, R. T. Carter, and Rick A. Adams
- Subjects
Perch ,biology ,Sweep rate ,Ecology ,Ontogeny ,Evolutionary developmental biology ,Zoology ,Animal Science and Zoology ,Human echolocation ,biology.organism_classification ,Sonar ,Ecology, Evolution, Behavior and Systematics ,Artibeus - Abstract
A long-standing question in bat biology is if the evolution of echolocation and flight are associated or if they evolved independently, and if so, which evolved first. We seek to use ontogeny as a surrogate for understanding linkages between flight evolution and echolocation in bats. To do this we quantify the onset of recognizable sonar calls in newborn Artibeus jamaicensis and the tempo of growth and development across several different postnatal flight stages. By dropping individuals from a perch beginning on day 1 postpartum, we recorded vocalizations and quantified their flight ability into five developmental stages (flop, flutter, flap, flight and adult). One-day-old individuals were capable of emitting sonar-like frequency-modulated (FM) calls during free-fall that were not significantly different from adult sonar calls in high and low frequency (kHz). However, bandwidth (kHz) did increase significantly with age as did sweep rate (kHz ms−1), whereas call duration significantly decreased. Few bats older than 18 days emitted communication calls as they fell and measured parameters of communication calls did not change significantly with age. Our data support the hypothesis that communication and sonar calls are discrete and independently derived at birth and thus have different evolutionary pathways as well.
- Published
- 2014
72. Bayesian inference, predictive coding and delusions
- Author
-
Rick A. Adams, Karl J. Friston, and Harriet R. Brown
- Subjects
Psychosis ,Cognitive Neuroscience ,General Arts and Humanities ,media_common.quotation_subject ,Perspective (graphical) ,General Social Sciences ,Inference ,medicine.disease ,Bayesian inference ,Developmental psychology ,Bayes' theorem ,Schizophrenia ,Perception ,medicine ,Normative ,Psychology ,Cognitive psychology ,media_common - Abstract
This paper considers psychotic symptoms in terms of false inferences or beliefs. It is based on the notion that the brain is an organ of inference that actively constructs hypotheses to explain or predict its sensations. This perspective provides a normative (Bayes optimal) account of action and perception that emphasises probabilistic representations; in particular, the confidence or precision of beliefs about the world. We consider sensory attenuation deficits, catatonia and delusions as various expressions of the same core pathology: namely, an aberrant encoding of precision in a predictive coding hierarchy. In predictive coding, precision is thought to be encoded by the postsynaptic gain of neurons reporting prediction error. This suggests that both pervasive trait abnormalities and florid failures of inference in the psychotic state can be linked to factors controlling postsynaptic gain—such as NMDA receptor function and (dopaminergic) neuromodulation. We illustrate these points using a biologically plausible simulation of attribution of agency—showing how a reduction in the precision of prior beliefs, relative to sensory evidence, can lead to false inference.
- Published
- 2014
73. Dopamine modulates belief updating but not surprise in the midbrain and ventral striatum
- Author
-
Raymond J. Dolan, Thomas H. B. FitzGerald, Christopher Coello, Tarik Dahoun, Oliver D. Howes, Rick A. Adams, Matthew B. Wall, Philipp Schwartenbeck, and Matthew M. Nour
- Subjects
Pharmacology ,Psychosis ,medicine.diagnostic_test ,Ventral striatum ,Dopaminergic ,Substantia nigra ,medicine.disease ,Ventral tegmental area ,Psychiatry and Mental health ,medicine.anatomical_structure ,Neurology ,Salience (neuroscience) ,Dopamine ,medicine ,Pharmacology (medical) ,Neurology (clinical) ,Psychology ,Functional magnetic resonance imaging ,Neuroscience ,Biological Psychiatry ,medicine.drug - Abstract
Dopamine may be critical for processing the meaningful information content of observations, which drives belief updating about the (hidden) states of the world [1–3]. In human functional magnetic resonance imaging (fMRI) studies, neuronal activity encoding the magnitude of belief updates has been detected in dopamine-rich midbrain regions, namely the substantia nigra and ventral tegmental area (SN/VTA) [1-3]. Yet, there is no direct evidence linking dopamine function to belief updating signals in humans. This question is relevant to our understanding of the relationship between dopamine, aberrant inference and the generation of psychotic symptoms such as paranoia [4]. We investigated the dopaminergic basis of belief update signals using fMRI and positron emission tomography (PET) imaging. 39 healthy participants (mean age 26y, 22 male) performed an fMRI task that decomposed sensory information into information-theoretic surprise (unexpected but not necessarily meaningful information content) and Bayesian surprise (magnitude of belief updates due to meaningful information) [1]. A Bayesian observer computational model was fitted to participants’ behavior, allowing the derivation of trial-wise regressors for information-theoretic and Bayesian surprise for fMRI analysis. 36 participants also had a [11C]-(+)-4-propyl-9-hydroxy-naphthoxazine ([11C]-(+)-PHNO) PET scan to quantify dopamine-2/3 receptor (D2/3R) availability. 17 participants additionally had a second [11C]-(+)-PHNO PET scan 3hrs following 0.5mg/kg oral dexamphetamine, to quantify striatal dopamine release capacity. Our analyses focused on the relationship between measures of neuronal activity (fMRI) and dopamine function (PET) in the bilateral SN/VTA complex and ventral striatum (VS). Our computational model closely predicted participant behaviour (R2= .67), and there was a negative correlation between subclinical paranoid thoughts and the degree to which participant behavior approximated the predictions of an ideal Bayesian observer (rho = -0.60, P Our results indicate that the SN/VTA and VS are involved in processing the meaningful information of observations, as reflected in Bayesian belief updating [1-3]. Crucially, we provide direct evidence that neuronal signals encoding (unsigned) belief updates depend on dopaminergic activity, at variance with classical interpretations of dopamine function in terms of (signed) reward prediction errors. Moreover, our results suggest that a reduced behavioural sensitivity to meaningful information is related to subclinical paranoia. Together, these results are highly relevant for dopaminergic theories of psychosis, such as the aberrant salience hypothesis, which posit that mesostriatal dopamine dysfunction results in the formation of false beliefs about the causes of sensory information, leading to hallucinations and delusions [4].
- Published
- 2018
74. M42 A TRANSCRIPTOME-WIDE ASSOCIATION STUDY OF MISMATCH NEGATIVITY
- Author
-
Rick A. Adams, Karl J. Friston, Anjali Bhat, Johan H. Thygesen, Aritz Irizar, Elvira Bramon, Elliot Hong, Jasmine Harju-Seppänen, Karoline Kuchenbaecker, Baihan Wang, Mei-Hua Hall, Eirini Zartaloudi, Oliver Pain, Isabelle Austin-Zimmerman, and Stella Calafato
- Subjects
Pharmacology ,Genetics ,Transcriptome ,Psychiatry and Mental health ,Neurology ,Mismatch negativity ,Pharmacology (medical) ,Neurology (clinical) ,Biology ,Association (psychology) ,Biological Psychiatry - Published
- 2019
75. T180. Impaired Theta Phase-Coupling Between Hippocampus and Medial Prefrontal Cortex in Schizophrenia
- Author
-
Rick A. Adams, Dan Bush, Sofie S. Meyer, Fanfan Zheng, Stelios Orfanos, and Neil Burgess
- Subjects
Phase coupling ,business.industry ,Schizophrenia ,Medicine ,Hippocampus ,business ,medicine.disease ,Prefrontal cortex ,Neuroscience ,Biological Psychiatry - Published
- 2019
76. Unique Insights into Dispersion Distances Among Calling Males of Wahlberg’s Epauletted Fruit Bat in Kruger National Park, South Africa
- Author
-
Rick A. Adams and Emily R. Snode
- Subjects
Epomophorus wahlbergi ,Novel technique ,Ficus sycomorus ,biology ,National park ,Ecology ,Food availability ,Foraging ,biology.organism_classification ,food.food ,Pteropodidae ,food ,Large group ,General Environmental Science - Abstract
In June 2009, we used a novel technique to quantify dispersion patterns among a large group of calling male Epomophorus wahlbergi congregated around five neighboring and synchronously fruiting sycamore fig trees (Ficus sycomorus) in Kruger National Park, South Africa by using the physics of sound attenuation over distance to monitor and map positions of calling males without disturbing their mating behavior. The lack of fruiting sycamore fig trees across the area concentrated males among five fruiting trees along a 10 km stretch of riverine corridor that paralleled the river road. We hypothesized that the patterns of dispersion among calling males would be clumped in relation to fruiting fig trees that attract foraging females. Results show that the distribution of calling perches were clumped (R = 0.75) as opposed to randomly or equally dispersed. In addition, we found that a 2 km section of the corridor contained the majority of calling males and in this area calling males were more tightly clumped (R = 0.58) than across the other 6 kms of corridor. In addition, distances among calling males and their nearest neighbor were significantly less on average (25m) in the higher- density area, than in the lower density areas (315m)(P < 0.001). Although most males were near fruiting figs, they maintained a minimum dispersion and never were observed calling from the same tree. In addition, some males appeared dominant over others and consistently positioned themselves closest to ripe fig trees where females were foraging. Our data give previously unobserved insights into how male Wahlberg's epauletted fruit bats position their calling roosts in relation to one another and fruiting fig trees under conditions of extreme drought and limited local food availability.
- Published
- 2013
77. First physical record of Allen's lappet-browed bat (Idionycteris phyllotis) in Colorado
- Author
-
Rick A. Adams and Ron Lambeth
- Subjects
Geography ,Adult female ,biology ,Picnic ,Idionycteris phyllotis ,biology.organism_classification ,Archaeology ,Ecology, Evolution, Behavior and Systematics - Abstract
We report on the first physical record for Allen's lappet-browed bat (Idionycteris phyllotis) in Colorado. The lone adult female was hanging on a rafter of a picnic structure at James M. Robb State Park, Mesa County, Colorado, on 25 July 2014. On 30 July, the bat was hanging in the same position and was deceased. Our report extends the distribution of this species north by 100 km and east by 15 km.
- Published
- 2015
78. Abnormal frontoparietal synaptic gain mediating the P300 in patients with psychotic disorder and their unaffected relatives
- Author
-
Álvaro, Díez, Siri, Ranlund, Dimitris, Pinotsis, Stella, Calafato, Madiha, Shaikh, Mei-Hua, Hall, Muriel, Walshe, Ángel, Nevado, Karl J, Friston, Rick A, Adams, and Elvira, Bramon
- Subjects
Adult ,Male ,Psychiatric Status Rating Scales ,Brain Mapping ,Adolescent ,Models, Neurological ,Prefrontal Cortex ,Bayes Theorem ,Electroencephalography ,Middle Aged ,Event-Related Potentials, P300 ,Article ,Young Adult ,Nonlinear Dynamics ,Psychotic Disorders ,Humans ,Family ,Female ,Nerve Net ,Aged - Abstract
The "dysconnection hypothesis" of psychosis suggests that a disruption of functional integration underlies cognitive deficits and clinical symptoms. Impairments in the P300 potential are well documented in psychosis. Intrinsic (self-)connectivity in a frontoparietal cortical hierarchy during a P300 experiment was investigated. Dynamic Causal Modeling was used to estimate how evoked activity results from the dynamics of coupled neural populations and how neural coupling changes with the experimental factors. Twenty-four patients with psychotic disorder, twenty-four unaffected relatives, and twenty-five controls underwent EEG recordings during an auditory oddball paradigm. Sixteen frontoparietal network models (including primary auditory, superior parietal, and superior frontal sources) were analyzed and an optimal model of neural coupling, explaining diagnosis and genetic risk effects, as well as their interactions with task condition were identified. The winning model included changes in connectivity at all three hierarchical levels. Patients showed decreased self-inhibition-that is, increased cortical excitability-in left superior frontal gyrus across task conditions, compared with unaffected participants. Relatives had similar increases in excitability in left superior frontal and right superior parietal sources, and a reversal of the normal synaptic gain changes in response to targets relative to standard tones. It was confirmed that both subjects with psychotic disorder and their relatives show a context-independent loss of synaptic gain control at the highest hierarchy levels. The relatives also showed abnormal gain modulation responses to task-relevant stimuli. These may be caused by NMDA-receptor and/or GABAergic pathologies that change the excitability of superficial pyramidal cells and may be a potential biological marker for psychosis. Hum Brain Mapp 38:3262-3276, 2017. © 2017 Wiley Periodicals, Inc.
- Published
- 2016
79. Active inference, eye movements and oculomotor delays
- Author
-
Karl J. Friston, Rick A. Adams, Laurent Perrinet, Institut de Neurosciences de la Timone (INT), Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS), Wellcome Trust Centre for Neuroimaging, University College of London [London] (UCL), European Project: 269921,EC:FP7:ICT,FP7-ICT-2009-6,BRAINSCALES(2011), Perrinet, Laurent, and Brain-inspired multiscale computation in neuromorphic hybrid systems - BRAINSCALES - - EC:FP7:ICT2011-01-01 - 2015-03-31 - 269921 - VALID
- Subjects
tracking eye movements ,Computer science ,Inference ,perception ,050105 experimental psychology ,Smooth pursuit ,Bayesian filtering ,03 medical and health sciences ,Cellular and Molecular Neuroscience ,0302 clinical medicine ,Dependency graph ,active inference ,Oculomotor delays ,0501 psychology and cognitive sciences ,[SDV.NEU] Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC] ,variational free energy ,business.industry ,General Neuroscience ,05 social sciences ,Probabilistic logic ,Eye movement ,Kalman filter ,Optimal control ,generalized coordinates ,Generative model ,FOS: Biological sciences ,Quantitative Biology - Neurons and Cognition ,Poster Presentation ,Neurons and Cognition (q-bio.NC) ,[SDV.NEU]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC] ,Artificial intelligence ,smooth pursuit eye movements ,business ,030217 neurology & neurosurgery ,Biotechnology ,Computer Science(all) - Abstract
We consider the problem of sensorimotor delays in the optimal control of (smooth) eye movements under uncertainty. Specifically, we consider delays in the visuo-oculomotor loop and their implications for active inference. Active inference uses a generalisation of Kalman filtering to provide Bayes optimal estimates of hidden states and action in generalised coordinates of motion. Representing hidden states in generalised coordinates provides a simple way of compensating for both sensory and oculomotor delays. The efficacy of this scheme is illustrated using neuronal simulations of pursuit initiation responses, with and without compensation. We then consider an extension of the generative model to simulate smooth pursuit eye movements - in which the system believes both the target and its centre of gaze are attracted to a (fictive) point moving in the visual field. Finally, the generative model is equipped with a hierarchical structure, so that it can recognise and remember unseen (occluded) trajectories and emit anticipatory responses. These simulations speak to a straightforward and neurobiologically plausible solution to the generic problem of integrating information from different sources with different temporal delays and the particular difficulties encountered when a system - like the oculomotor system - tries to control its environment with delayed signals. Figure 1 This schematic shows the dependencies among various quantities modelling exchanges of an agent with the environment. It shows the states of the environment and the system in terms of a probabilistic dependency graph, where connections denote directed ...
- Published
- 2016
80. Longitudinal peripheral blood transcriptional analysis of a patient with severe Ebola virus disease
- Author
-
Jeffery K. Taubenberger, John M. Dye, David Baxter, John C. Kash, Kathie-Anne Walters, Jason Kindrachuk, Rick D. Adams, Andrew S. Herbert, Matthew J. Memoli, Krisztina Janosko, Daniel S. Chertow, Kelsey Scherler, Rebekah M. James, Richard T. Davey, and Spencer W. Stonier
- Subjects
0301 basic medicine ,myalgia ,viruses ,Disease ,medicine.disease_cause ,Virus Replication ,Article ,Sierra leone ,Disease Outbreaks ,03 medical and health sciences ,0302 clinical medicine ,Immune system ,Coagulopathy ,Leukocytes ,Medicine ,Humans ,030212 general & internal medicine ,Longitudinal Studies ,Ebola virus ,business.industry ,Organ dysfunction ,General Medicine ,Hemorrhagic Fever, Ebola ,medicine.disease ,Ebolavirus ,030104 developmental biology ,Immunology ,RNA, Viral ,medicine.symptom ,business ,Viral load - Abstract
The 2013-2015 outbreak of Ebola virus disease in Guinea, Liberia, and Sierra Leone was unprecedented in the number of documented cases, but there have been few published reports on immune responses in clinical cases and their relationships with the course of illness and severity of Ebola virus disease. Symptoms of Ebola virus disease can include severe headache, myalgia, asthenia, fever, fatigue, diarrhea, vomiting, abdominal pain, and hemorrhage. Although experimental treatments are in development, there are no current U.S. Food and Drug Administration-approved vaccines or therapies. We report a detailed study of host gene expression as measured by microarray in daily peripheral blood samples collected from a patient with severe Ebola virus disease. This individual was provided with supportive care without experimental therapies at the National Institutes of Health Clinical Center from before onset of critical illness to recovery. Pearson analysis of daily gene expression signatures revealed marked gene expression changes in peripheral blood leukocytes that correlated with changes in serum and peripheral blood leukocytes, viral load, antibody responses, coagulopathy, multiple organ dysfunction, and then recovery. This study revealed marked shifts in immune and antiviral responses that preceded changes in medical condition, indicating that clearance of replicating Ebola virus from peripheral blood leukocytes is likely important for systemic viral clearance.
- Published
- 2016
81. Scene Construction, Visual Foraging, and Active Inference
- Author
-
M Berk, Mirza, Rick A, Adams, Christoph D, Mathys, and Karl J, Friston
- Subjects
active inference ,visual search ,Hypothesis and Theory ,information gain ,Bayesian inference ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,epistemic value ,salience ,free energy ,Neuroscience ,scene construction - Abstract
This paper describes an active inference scheme for visual searches and the perceptual synthesis entailed by scene construction. Active inference assumes that perception and action minimize variational free energy, where actions are selected to minimize the free energy expected in the future. This assumption generalizes risk-sensitive control and expected utility theory to include epistemic value; namely, the value (or salience) of information inherent in resolving uncertainty about the causes of ambiguous cues or outcomes. Here, we apply active inference to saccadic searches of a visual scene. We consider the (difficult) problem of categorizing a scene, based on the spatial relationship among visual objects where, crucially, visual cues are sampled myopically through a sequence of saccadic eye movements. This means that evidence for competing hypotheses about the scene has to be accumulated sequentially, calling upon both prediction (planning) and postdiction (memory). Our aim is to highlight some simple but fundamental aspects of the requisite functional anatomy; namely, the link between approximate Bayesian inference under mean field assumptions and functional segregation in the visual cortex. This link rests upon the (neurobiologically plausible) process theory that accompanies the normative formulation of active inference for Markov decision processes. In future work, we hope to use this scheme to model empirical saccadic searches and identify the prior beliefs that underwrite intersubject variability in the way people forage for information in visual scenes (e.g., in schizophrenia).
- Published
- 2016
82. Brain Computations in Schizophrenia
- Author
-
Rick A. Adams and Karl J. Friston
- Subjects
Generative model ,medicine.anatomical_structure ,Interneuron ,Salience (neuroscience) ,medicine ,GABAergic ,Sensory system ,Cognition ,Hippocampal formation ,Psychology ,Bayesian inference ,Neuroscience ,Cognitive psychology - Abstract
© 2016 Elsevier Inc. All rights reserved. Because the brain performs Bayesian inference for the causes of its sensory data, the synaptic gain could encode the precision (inverse variance) of its beliefs using a hierarchical generative model and predictive coding. Several neurobiological risk factors for schizophrenia (NMDAR and GABAergic interneuron hypofunction) reduce both synaptic and "oscillatory" gain at high hierarchical areas. This could impair the encoding of precision at higher levels of the brain's hierarchical model and increase expected precision at lower levels. This imbalance can account for many neurobiological and phenomenological findings in schizophrenia. Striatal D 2 R hyperactivity may increase the precision of current policies by inhibiting behavioral or cognitive switching. This could be a (dysfunctional) consequence of or even an attempt to compensate for prefrontal or hippocampal pathology. This D 2 R hyperactivity may also reduce learning from positive outcomes and affect the encoding of motivational (or informational) salience.
- Published
- 2016
83. A Bayesian account of ‘hysteria’
- Author
-
Rick A. Adams, Isabel Pareés, Mark J. Edwards, Harriet R. Brown, and Karl J. Friston
- Subjects
media_common.quotation_subject ,Hysteria ,Inference ,Poison control ,Sensory system ,sensorimotor information processing ,Models, Psychological ,Bayesian inference ,Models, Biological ,050105 experimental psychology ,Developmental psychology ,03 medical and health sciences ,cognitive neuroscience ,0302 clinical medicine ,Perception ,Functional neurological symptom disorder ,medicine ,Humans ,0501 psychology and cognitive sciences ,Occasional Paper ,media_common ,05 social sciences ,Brain ,Cognition ,Bayes Theorem ,medicine.disease ,attention ,Neurology (clinical) ,Percept ,Psychology ,Psychological Theory ,030217 neurology & neurosurgery ,Cognitive psychology - Abstract
This article provides a neurobiological account of symptoms that have been called ‘hysterical’, ‘psychogenic’ or ‘medically unexplained’, which we will call functional motor and sensory symptoms. We use a neurobiologically informed model of hierarchical Bayesian inference in the brain to explain functional motor and sensory symptoms in terms of perception and action arising from inference based on prior beliefs and sensory information. This explanation exploits the key balance between prior beliefs and sensory evidence that is mediated by (body focused) attention, symptom expectations, physical and emotional experiences and beliefs about illness. Crucially, this furnishes an explanation at three different levels: (i) underlying neuromodulatory (synaptic) mechanisms; (ii) cognitive and experiential processes (attention and attribution of agency); and (iii) formal computations that underlie perceptual inference (representation of uncertainty or precision). Our explanation involves primary and secondary failures of inference; the primary failure is the (autonomous) emergence of a percept or belief that is held with undue certainty (precision) following top-down attentional modulation of synaptic gain. This belief can constitute a sensory percept (or its absence) or induce movement (or its absence). The secondary failure of inference is when the ensuing percept (and any somatosensory consequences) is falsely inferred to be a symptom to explain why its content was not predicted by the source of attentional modulation. This account accommodates several fundamental observations about functional motor and sensory symptoms, including: (i) their induction and maintenance by attention; (ii) their modification by expectation, prior experience and cultural beliefs and (iii) their involuntary and symptomatic nature.
- Published
- 2012
84. Tacaribe Virus Causes Fatal Infection of An Ostensible Reservoir Host, the Jamaican Fruit Bat
- Author
-
Richard A. Bowen, Charles H. Calisher, Tony Schountz, David W. Gardiner, Stephanie James, Ann C. Cogswell-Hawkinson, and Rick A. Adams
- Subjects
Male ,Disease reservoir ,Immunology ,Virulence ,Biology ,medicine.disease_cause ,Microbiology ,Virus ,Virology ,Arenaviridae Infections ,Chiroptera ,medicine ,Animals ,Arenaviridae ,Artibeus ,Disease Reservoirs ,Transmission (medicine) ,Inoculation ,Rabies virus ,biology.organism_classification ,Trinidad and Tobago ,Insect Science ,Pathogenesis and Immunity ,Female - Abstract
Tacaribe virus (TCRV) was first isolated from 11 Artibeus species bats captured in Trinidad in the 1950s during a rabies virus surveillance program. Despite significant effort, no evidence of infection of other mammals, mostly rodents, was found, suggesting that no other vertebrates harbored TCRV. For this reason, it was hypothesized that TCRV was naturally hosted by artibeus bats. This is in stark contrast to other arenaviruses with known hosts, all of which are rodents. To examine this hypothesis, we conducted experimental infections of Jamaican fruit bats ( Artibeus jamaicensis ) to determine whether they could be persistently infected without substantial pathology. We subcutaneously or intranasally infected bats with TCRV strain TRVL-11573, the only remaining strain of TCRV, and found that low-dose (10 4 50% tissue culture infective dose [TCID 50 ]) inoculations resulted in asymptomatic and apathogenic infection and virus clearance, while high-dose (10 6 TCID 50 ) inoculations caused substantial morbidity and mortality as early as 10 days postinfection. Uninoculated cage mates failed to seroconvert, and viral RNA was not detected in their tissues, suggesting that transmission did not occur. Together, these data suggest that A. jamaicensis bats may not be a reservoir host for TCRV.
- Published
- 2012
- Full Text
- View/download PDF
85. Molecular and Phylogenetic Characterization of Cytokine Genes from Seba's Short-Tailed Bat (Carollia perspicillata)
- Author
-
Mitchell E. McGlaughlin, Charles H. Calisher, Rick A. Adams, Ann C. Cogswell-Hawkinson, and Tony Schountz
- Subjects
Carollia perspicillata ,biology ,Phylogenetic tree ,Immunology ,Immunology and Allergy ,Zoology ,Cytokine genes ,biology.organism_classification - Published
- 2011
86. Bat reproduction declines when conditions mimic climate change projections for western North America
- Author
-
Rick A. Adams
- Subjects
education.field_of_study ,Hot Temperature ,Time Factors ,Reproductive success ,Environmental change ,Ecology ,Range (biology) ,Climate Change ,Reproduction ,Population Dynamics ,Population ,Climate change ,Insectivore ,Geography ,Pregnancy ,Chiroptera ,North America ,Animals ,Female ,Ecosystem ,Precipitation ,education ,Ecology, Evolution, Behavior and Systematics - Abstract
Climate change models predict that much of western North America is becoming significantly warmer and drier, resulting in overall reductions in availability of water for ecosystems. Herein, I demonstrate that significant declines in the reproductive success of female insectivorous bats occur in years when annual environmental conditions mimic the long-term predictions of regional climate change models. Using a data set gathered on bat populations from 1996 through 2008 along the Front Range of Colorado, I compare trends in population numbers and reproductive outcomes of six species of vespertilionid bats with data on mean annual high temperature, precipitation, snow pack, and stream discharge rates. I show that levels of precipitation and flow rates of small streams near maternity colonies is fundamentally tied to successful reproduction in female bats, particularly during the lactation phase. Across years that experienced greater than average mean temperatures with less than average precipitation and stream flow, bat populations responded by slight to profound reductions in reproductive output depending on the severity of drought conditions. In particular, reproductive outputs showed profound declines (32-51%) when discharge rates of the largest stream in the field area dropped below 7 m 3 /s, indicating a threshold response. Such sensitivity to environmental change portends severe impacts to regional bat populations if current scenarios for climate change in western North America are accurate. In addition, bats act as early-warning indicators of large-scale ecological effects resulting from further regional warming and drying trends currently at play in western North America.
- Published
- 2010
87. S9. RESTING EEG CHANGES IN SCHIZOPHRENIA
- Author
-
Rick A. Adams, Leonhardt Unruh, Alan Anticevic, and L. Elliot Hong
- Subjects
03 medical and health sciences ,Psychiatry and Mental health ,Abstracts ,Poster Session III ,0302 clinical medicine ,Text mining ,business.industry ,Medicine ,business ,Neuroscience ,Resting eeg ,030217 neurology & neurosurgery ,030227 psychiatry - Abstract
Background Numerous previous studies have found increased power in low frequencies in resting EEG data in subjects with a diagnosis of schizophrenia (Scz). Low frequency power in δ is usually localised to frontal channels, whereas increases in θ power can be more widespread (Boutros et al., 2008). Given the low spatial resolution of EEG data, we used a spatial filter (the surface Laplacian) to investigate whether differences in resting EEG frequency band power in Scz are truly distributed throughout the cortex, or whether they localise to more focal areas. Methods 64 channel EEG data were recorded for 5 minutes in both eyes closed and eyes open conditions in 103 medicated Scz (M=71, F=32, mean(std) age=40(14.3) yrs) and 104 controls (M=64, F=30, mean(std) age=40(13.8) yrs). The data were epoched and epochs with artefacts were detected by their amplitude, variance or kurtosis and removed. The power spectral density at each channel was computed using Welch’s method, and the surface Laplacian (using the spherical spline method of Perrin et al. (1987, 1989)) was applied to reduce volume conduction effects and improve topographical localization. Power was analysed separately for five frequency bands: δ (2–4 Hz), θ (4–8 Hz), α (8–12 Hz), β (15–30 Hz) and γ (30–50 Hz). Permutation testing (20 runs of 1000 group label permutations) was performed with correction for multiple comparisons based on clusters of channels of significantly different (p0.05). Scz had greater θ power in both eyes open and eyes closed conditions using cluster-based permutation tests (both p
- Published
- 2018
88. S154. THE ROLE OF DOPAMINE IN PROCESSING THE MEANINGFUL INFORMATION OF OBSERVATIONS, AND IMPLICATIONS FOR THE ABERRANT SALIENCE HYPOTHESIS OF SCHIZOPHRENIA
- Author
-
Rick A. Adams, Raymond J. Dolan, Christopher Coello, Oliver D. Howes, Matthew M. Nour, Thomas H. B. FitzGerald, Philipp Schwartenbeck, Matthew B. Wall, and Tarik Dahoun
- Subjects
Poster Session III ,medicine.diagnostic_test ,Ventral striatum ,030227 psychiatry ,Associative learning ,Ventral tegmental area ,Abstracts ,03 medical and health sciences ,Psychiatry and Mental health ,Bayes' theorem ,0302 clinical medicine ,medicine.anatomical_structure ,Neuroimaging ,Salience (neuroscience) ,Dopamine ,medicine ,Functional magnetic resonance imaging ,Psychology ,Neuroscience ,030217 neurology & neurosurgery ,medicine.drug - Abstract
Background The aberrant salience hypothesis of schizophrenia proposes that symptoms such as paranoia arise when behavioural salience is attributed to neutral stimuli. Mesolimbic dopamine dysfunction is thought to be central to this mechanism; building on findings that activity in this pathway conveys a (signed) reward prediction error signal. Given that many psychotic symptoms are not explicitly related to reward learning, it is relevant that recent studies in rodents have demonstrated a role for midbrain dopamine neurons in value-neutral associative learning. Direct evidence for this role in humans, however, is lacking. In this study we asked whether the mesolimbic dopamine circuit is involved in encoding the value-neutral meaningful information of observations, using a model-based functional magnetic resonance imaging (fMRI) task and dopamine positron emission tomography (PET). We define ‘meaningful information’ as the degree to which an observation results in a belief-update to an agent’s internal model of the environment (Kullback-Leibler divergence from prior to posterior beliefs; ‘Bayesian surprise’). Methods Participants were tasked to infer the current (hidden) state of the environment, using partially-informative observations at each trial, and then report their belief at the end of each trial. Participant beliefs were modelled using a Hidden Markov Model of the task and iterative application of Bayes’ rule, allowing us to quantify the Bayesian surprise (meaningful information content) associated with a trial observation. Crucially, our task de-correlated Bayesian surprise from both the pure sensory unexpectedness of an observation (unexpected but meaningless information) and its signed reward prediction error. 39 healthy participants (22M, mean age 26y) performed 180 task trials within an fMRI scanner. 36 participants also had a [11C]-(+)-4-propyl-9-hydroxy-naphthoxazine (PHNO) PET scan to quantify dopamine-2/3 receptor (D2/3R) availability. 17 participants additionally had a second PET scan 3hrs post 0.5mg/kg oral dexamphetamine, to quantify striatal dopamine release capacity. Neuroimaging analyses were restricted to the bilateral substantia nigra/ventral tegmental area (SN/VTA) and ventral striatum (VS). Results Our computational model closely predicted participant behaviour (R2= .67), and there was a negative correlation between subclinical paranoia and the degree to which participant behaviour approximated normative Bayesian performance (rho = -.60, P
- Published
- 2018
89. Water availability and successful lactation by bats as related to climate change in arid regions of western North America
- Author
-
Mark A. Hayes and Rick A. Adams
- Subjects
Greenhouse Effect ,Evening ,media_common.quotation_subject ,Wildlife ,Climate change ,Biology ,Animal science ,Chiroptera ,Animals ,Lactation ,Ecosystem ,Ecology, Evolution, Behavior and Systematics ,media_common ,Ecology ,Temperature ,Water ,Humidity ,biology.organism_classification ,Arid ,Water resources ,Habitat ,North America ,Female ,Animal Science and Zoology ,Myotis thysanodes ,Reproduction - Abstract
1. Climate change in North America is happening at an accelerated rate, reducing availability of water resources for bats and other wildlife that require it for successful reproduction. 2. We test the water-needy lactation hypotheses directly by tracking the drinking habitats of individual lactating and non-reproductive female fringed myotis at an artificial water source located near a maternity roost. 3. We used a submerged passive integrative transponder (PIT) tag reader system designed to track fish to instead record numbers of water source visitations by tagged bats. 4. Of 24 PIT-tagged adult females, 16 (67%) were detected repeatedly by the plate antenna as they passed to drink between 18 July and 28 August 2006. 5. The total number of drinking passes by lactating females (n = 255) were significantly higher than those of non-reproductive adult females (n = 22). Overall, lactating females visited 13 times more often to drink water than did non-reproductive females. On average, lactating females visited six times more often per night. Drinking bouts occurred most frequently just after evening emergence and at dawn. 6. Drinking patterns of non-reproductive females correlated significantly with fluctuating ambient temperature and relative humidity recorded at the water source, whereas lactating females drank extensively regardless of ambient conditions. 7. We provide a mathematical model to predict the rate of decline in bat populations in the arid West in relation to climate change models for the region.
- Published
- 2008
90. Prenatal Growth and Development in the Angolan Free-tailed Bat, Mops condylurus (Chiroptera: Molossidae)
- Author
-
Karl A. Wyant and Rick A. Adams
- Subjects
Wing ,Ecology ,biology ,Free-tailed bat ,Ossification ,Mops condylurus ,Vertebrate ,biology.organism_classification ,Skull ,medicine.anatomical_structure ,Evolutionary biology ,biology.animal ,Genetics ,medicine ,Animal Science and Zoology ,medicine.symptom ,Molossidae ,Heterochrony ,Ecology, Evolution, Behavior and Systematics ,Nature and Landscape Conservation - Abstract
We present data on prenatal growth, development, and skeletal ossification for the Angolan free-tailed bat (Mops condylurus), a species distributed throughout sub-Saharan Africa. Specimens were measured for crown‐rump length (CRL), greatest length of the skull (GLS), forearm length, mass, and wing area. We cleared and differentially stained specimens for cartilage and bone to quantify pattern of skeletogenesis. Significant regressions for general growth trajectories were generated by plotting CRL and fetal mass against GLS. We quantified growth of the forearm, which showed a positive relationship with growth of the skull. Curiously, wing area was highly positively related to fetal mass, suggesting an ecomorphological relationship of wing loading and flight ability being established early in development in this species. Patterns of ossification in this species were more similar to those of phyllostomid and pteropodid bats than they were to vespertilionid bats, to which M. condylurus is apparently more closely related. In this paper, we provide the 1st published account of prenatal growth, development, and skeletal ossification for the Angolan free-tailed bat, Mops condylurus (Chiroptera: Molossidae). Understanding developmental patterns provides key insights into the evolution of form and function as well as the origins of key evolutionary innovations (Jablonka and Lamb 1998). Indeed, heterochronic shifts in developmental timing are in large part responsible for the evolutionary diversity of the vertebrate limb (Smith 2003).
- Published
- 2007
91. Patterns of anterior cingulate activation in schizophrenia: a selective review
- Author
-
Rick A. Adams and Anthony S. David
- Subjects
medicine.medical_specialty ,positron emission tomography ,medicine.diagnostic_test ,business.industry ,Confounding ,Reviews ,Cognition ,General Medicine ,medicine.disease ,functional magnetic resonance imaging ,behavioral disciplines and activities ,schizophrenia ,anterior cingulate cortex ,medicine.anatomical_structure ,Schizophrenia ,Positron emission tomography ,Functional neuroimaging ,medicine ,business ,Functional magnetic resonance imaging ,Psychiatry ,Neuroscience ,psychological phenomena and processes ,Anterior cingulate cortex - Abstract
Background Anterior cingulate cortex (ACC) dysfunction is implicated in schizophrenia by numerous strands of scientific investigation. Functional neuroimaging studies of the ACC in schizophrenia have shown task-related hypo-activation, hyper-activation, and normal activation relative to comparison subjects. Interpreting these results and explaining their inconsistencies has been hindered by our ignorance of the healthy ACC's function. This review aims to clarify the site and magnitude of ACC activations in schizophrenia, and sources of their variation. Method 48 studies of mnemonic and executive task-related activations in schizophrenia using both positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) were analyzed. Results Abnormal activations in schizophrenia were not restricted to the "cognitive" part of the ACC. Hypoactivations were most common, and were found in all types of tasks. Hyperac-tivations when found, were largely in n-back tasks. Conclusions Hypoactivations cannot be explained by poor performance, more demanding control conditions or chronicity of illness alone. Patients on anti-psychotic medication tended to show both greater ACC activation and better performance, although whether this is directly due to their medication or the resultant reduction in symptoms is unclear. The relationship between ACC rCBF and task performance is not straightforward. Future research should better control confounding factors and incorporate different levels of difficulty.
- Published
- 2007
92. Impaired prefrontal synaptic gain in people with psychosis and their relatives during the mismatch negativity
- Author
-
Katja Schulze, Dimitris A. Pinotsis, Sabrina Petrella, Siri Ranlund, Rick A. Adams, Elvira Bramon, Anirban Dutt, Colm McDonald, Amparo Maestro Carbayo, Karl J. Friston, Miguel Constante, Mei-Hua Hall, Muriel Walshe, Madiha Shaikh, and Álvaro Díez
- Subjects
Male ,prediction-error ,Mismatch negativity ,auditory sensory memory ,genetic risk ,evoked-responses ,0302 clinical medicine ,cortical gain ,psychosis ,Evoked potential ,Research Articles ,bipolar disorder ,Radiological and Ultrasound Technology ,Electroencephalography ,Middle Aged ,unaffected relatives ,schizophrenic-patients ,medicine.anatomical_structure ,Neurology ,Schizophrenia ,Evoked Potentials, Auditory ,Female ,Anatomy ,Pyramidal cell ,Psychology ,Research Article ,Adult ,dcm ,Psychosis ,nmda receptor ,Adolescent ,effective connectivity ,Prefrontal Cortex ,Contingent Negative Variation ,Inhibitory postsynaptic potential ,behavioral disciplines and activities ,Young Adult ,03 medical and health sciences ,Glutamatergic ,visual-cortex ,medicine ,Humans ,frequency oscillations ,Family ,Radiology, Nuclear Medicine and imaging ,dynamic causal modeling ,healthy-volunteers ,functional-anatomy ,cortical excitability ,Models, Theoretical ,medicine.disease ,030227 psychiatry ,schizophrenia ,Acoustic Stimulation ,Nonlinear Dynamics ,Psychotic Disorders ,Brain Injuries ,Endophenotype ,Neurology (clinical) ,Neuroscience ,030217 neurology & neurosurgery - Abstract
The mismatch negativity (MMN) evoked potential, a preattentive brain response to a discriminable change in auditory stimulation, is significantly reduced in psychosis. Glutamatergic theories of psychosis propose that hypofunction of NMDA receptors (on pyramidal cells and inhibitory interneurons) causes a loss of synaptic gain control. We measured changes in neuronal effective connectivity underlying the MMN using dynamic causal modeling (DCM), where the gain (excitability) of superficial pyramidal cells is explicitly parameterised. EEG data were obtained during a MMN task—for 24 patients with psychosis, 25 of their first‐degree unaffected relatives, and 35 controls—and DCM was used to estimate the excitability (modeled as self‐inhibition) of (source‐specific) superficial pyramidal populations. The MMN sources, based on previous research, included primary and secondary auditory cortices, and the right inferior frontal gyrus. Both patients with psychosis and unaffected relatives (to a lesser degree) showed increased excitability in right inferior frontal gyrus across task conditions, compared to controls. Furthermore, in the same region, both patients and their relatives showed a reversal of the normal response to deviant stimuli; that is, a decrease in excitability in comparison to standard conditions. Our results suggest that psychosis and genetic risk for the illness are associated with both context‐dependent (condition‐specific) and context‐independent abnormalities of the excitability of superficial pyramidal cell populations in the MMN paradigm. These abnormalities could relate to NMDA receptor hypofunction on both pyramidal cells and inhibitory interneurons, and appear to be linked to the genetic aetiology of the illness, thereby constituting potential endophenotypes for psychosis. Hum Brain Mapp 37:351–365, 2016. © 2015 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.
- Published
- 2015
93. Use of Existing Diagnostic Reverse-Transcription Polymerase Chain Reaction Assays for Detection of Ebola Virus RNA in Semen
- Author
-
Lisa E. Hensley, Elizabeth S. Higgs, Peter B. Jahrling, James Pettitt, and Rick D. Adams
- Subjects
0301 basic medicine ,Male ,Emergency Use Authorization ,Sexual transmission ,viruses ,Semen ,Biology ,medicine.disease_cause ,law.invention ,03 medical and health sciences ,Major Articles and Brief Reports ,law ,Virology ,medicine ,Immunology and Allergy ,Humans ,Polymerase chain reaction ,Ebolavirus ,Ebola virus ,Reverse Transcriptase Polymerase Chain Reaction ,Ebola virus RNA ,virus diseases ,Hemorrhagic Fever, Ebola ,Reverse transcription polymerase chain reaction ,030104 developmental biology ,Infectious Diseases - Abstract
Sexual transmission of Ebola virus in Liberia has now been documented and associated with new clusters in regions previously declared Ebola free. Assays that have Emergency Use Authorization (EUA) and are routinely used to detect Ebola virus RNA in whole blood and plasma specimens at the Liberian Institute for Biomedical Research were tested for their suitability in detecting the presence of Ebola virus RNA in semen. Qiagen AVL extraction protocols, as well as the Ebola Zaire Target 1 and major groove binder quantitative reverse-transcription polymerase chain reaction assays, were demonstrably suitable for this purpose and should facilitate epidemiologic investigations, including those involving long-term survivors of Ebola.
- Published
- 2015
94. Age-related changes in working memory and the ability to ignore distraction
- Author
-
Robb B. Rutledge, Peter Smittenaar, Raymond J. Dolan, Peter Zeidman, Fiona McNab, Rick A. Adams, and Harriet R. Brown
- Subjects
Adult ,Aging ,Analysis of Variance ,Multidisciplinary ,Working memory ,Poison control ,Middle Aged ,Biological Sciences ,behavioral disciplines and activities ,Developmental psychology ,Neural activity ,Memory, Short-Term ,Video Games ,Encoding (memory) ,Age related ,Distraction ,Humans ,Attention ,Healthy aging ,Prefrontal cortex ,Psychology ,Aged ,Cognitive psychology - Abstract
Significance We reveal a novel and highly significant change in how items are held in mind in healthy aging. Using smartphones, data were collected from 29,631 participants, between the ages of 18–69 y. We compare the ability to exclude distractors when items are entered into working memory (WM) (encoding distraction, ED) and when items are held in mind (delay distraction, DD). In older adults, WM in the absence of distraction was more similar to ED exclusion than DD exclusion. A greater reliance on focused attention during encoding may reflect compensation for the more pronounced deterioration we observed in DD exclusion in older age. This can inform other areas of cognition and strategies to ameliorate or manage debilitating age-related cognitive decline.
- Published
- 2015
95. Proactive and reactive response inhibition across the lifespan
- Author
-
Harriet R. Brown, Raymond J. Dolan, Rick A. Adams, Peter Zeidman, Glyn Lewis, Robb B. Rutledge, and Peter Smittenaar
- Subjects
Adult ,Male ,Aging ,Adolescent ,lcsh:Medicine ,Stimulus (physiology) ,Neuropsychological Tests ,Brain mapping ,050105 experimental psychology ,03 medical and health sciences ,Executive Function ,Young Adult ,0302 clinical medicine ,Sex Factors ,Inhibitory control ,Reaction Time ,Medicine ,Humans ,0501 psychology and cognitive sciences ,Young adult ,Healthy aging ,lcsh:Science ,Response inhibition ,Aged ,Reactive control ,Brain Mapping ,Multidisciplinary ,Reactive inhibition ,business.industry ,05 social sciences ,lcsh:R ,Age Factors ,Reactive Inhibition ,Middle Aged ,Video Games ,lcsh:Q ,Female ,Smartphone ,business ,Neuroscience ,030217 neurology & neurosurgery ,Psychomotor Performance ,Research Article - Abstract
One expression of executive control involves proactive preparation for future events, and this contrasts with stimulus driven reactive control exerted in response to events. Here we describe findings from a response inhibition task, delivered using a smartphone-based platform, that allowed us to index proactive and reactive inhibitory self-control in a large community sample (n = 12,496). Change in stop-signal reaction time (SSRT) when participants are provided with advance information about an upcoming trial, compared to when they are not, provides a measure of proactive control while SSRT in the absence of advance information provides a measure of reactive control. Both forms of control rely on overlapping frontostriatal pathways known to deteriorate in healthy aging, an age-related decline that occurs at an accelerated rate in men compared to women. Here we ask whether these patterns of age-related decline are reflected in similar changes in proactive and reactive inhibitory control across the lifespan. As predicted, we observed a decline in reactive control with natural aging, with a greater rate of decline in men compared to women (~10 ms versus ~8 ms per decade of adult life). Surprisingly, the benefit of preparation, i.e. proactive control, did not change over the lifespan and women showed superior proactive control at all ages compared to men. Our results suggest that reactive and proactive inhibitory control partially rely on distinct neural substrates that are differentially sensitive to age-related change.
- Published
- 2015
96. Active Inference, Predictive Coding and Cortical Architecture
- Author
-
Karl J. Friston, Rick A. Adams, and André M. Bastos
- Subjects
Structure (mathematical logic) ,Hierarchy (mathematics) ,Computer science ,business.industry ,Process (engineering) ,Message passing ,Key (cryptography) ,Inference ,Artificial intelligence ,business ,Generative grammar ,Free energy principle - Abstract
This chapter discusses how many features of cortical anatomy and physiology can be understood in the light of a predictive coding theory of brain function. In Sect. 7.1, we briefly discuss the theoretical reasons to suppose that the brain is likely to use predictive coding. One key theoretical underpinning of predictive coding is the free energy principle, which argues that brains must maximize the evidence for their (generative) model of sensory inputs: a process of ‘active inference’. In Sect. 7.2, we discuss how active inference predicts commonalities in the extrinsic connections of sensory and motor systems. Such commonalities are found in their hierarchical structure (shown by laminar characteristics), their topography, their pharmacology and physiology. In Sect. 7.3, we show how the equations describing hierarchical message passing within a predictive coding scheme can be mapped on to key features of intrinsic connections, namely the canonical cortical microcircuit, and their implications for the oscillatory dynamics of different cell populations. In Sect. 7.4, we briefly review some empirical evidence for predictive coding in the brain.
- Published
- 2015
97. Temporal resource partitioning by bats at water holes
- Author
-
Rick A. Adams and Katherine M. Thibault
- Subjects
Water resources ,Resource (biology) ,Water hole ,Ecology ,Significant difference ,Niche ,Animal Science and Zoology ,BAT activity ,Biology ,Arid ,Ecology, Evolution, Behavior and Systematics - Abstract
The temporal axis of niche (temporally based resource partitioning) is an understudied mechanism for resource partitioning in mammals even though it provides a potential means for species coexistence. Herein we evaluate species-specific use curves based upon capture times during the overlapping activity of bat species at two water holes in an arid environment where bats likely suffer high levels of evaporative water loss during roosting. During the first 75 min after sunset, intense bat activity at each water hole ensued and, although visitation times overlapped, there was a significant difference among species use curves. In addition, pairwise comparisons showed high similarity in temporal visitation patterns across sites for species in which capture numbers were comparable, whereas other species shifted to significantly earlier arrival times when their capture numbers were higher. There were no significant differences in mean roost site emergence times among species, nor in distance of roost sites from water holes. Our data provide one of the few statistically verified examples of fine-grain temporal partitioning by mammals simultaneously using the same resource. We conclude that temporal partitioning helps facilitate bat species coexistence in water-stressed environments.
- Published
- 2006
98. Into the Night
- Author
-
Rick Adams, Rick A. Adams, Rick Adams, and Rick A. Adams
- Subjects
- Scientific expeditions, Naturalists--Biography, Wildlife watching, Nocturnal animals, Biology--Fieldwork, Biologists--Biography, Natural history--Fieldwork
- Abstract
This entertaining collection of essays from professional scientists and naturalists provides an enlightening look at the lives of field biologists with a passion for the hidden world of nocturnal wildlife. Into the Night explores the harrowing, fascinating, amusing, and largely unheard personal experiences of scientists willing to forsake the safety of daylight to document the natural history of these uniquely adapted animals. Contributors tell of confronting North American bears, cougars, and rattlesnakes; suffering red ctenid spider bites in the tropical rain forest; swimming through layers of feeding-frenzied hammerhead sharks in the Galapagos; evading the wrath of African bull elephants in South Africa; and delighting in the curious and gentle nature of foxes and unconditional acceptance by a family of owls. They describe “fire in the sky” across a treeless tundra, a sea ablaze with bioluminescent algae, nighttime earthquakes on the Pacific Rim, and hurricanes and erupting volcanoes on a Caribbean island. Into the Night reveals rare and unexpected insights into nocturnal field research, illuminating experiences, discoveries, and challenges faced by intrepid biologists studying nature's nightly marvels across the globe. This volume will be of interest to scientists and general readers alike.
- Published
- 2013
99. Bat Evolution, Ecology, and Conservation
- Author
-
Rick A. Adams, Scott C. Pedersen, Rick A. Adams, and Scott C. Pedersen
- Subjects
- Bats--Evolution, Bats, Bats--Conservation
- Abstract
Recent advances in the study of bats have changed the way we understand this illusive group of mammals. This volume consist of 25 chapters and 57 authors from around the globe all writing on the most recent finding on the evolution, ecology and conservation of bats. The chapters in this book are not intended to be exhaustive literature reviews, but instead extended manuscripts that bring new and fresh perspectives. Many chapters consist of previously unpublished data and are repetitive of new insights and understanding in bat evolution, ecology and conservation. All chapters were peer-reviewed and revised by the authors. Many of the chapters are multi-authored to provide comprehensive and authoritative coverage of the topics.
- Published
- 2013
100. Calcium as a limiting resource to insectivorous bats: can water holes provide a supplemental mineral source?
- Author
-
Brad Petru, Scott C. Pedersen, Rick A. Adams, Katherine M. Thibault, and Jenna Jadin
- Subjects
Lasiurus ,Ecology ,chemistry.chemical_element ,Zoology ,Insectivore ,Limiting ,Biology ,Calcium ,biology.organism_classification ,Lasionycteris noctivagans ,Myotis ciliolabrum ,chemistry ,Eptesicus fuscus ,Calcium content ,Animal Science and Zoology ,Ecology, Evolution, Behavior and Systematics - Abstract
Data are presented on a bat assemblage captured among 10 water holes in Colorado over 5 years. The assemblage consists of Myotis ciliolabrum, M. evotis, M. lucifugus, M. thysanodes, M. volans, Eptesicus fuscus, Lasiurus cinereus, Lasionycteris noctivagans and Corynorhinus townsendii .R esults show that reproductive females and juveniles are captured in higher frequencies at water holes containing higher water hardness and that water hardness correlates highly significantly with dissolved calcium content. Also presented are laboratory test data on the stomach volume of Eptesicus fuscus that provide a model for understanding the effect of dissolved calcium content in water as a significant resource. These data indicate that water holes provide supplemental sources of calcium for bats not provided by diet.
- Published
- 2003
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.