Search

Our goal was to estimate the diagnostic accuracy of substantia nigra fractional anisotropy (SN-FA) for Parkinson’s disease (PD) diagnosis in a sample similar to the clinical setting, including patients with essential tremor (ET) and healthy controls (HC). We also performed a systematic review and meta-analysis to estimate mean change in SN-FA induced by PD and its diagnostic accuracy. Our sample consisted of 135 subjects: 72 PD, 21 ET and 42 HC. To address inter-scanner variability, two 3.0-T MRI scans were performed. MRI results of this sample were pooled into a meta-analysis that included 1,432 subjects (806 PD and 626 HC). A bivariate model was used to evaluate diagnostic accuracy measures. In our sample, we did not observe a significant effect of disease on SN-FA and it was uninformative for diagnosis. The results of the meta-analysis estimated a 0.03 decrease in mean SN-FA in PD relative to HC (CI: 0.01–0.05). However, the discriminatory capability of SN-FA to diagnose PD was low: pooled sensitivity and specificity were 72 % (CI: 68–75) and 63 % (CI: 58–70), respectively. There was high heterogeneity between studies (I2 = 91.9 %). SN-FA cannot be used as an isolated measure to diagnose PD. • SN-FA appears insufficiently sensitive and specific to diagnose PD. • Radiologists must be careful when translating mean group results to clinical practice. • Imaging protocol and analysis standardization is necessary for developing reproducible quantitative biomarkers.

Functional brain hubs are key integrative regions in brain networks. Recently, brain hubs identified through resting-state fMRI have emerged as interesting targets to increase understanding of the relationships between large-scale functional networks and psychopathology. However, few studies have directly addressed the replicability and consistency of the hub regions identified and their association with symptoms. Here, we used the eigenvector centrality (EVC) measure obtained from graph analysis of two large, independent population-based samples of children and adolescents (7–15 years old; total N = 652; 341 subjects for site 1 and 311 for site 2) to evaluate the replicability of hub identification. Subsequently, we tested the association between replicable hub regions and psychiatric symptoms. We identified a set of hubs consisting of the anterior medial prefrontal cortex and inferior parietal lobule/intraparietal sulcus (IPL/IPS). Moreover, lower EVC values in the right IPS were associated with psychiatric symptoms in both samples. Thus, low centrality of the IPS was a replicable sign of potential vulnerability to mental disorders in children. The identification of critical and replicable hubs in functional cortical networks in children and adolescents can foster understanding of the mechanisms underlying mental disorders.

One of the major challenges facing psychiatry is how to incorporate biological measures in the classification of mental health disorders. Many of these disorders affect brain development and its connectivity. In this study, we propose a novel method for assessing brain networks based on the combination of a graph theory measure (eigenvector centrality) and a one-class support vector machine (OC-SVM).We applied this approach to resting-state fMRI data from 622 children and adolescents. Eigenvector centrality (EVC) of nodes from positive- and negative-task networks were extracted from each subject and used as input to an OC-SVM to label individual brain networks as typical or atypical. We hypothesised that classification of these subjects regarding the pattern of brain connectivity would predict the level of psychopathology.Subjects with atypical brain network organisation had higher levels of psychopathology (p 0.001). There was a greater EVC in the typical group at the bilateral posterior cingulate and bilateral posterior temporal cortices; and significant decreases in EVC at left temporal pole.The combination of graph theory methods and an OC-SVM is a promising method to characterise neurodevelopment, and may be useful to understand the deviations leading to mental disorders.

Saccades were assessed in 21 adults (age 24 years, SD = 4) and 15 children (age 11 years, SD = 1), using combined functional magnetic resonance imaging (fMRI) and eye-tracking. Subjects visually tracked a point on a horizontal line in four conditions: time and position predictable task (PRED), position predictable (pPRED), time predictable (tPRED) and visually guided saccades (SAC). Both groups in the PRED but not in pPRED, tPRED and SAC produced predictive saccades with latency below 80 ms. In task versus group comparisons, children's showed less efficient learning compared to adults for predictive saccades (adults = 48%, children = 34%, p = 0.05). In adults brain activation was found in the frontal and occipital regions in the PRED, in the intraparietal sulcus in pPRED and in the frontal eye field, posterior intraparietal sulcus and medial regions in the tPRED task. Group-task interaction was found in the supplementary eye field and visual cortex in the PRED task, and the frontal cortex including the right frontal eye field and left frontal pole, in the pPRED condition. These results indicate that, the basic visuomotor circuitry is present in both adults and children, but fine-tuning of the activation according to the task temporal and spatial demand mature late in child development.

Drowning is a serious and frequently neglected public health threat. Primary respiratory impairment after submersion often leads to brain dysfunction. Depending on the period of global hypoxia (respiratory failure), clinical aspects of neurological dysfunction are evident on the first evaluation after the water rescue. Nowadays, many neuropsychological assessments after drowning are inconclusive, with some studies reporting only minor neurological or cognitive impairments. The aim of this study is to identify measures in neuropsychological tests that most contribute to classify volunteers as moderate drowning subjects or healthy controls. To the best of our knowledge, this study is the first neuropsychological prospective case-control study of moderate drowning in a country with large coastal cities.Fifteen moderate drowning patients (DP), who met the inclusion criteria, were compared with 18 healthy controls (HC). All subjects were assessed on memory, learning, visual spatial ability, executive function, attention, and general intellectual functioning and underwent structural magnetic resonance (MR) imaging of the brain at 3.0 T, in order to exclude subjects with anatomic abnormalities.Neuropsychological tests assessing learning, execution function, and verbal fluency-Rey Auditory Verbal Learning Test (RAVLT) general learning ability, Digit Span total, Phonological Verbal Fluency (total FAS correct), and Brief Visuospatial Memory Test Revised (BVMT) correct recognition-have the strongest discriminating ability, using predictive models via the partial least squares (PLS) approach for data classification, while the other tests have shown similar predictive values between groups.Learning, execution function, and verbal fluency domains were the most critically affected domains. Serious impairments in the same domains have already been reported in severe drowning cases, and we hypothesize that subtle alterations found in moderate drowning cases, although not sufficient to be detected in daily routine, may possibly have a negative impact on cognitive reserve.

Investigations of brain maturation processes are a key step to understand the cognitive and emotional changes of adolescence. Although structural imaging findings have delineated clear brain developmental trajectories for typically developing individuals, less is known about the functional changes of this sensitive development period. Developmental changes, such as abstract thought, complex reasoning, and emotional and inhibitory control, have been associated with more prominent cortical control. The aim of this study is to assess brain networks connectivity changes in a large sample of 7- to 15-year-old subjects, testing the hypothesis that cortical regions will present an increasing relevance in commanding the global network. Functional magnetic resonance imaging (fMRI) data were collected in a sample of 447 typically developing children from a Brazilian community sample who were submitted to a resting state acquisition protocol. The fMRI data were used to build a functional weighted graph from which eigenvector centrality (EVC) was extracted. For each brain region (a node of the graph), the age-dependent effect on EVC was statistically tested and the developmental trajectories were estimated using polynomial functions. Our findings show that angular gyrus become more central during this maturation period, while the caudate; cerebellar tonsils, pyramis, thalamus; fusiform, parahippocampal and inferior semilunar lobe become less central. In conclusion, we report a novel finding of an increasing centrality of the angular gyrus during the transition to adolescence, with a decreasing centrality of many subcortical and cerebellar regions.

Made available in DSpace on 2015-11-03T15:28:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-07-01. Added 1 bitstream(s) on 2015-11-04T10:15:20Z : No. of bitstreams: 1 S0004-282X2014000700510.pdf: 281636 bytes, checksum: d5eab2edc6fa8d79bb88291c5f8daacb (MD5) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) CInAPCe Program Estudos recentes têm sugerido possível relação entre epilepsia do lobo temporal com esclerose mesial temporal (MTS) e neurocisticercose (NC). Conduzimos um estudo caso-controle para avaliar a associação de NC e MTS. Método: Selecionamos randomicamente pacientes com diferentes tipos de epilepsia, incluindo: MTS, epilepsia primariamente generalizada (PGE) e epilepsia focal sintomática (FSE). Pacientes foram submetidos a uma entrevista estruturada, seguida por uma tomografia computadorizada de crânio (CT). Um neuroradiologista avaliou as imagens quanto à presença de lesões calcificadas sugestivas de NC. Resultados das CT foram comparados com os dados dos pacientes. Resultados: Mais pacientes do grupo MTS apresentaram lesões calcificadas sugestivas de NC que de outros grupos (p=0,002). Na análise multivariável, MTS foi um preditor independente de uma ou mais calcificações sugestivas de NC (p=0,033). Conclusão: Após controlar para fatores confusionais, encontramos uma associação independente entre lesões calcificadas de NC e MTS. Recent studies have suggested a possible relationship between temporal lobe epilepsy with mesial temporal sclerosis (MTS) and neurocysticercosis (NC). We performed a case-control study to evaluate the association of NC and MTS. Method: : We randomly selected patients with different epilepsy types, including: MTS, primary generalized epilepsy (PGE) and focal symptomatic epilepsy (FSE). Patients underwent a structured interview, followed by head computed tomography (CT). A neuroradiologist evaluated the scan for presence of calcified lesions suggestive of NC. CT results were matched with patients'data. Results: : More patients in the MTS group displayed calcified lesions suggestive of NC than patients in the other groups (p=0.002). On multivariate analysis, MTS was found to be an independent predictor of one or more calcified NC lesions (p=0.033). Conclusion: : After controlling for confounding factors, we found an independent association between NC calcified lesions and MTS. Universidade de São Paulo, Departamento de Neurologia, Faculdade de Medicina Universidade de São Paulo, Instituto de Radiologia, Hospital das Clínicas Universidade Estadual Paulista, Departamento e Bioestatística, Instituto de Biociências de Botucatu FAPESP: 2008/04119-4 CInAPCe Program: 2005/56464-9

Abnormal connectivity patterns have frequently been reported as involved in pathological mental states. However, most studies focus on “static,” stationary patterns of connectivity, which may miss crucial biological information. Recent methodological advances have allowed the investigation of dynamic functional connectivity patterns that describe non‐stationary properties of brain networks. Here, we introduce a novel graphical measure of dynamic connectivity, called time‐varying eigenvector centrality (tv‐EVC). In a sample 655 children and adolescents (7–15 years old) from the Brazilian “High Risk Cohort Study for Psychiatric Disorders” who were imaged using resting‐state fMRI, we used this measure to investigate age effects in the temporal in control and default‐mode networks (CN/DMN). Using support vector regression, we propose a network maturation index based on the temporal stability of tv‐EVC. Moreover, we investigated whether the network maturation is associated with the overall presence of behavioral and emotional problems with the Child Behavior Checklist. As hypothesized, we found that the tv‐EVC at each node of CN/DMN become more stable with increasing age (P

Schizophrenia is a neurodevelopmental disorder that produces abnormalities across different brain regions. Measuring structural covariance with MRI is a well-established approach to investigate common changes in distinct systems. We investigated structural covariance in schizophrenia in a large Brazilian sample of individuals with chronic schizophrenia (n = 143), First Episode Psychosis (n = 32), and matched healthy controls (n = 82) using a combination of graph analysis and computational neuroanatomy. Firstly, we proposed the connectivity-closeness and integrity-closeness centrality measures and them compared healthy controls with chronic schizophrenia regarding these metrics. We then conducted a second analysis on the mapped regions comparing the pairwise difference between the three groups. Our results show that compared with controls, both patient groups (in pairwise comparisons) had a reduced integrity-closeness in pars orbitalis and insula, suggesting that the relationship between these areas and other brain regions is increased in schizophrenia. No differences were found between the First Episode Psychosis and Schizophrenia groups. Since in schizophrenia the brain is affected as a whole, this may mirror that these regions may be related to the generalized structural alteration seen in schizophrenia.

Background: Persistent postconcussion syndrome (PCS) occurs in around 5– 10% of individuals after mild traumatic brain injury (mTBI), but research into the underlying biology of these ongoing symptoms is limited and inconsistent. One reason for this could be the heterogeneity inherent to mTBI, with individualized injury mechanisms and psychological factors. A multimodal imaging study may be able to characterize the injury better. Aim: To look at the relationship between functional (fMRI), structural (diffusion tensor imaging), and metabolic (magnetic resonance spectroscopy) data in the same participants in the long term (>1 year) after injury. It was hypothesized that only those mTBI participants with persistent PCS would show functional changes, and that these changes would be related to reduced structural integrity and altered metabolite concentrations. Methods: Functional changes associated with persistent PCS after mTBI (>1 year postinjury) were investigated in participants with and without PCS (both n = 8) and non-head injured participants (n = 9) during performance of working memory and attention/processing speed tasks. Correlation analyses were performed to look at the relationship between the functional data and structural and metabolic alterations in the same participants. Results: There were no behavioral differences between the groups, but participants with greater PCS symptoms exhibited greater activation in attention-related areas (anterior cingulate), along with reduced activation in temporal, default mode network, and working memory areas (left prefrontal) as cognitive load was increased from the easiest to the most difficult task. Functional changes in these areas correlated with reduced structural integrity in corpus callosum and anterior white matter, and reduced creatine concentration in right dorsolateral prefrontal cortex. Conclusion: These data suggest that the top-down attentional regulation and deactivation of task-irrelevant areas may be compensating for the reduction in working memory capacity and variation in white matter transmission caused by the structural and metabolic changes after injury. This may in turn be contributing to secondary PCS symptoms such as fatigue and headache. Further research is required using multimodal data to investigate the mechanisms of injury after mTBI, but also to aid individualized diagnosis and prognosis.

Background: The investigation of neurodevelopment during late childhood and pre-adolescence has recently attracted a great deal of interest in the field of neuroimaging. One promising topic in this field is the formation of brain networks in healthy subjects. The integration between neural modules characterizes the ability of the network to process information globally. Although many fMRI-based neurodevelopment studies can be found in the literature, the analyses of very large samples (on the order of hundreds of subjects) that focus on the late childhood/pre-adolescence period and resting state fMRI are scarce, and most studies have focused solely on North American and European populations. Aims: In this study, we present a descriptive investigation of the developmental formation of the Default Mode Network and the Control Network based on a Brazilian, cross-sectional community sample of 447 typically developing subjects aged 7e15 years old. Methods: Resting state fMRI data were acquired using two MRI systems from the same manufacturer using the same acquisition parameters. We estimated the age effects on the strength of the links (between brain regions) and the network features (graph descriptors: degree and eigenvector centrality). Results: Our findings showed an increase in the antero-posterior connectivity in both studied networks during brain development. The graph analyses showed an increase in centrality with age for most regions in the Default Mode Network and the dorsal anterior and posterior cingulate, the right anterior insula and the left posterior temporal cortex in the Control Network. Conclusion: We conclude that the period of 7e15 years of age is crucial for the development of both the Default Mode and Control networks, with integration between the posterior and anterior neuronal modules and an increase in the centrality measures of the hub regions.

To assess the reproducibility of brain-activation and eye-movement patterns in a saccade paradigm when comparing subjects, tasks, and magnetic resonance (MR) systems.Forty-five healthy adults at two different sites (n = 45) performed saccade tasks with varying levels of target predictability: predictable (PRED), position predictable (pPRED), time predictable (tPRED), and prosaccade (SAC). Eye-movement pattern was tested with a repeated-measures analysis of variance. Activation maps reproducibility were estimated with the cluster overlap Jaccard index and signal variance coefficient of determination for within-subjects test-retest data, and for between-subjects data from the same and different sites.In all groups latencies increased with decreasing target predictability: PREDpPREDtPREDSAC (P0,001). Activation overlap was good to fair (0.40) in all tasks in the within-subjects test-retest comparisons and poor (0.40) in the tPRED for different subjects. The overlap of the different tasks for within-groups data was higher (0.40-0.68) than for the between-groups data (0.30-0.50). Activation consistency was 60-85% in the same subjects, 50-79% in different subjects, and 50-80% in different sites. In SAC, the activation found in the same and in different subjects was more consistent than in other tasks (50-80%).The predictive saccade tasks produced evidence for brain-activation and eye-movement reproducibility.

Autism spectrum disorders (ASD) are a group of conditions that show abnormalities in the neuroanatomy of multiple brain regions. The variability in the development of intelligence and language among individuals on the autism spectrum has long been acknowledged, but it remains unknown whether these differences impact on the neuropathology of ASD. In this study, we aimed to compare associations between surface-based regional brain measures and general intelligence (IQ) scores in ASD individuals with and without a history of language delay. We included 64 ASD adults of normal intelligence (37 without a history of language delay and 27 with a history of language delay and 80 neurotypicals). Regions with a significant association between verbal and nonverbal IQ and measures of cortical thickness (CT), surface area, and cortical volume were first identified in the combined sample of individuals with ASD and controls. Thicker dorsal frontal and temporal cortices, and thinner lateral orbital frontal and parieto-occipital cortices were associated with greater and lower verbal IQ scores, respectively. Correlations between cortical volume and verbal IQ were observed in similar regions as revealed by the CT analysis. A significant difference between ASD individuals with and without a history of language delay in the association between CT and verbal IQ was evident in the parieto-occipital region. These results indicate that ASD subgroups defined on the basis of differential language trajectories in childhood can have different associations between verbal IQ and brain measures in adulthood despite achieving similar levels of cognitive performance.