Search

The incidence of celiac disease in first-degree relatives of affected individuals is higher than in the general population, yet the clinical characteristics of this unique subset of patients has not been well described. Through a retrospective review of patients seen in a tertiary care pediatric celiac disease clinic, we identified 49 patients diagnosed with celiac disease following screening due to an affected first-degree relative. Although 51% of patients screened due to an affected first-degree relative were asymptomatic, their disease histology was as severe as those screened for symptoms suggestive of celiac disease. These findings support current recommendations to screen all first-degree relatives of patients with celiac disease regardless of clinical symptoms.

Decompression sickness (DCS) develops due to inert gas bubble formation in bodily tissues and in the circulation, leading to a wide range of potentially serious clinical manifestations. Its pathophysiology remains incompletely understood. In this study, we aim to explore changes in the human leukocyte transcriptome in divers with DCS compared to closely matched unaffected controls after uneventful diving. Cases (n = 7) were divers developing the typical cutis marmorata rash after diving with a confirmed clinical diagnosis of DCS. Controls (n = 6) were healthy divers who surfaced from a 25 msw dive without decompression violation or evidence of DCS. Blood was sampled at two separate time points—within 8 h of dive completion and 40–44 h later. Transcriptome analysis by RNA-Sequencing followed by bioinformatic analysis was carried out to identify differentially expressed genes and relate their function to biological pathways. In DCS cases, we identified enrichment of transcripts involved in acute inflammation, activation of innate immunity and free radical scavenging pathways, with specific upregulation of transcripts related to neutrophil function and degranulation. DCS-induced transcriptomic events were reversed at the second time point following exposure to hyperbaric oxygen. The observed changes are consistent with findings from animal models of DCS and highlight a continuum between the responses elicited by uneventful diving and diving complicated by DCS. This study sheds light on the inflammatory pathophysiology of DCS and the associated immune response. Such data may potentially be valuable in the search for novel treatments targeting this disease., peer-reviewed

The case of a diver with a history of decompression sickness (DCS) after recreational scuba diving is presented. Cutis marmorata, a subtype of cutaneous DCS, has been consistently associated with the presence of a persistent (patent) foramen ovale (PFO) as a risk factor. Diagnostic uncertainty arose when transthoracic echocardiography with antecubital injection of agitated saline bubbles (ASBs) did not show any significant shunt, but the presence of a large Eustachian valve was counteracted by intra-femoral injection of ASBs, showing a large PFO with spontaneous shunting. The importance of proper echocardiography techniques prior to resorting to intra-femoral injection of ASBs to counteract the haemodynamic effects of the Eustachian valve is emphasised.

Research on Liquefied Petroleum Gas (LPG) use for automotive application is stemmed from the lower cost of the fuel and also from its lower emission potential. This paper details the experimental implementation of LPG fuel onto a Peugeot four cylinder common rail diesel engine. This diesel engine was already electronically controlled with an in-house Engine Control Unit (ECU) already reported in earlier IEEE papers. The electronic and software implementation performed to achieve Dual Fuel operation is detailed, i.e. LPG addition in gaseous state in the inlet manifold in conjunction with Diesel Injection directly into the cylinder. The Diesel Injection is used as the ignition source and thus is required throughout the engine operation, i.e. from idle to full load. LPG addition was utilized from 20% load upwards. The experimental setup used the Diesel ECU already reported and made use of additional electronic circuitry and LabVIEW to control the low impedance LPG injectors. The additional electronic circuitry and LabVIEW control are therefore the main contribution presented in this paper.

Objective Clarifying the discrepancy between frequently high oxalate concentrations present in saliva, but negligible amounts of calcium oxalate deposits found on oral surfaces. Methods Studying the calcium oxalate concentration range that can lead to heterogeneous crystallization in the oral cavity. a) Minimum: calcium oxalate monohydrate (COM) seed crystals were pre-grown ([Ca2+] = [C2O42−] = 1 mM, 30 min, 37 °C), and then re-immersed for ≥6 h to find the solubility equilibrium concentration (no growth, no dissolution). The concentrations tested were [Ca2+]/[C2O42−] : 0.055/0.050, 0.060/0.055, 0.070/0.065 and 0.080/0.075 mM. Supersaturations were calculated via the Debye-Huckel-theory and COM morphologies examined by scanning electron microscopy (SEM). b) Maximum (at the heterogeneous/homogeneous crystallization equilibrium): hydroxyapatite (HA) seed crystals were used to heterogeneously crystallize COM (37 °C, 24 h), using oxalate concentrations between 0.2 and 0.5 mM and calcium concentrations of 0.5 mM. COM-forming oxalate consumption was spectroscopically examined; COM precipitates were investigated by SEM; and HA identity was confirmed by X-ray analysis. Results Within the concentration range of [Ca2+]/[C2O42−]:0.060/0.055 mM (minimum) and [Ca2+]/[C2O42−]:0.50/0.25 mM (maximum) COM precipitates heterogeneously. In terms of mass, this corresponds to a range of 8.04–36.53 mg/l (daily) or an average of 14.32 mg COM (mimicking e.g. plaque mineralization). Higher concentrations react homogeneously (mimicking precipitation within saliva). Conclusion In vivo, only ∼0.05 % oxalate present in saliva reacts with oral surfaces daily, corresponding to ∼0.0665 μmol/l or ∼9.72 μg COM per day. Calcium-consuming calcium phosphate formation and phosphoproteins such as statherin obviously hinder intraoral COM formation.

Hyperbaric medicine is a relatively young specialty that remains in the blind spot of most doctors’ awareness. This study endeavors to identify the level of awareness of the indications for hyperbaric oxygen (HBO2) therapy among a doctor population in a developed country and factors which may improve referral rates. An anonymized questionnaire was distributed to doctors licensed to practice in Malta. Questions included physician specialty, demographics and previous exposure to diving and/or hyperbaric medicine. Moreover, two scoring systems were used to score subjects on HBO2-related topics. Binomial logistic regression models and generalized linear models were used in the statistical analysis. A total of 152 full replies were obtained and analyzed. Respondents who had visited a hyperbaric unit (HBU) (p=0.002) or attended a lecture on HBO2 (p=0.006) scored better than their counterparts, indicating better awareness of HBO2 indications and local chamber location. A previous HBU visit (p=0.001), being a hospital-based doctor (p=0.027) and a history of scuba diving (p=0.03) were associated with willingness to refer patients for HBO2 in the future. Encouraging visits to an HBU has been shown to be associated with multiple factors, which are expected to result in improved referral rates. Targeted educational sessions to doctors and medical students are likely to be beneficial in improving correct referral of patients for HBO2. The findings from this study may prove useful in improving appropriate referral rates of patients who may benefit from this useful treatment modality.

The performance of the Hot Gas Test Stand was further improved by electronically controlling the compressor flow using an Electronic Throttle Body (ETB). Control of the ETB was done at two different levels: a PID controller on an Arduino UNO was used to control the PWM required to open the throttle to the commanded angle; and a LabViewPid controller to calculate the required ETB angle for the set point air flow rate. For better control of the throttle plate movement, the control time of the microcontroller Arduino UNO board was reduced to 20 ms. On the other level, in LabVIEW, two control systems configurations were studied, ‘PID Only control’ and ‘PID with Feedforward control’. It was found that linking the turbine flow rate to the compressor flow rate made the test stand perform much better and easier to control. This is understandable as the turbine mass flow in an engine is always approximately equal to the mass flow of air coming in.

This paper details how it is possible to extract sensor data from a vehicle's CAN bus without OEM support. Experiments were done using a production Toyota GT86 (production year 2016). This vehicle is equipped with a range of sensors connected to multiple Electronic Control Units (ECU) namely those for the Antilock Braking System (ABS), the Air Bag system and the engine. These ECU's utilize the sensor data for their control strategy but the information is also available on request through OnBoard Diagnostic (OBD) socket. A campaign was then implemented to request all pertinent data from the OBD whilst driving and also ‘listen’ to all CAN messages over the bus. The desired sensor data from OBD was then linked to the relevant CAN messages that were communicating the same sensor information. Hence through this laborious data matching exercise a list of sensor data became available directly from the bus just by listening and also with the added advantage that is was available at much faster rates than could possibly be achieved by question and reply from OBD. Additional Inertial Measurement Units (IMU) were implemented at the centre, front and rear of the vehicle. Steady state experiments were done by driving around constant radius circles at various speeds, i.e. skid pad tests. The data from the IMU's and CAN bus data were successfully used to plot curves of steering angle versus lateral acceleration and also slip angle versus lateral acceleration for three different tire types and different tire pressures. Transient tests were performed by driving the vehicle on a race track using two different sets of tires. Data acquired on the race track included longitudinal and lateral accelerations, engine speed, gear change and braking.

Introduction Scuba diving is a big part of the tourism sector in Malta, and all the cases of decompression illness (DCI)are treated within the single hyperbaric referral centre in the country. Methods This retrospective analysis reviews all the medical records of divers with DCI in Malta within the 30-year period between 1987 to 2017 who required recompression therapy with hyperbaric oxygen. Results There were 437 discrete cases of DCI managed with recompression therapy. Amongst DCI subtypes, the prevalence of musculo-skeletal DCI is decreasing, whereas that of vestibulo-cochlear DCI is increasing. Conclusion The increasing prevalence of vestibulo-cochlear DCI may be due to a change in diving practices in Malta.

[This corrects the article DOI: 10.1371/journal.pone.0210863.].

It has been suggested that perception without awareness can be demonstrated by a dissociation between performance in objective (forced-choice) and subjective (yes–no) tasks, and such dissociations have been reported both for simple stimuli and more complex ones including faces. However, signal detection theory (SDT) indicates that the subjective measures used to assess awareness in such studies can be affected by response bias, which could account for the observed dissociation, and this was confirmed by Balsdon and Azzopardi (2015) using simple visual targets. However, this finding may not apply to all types of stimulus, as the detectability of complex targets such as faces is known to be affected by their configuration as well as by their stimulus energy. We tested this with a comparison of forced-choice and yes–no detection of facial stimuli depicting happy or angry or fearful expressions using a backward masking paradigm, and using SDT methods including correcting for unequal variances in the underlying signal distributions, to measure sensitivity independently of response criterion in 12 normal observers. In 47 out 48 comparisons there was no significant difference between sensitivity ( d a ) in the two tasks: hence, across the range of expressions tested it appears that the configuration of complex stimuli does not enhance detectability independently of awareness. The results imply that, on the basis of psychophysical experiments in normal observers, there is no reason to postulate that performance and awareness are mediated by separate processes.

This paper details the experimental work performed on the verification of the dynamic kinematic performance of camshafts designed and fabricated for operation on a turbocharged Kawaski 600cc spark ignition engine. The engine can operate to 12500rpm and the camshafts were shown to incur jump/bounce at speeds higher than 12500 rpm as designed. The Original Equipment Manufacturer OEM naturally aspirated 600cc engine was turbocharged for Formula SAE competition which gave the motivation to design bespoke camshafts suited for the introduction of the turbocharger in the flow stream. Cam valve timings and lobe profiles for the intake and exhaust valves were designed using Ricardo Wave and Valdyn. The purposely built test stand is detailed together with the sensing and data analysis performed for jump/bounce detection. A commercial knock sensor mounted on the cylinder head together with data analysis in LabView were used.

Diesel engines in both the automotive and industrial sectors are nowadays electronically controlled. Electronic control provides accurate real time processing of the relevant sensory data on which fuelling is determined. Fuel economy as well as emissions are very dependent on the diesel fuel quantity, timing and injection pressure, which in turn determines the shape of the injection rate diagram, the spray distribution and the fuel droplet size. NO x is also known to be very dependent on flame temperature which can be controlled by the quantity of Exhaust Gas Recirculation (EGR). Research on the real time control of a common rail diesel engine was undertaken at the University of Malta. A Peugeot 2.0HDi common rail engine was controlled with a custom made electronic Engine Control Unit (ECU). A control strategy for the diesel rail pressure was developed that is based on simple 2D look up tables rather than more complex 3D maps. This allowed the ECU Graphical User Interface (GUI) and ECU firmware to be very similar to the gasoline (petrol) version of the ECU. The successfully developed fuel rail pressure scheme based on RPM, Mass Air Flow and Torque Requirement is given in this paper. Furthermore the values found experimentally for the speed-density control of the engines are also given. Top Dead Center (TDC) determination based on in-cylinder pressure measurements was conducted to better calculate the Start of Injection (SOI) and Indicated Mean effective Pressure (IMEP).

BACKGROUND: Although the hepatitis B vaccination has an efficacy of 95%, the CDC reports that 275 million people are infected with chronic hepatitis B, with 700,000 deaths per year. In Ontario, a publicly-funded, 2-dose vaccine series is routinely offered to grade 7 students. However, the vertical transmission of hepatitis B is a risk for infants born to carrier mothers. Therefore, prospective mothers are routinely screened for HBsAg during the first trimester of pregnancy. The Canadian Immunization Guide recommends that all infants born to infected mothers should receive vaccine and hepatitis B immune globulin (HBIg) within 12 hours of birth. As there is no published literature on the timeliness of hepatitis B immunization, this study aimed to investigate time of HBIg and vaccine administration in infants born to HBsAg positive mothers. OBJECTIVES: The primary outcome was the proportion of infants receiving HBIg and Hepatitis B vaccine within 12 hours of birth. DESIGN/METHODS: Mother-infant dyads were identified where the hepatitis B vaccine was ordered. Full review was conducted for infants born to HBsAg positive mothers between 2010 and 2015. Mother and infant charts were paired and retrospectively reviewed across 6 hospital sites in Ontario, including 2 community hospitals, 2 academic hospitals, and 2 satellite teaching hospitals. Between-group differences were tested through Welch’s analysis of variance and associations were explored through Spearman’s rank correlation. Statistical significance was set for P

Biological aging is associated with progressive damage accumulation, loss of organ reserves, and systemic inflammation ('inflammaging'), which predispose for a wide spectrum of chronic diseases, including several types of cancer. In contrast, aerobic exercise training (AET) reduces inflammation, lowers all-cause mortality, and enhances both health and lifespan. In this study, we examined the benefits of early-onset, lifelong AET on predictors of health, inflammation, and cancer incidence in a naturally aging mouse model (C57BL/J6). Lifelong, voluntary wheel-running (O-AET; 26-month-old) prevented age-related declines in aerobic fitness and motor coordination vs. age-matched, sedentary controls (O-SED). AET also provided partial protection against sarcopenia, dynapenia, testicular atrophy, and overall organ pathology, hence augmenting the 'physiologic reserve' of lifelong runners. Systemic inflammation, as evidenced by a chronic elevation in 17 of 18 pro- and anti-inflammatory cytokines and chemokines (P < 0.05 O-SED vs. 2-month-old Y-CON), was potently mitigated by lifelong AET (P < 0.05 O-AET vs. O-SED), including master regulators of the cytokine cascade and cancer progression (IL-1β, TNF-α, and IL-6). In addition, circulating SPARC, previously known to be upregulated in metabolic disease, was elevated in old, sedentary mice, but was normalized to young control levels in lifelong runners. Remarkably, malignant tumours were also completely absent in the O-AET group, whereas they were present in the brain (pituitary), liver, spleen, and intestines of sedentary mice. Collectively, our results indicate that early-onset, lifelong running dampens inflammaging, protects against multiple cancer types, and extends healthspan of naturally-aged mice.

The retinal fovea, which corresponds to the central degree or so of vision, is spatially over-represented in the visual cortex. It is about 0.01% of retina area, but at least 8% of the striate cortex. Does this simply reflect an equivalently uneven distribution of ganglion cells in the retina, or is the cortical representation of the fovea preferentially expanded? The answer hinges on the resolution of long-standing discrepancies between the retinal and cortical magnification factors. We approached the problem in a different way, using a retrograde transneuronal tracer from cortex to retina to relate directly the number of ganglion cells projecting to marked areas of striate cortex. We report here that ganglion cells near the fovea were allocated 3.3 to 5.9 times more cortical tissue than more peripheral ones, and conclude that the cortical representation of the most central retina is much greater than expected from the density of its ganglion cells.

The ability of a human observer to detect the presence of a briefly flashed picture of a face can depend on the picture's spatial configuration, that is on whether its features are rearranged (jumbled) or are in their normal configuration. The face-detection effect (FDE) is found under conditions of backward masking, when the presence of a face can be detected with shorter masking intervals when it is in the normal than when in the rearranged configuration. A similar effect is found when the subject is asked to classify the face as rearranged or not - the face-classification effect (FCE). Part of the interest of the FDE and the FCE is that they show how the configuration of a stimulus can be an important factor in the perceptual processing which leads to detection and classification of the stimulus. To analyse these effects we recorded from single neurons in the cortex in the superior temporal sulcus of macaques when they were shown (in a visual fixation task) normal and rearranged faces under backward masking conditions shown in experiments 2 and 3 to produce, with the same apparatus, the FCE, and also to produce comparable effects on the identification of which face was present (called hereafter the face-identification effect), and also of the clarity of the face. We found in experiment 1 that there are some face-selective neurons which respond to faces only, or better, when the features in the faces are in their normal configuration rather than rearranged. We also showed in this experiment that the difference in the response to the normal as compared to the rearranged faces became greater when the masking stimulus was delayed more. Thus, at intermediate delays, there are more neurons active for the normal than for the rearranged face. We therefore propose that the FDE, the FCE, and the face-identification effect arise because the total number of neurons activated by faces in their normal configuration is greater than that activated by rearranged faces, because of the sensitivity of some face-selective neurons to the spatial arrangement of the features. The experiments also show that backward visual masking does produce abrupt termination of the firing of neurons in the temporal cortical visual system, so that the duration of a neuronal response is very short when visual stimuli can just be perceived.

The derivation of a reliable, subjective measure of awareness that is not contaminated by observers' response bias is a problem that has long occupied researchers. Kunimoto et al. (2001) proposed a measure of awareness (a′) which apparently meets this criterion: a′ is derived from confidence ratings and is based on the intuition that confidence should reflect awareness. The aim of this paper is to explore the validity of this measure. Some calculations suggested that, contrary to Kunimoto et al.'s intention, a′ can vary as a result of changes in response bias affecting the relative proportions of high- and low-confidence responses. This was not evident in the results of Kunimoto et al.'s original experiments because their method may have artificially 'clamped' observers' response bias close to zero. A predicted consequence of allowing response bias to vary freely is that it can result in a′ varying from negative, through zero, to positive values, for a given value of discriminability (d′). We tested whether such variations are likely to occur in practice by employing Kunimoto et al.'s paradigm with various modifications, notably the removal of constraints upon the proportions of low- and high-confidence responses, in a visual discrimination task. As predicted, a′ varied with response bias in all participants. Similar results were found when a′ was calculated from pre-existing data obtained from a patient with blindsight: a′ varied through a range of positive results without approaching zero, which is inconsistent with his well-documented lack of awareness. A second experiment showed how response bias could be manipulated to yield elevated values of a′. On the basis of these findings we conclude that Kunimoto's measure is not as impervious to response bias as was originally assumed.

Cortical area, MT (middle temporal area) is specialized for the visual analysis of stimulus motion in the brain. It has been suggested [Brain 118 (1995) 1375] that motion signals reach area MT via two dissociable routes, namely a ‘direct’ route which bypasses primary visual cortex (area, striate cortex (V1)) and is specialized for processing ‘fast’ motion (defined as faster than 6 ◦ /s) with a relatively short latency, and an ‘indirect’ route via area V1 for processing ‘slow’ motion (slower than 6 ◦ /s) with a relatively long latency. We tested this proposal by measuring the effects of unilateral V1 lesions on the magnitudes and latencies of responses to fast- and slow-motion (depicted by random dot kinematograms (RDK) ) of single neurons in areas MT and medial superior temporal area (MST) of anaesthetized macaque monkeys. In the unlesioned hemisphere contralateral to a V1 lesion, response magnitudes and latencies of MT neurons were similar to those previously reported from MT neurons in normal monkeys, and there was no significant association between slow movement and long response latency (>100 ms), or between fast movement and short latency (≤100 ms). V1 lesions led to diminished response magnitudes and increased latencies in area MT of the lesioned hemisphere, but did not selectively abolish MT responses to slow moving stimuli, or abolish long-latency responses to either slow- or fast-moving stimuli. Response magnitudes and latencies in area MST, which receives visual inputs directly from area MT and is also specialized for visual analysis of motion, were unaffected by V1 lesions (though we have shown elsewhere that directionally-selective responses in both areas were impaired by V1 lesions). Overall, the results are incompatible with the hypothesis that there are dissociable routes to MT specialized for processing separately fast and slow motion. © 2003 Published by Elsevier Ltd.

Motion detection is typically spared in blindsight, which results from damage to the striate cortex (area V1) of the brain that is sufficient to eliminate conscious visual awareness and severely reduce sensitivity to luminance contrast, especially for high spatial and low temporal frequencies. Here we show that the discrimination of motion direction within cortically blind fields is not attributable to feature tracking (the detection of changes in position or shape), but is due instead to the detection of first-order motion energy (spatiotemporal changes in luminance). The key to this finding was a version of the line motion illusion entailing reverse-phi motion in which opposing motion directions are simultaneously cued by motion energy and changes in stimulus shape. In forced-choice tests, a blindsighted test subject selected the direction cued by shape change when the stimulus was presented in his intact field, but reliably selected the direction cued by motion energy when the same stimulus was presented in his blind field, where relevant position information was either inaccessible or invalid. Motion energy has been characterized as objectless, so reliance on motion energy detection is consistent with impaired access to shape information in blindsight. The dissociation of motion direction by visual field (cortically blind vs. intact) provides evidence that two pathways from the retina to MT/V5 (the cortical area specialized for motion perception) are functionally distinct: the retinogeniculate pathway through V1 is specialized for feature-based motion perception, whereas the retinocollicular pathway, which bypasses V1, is specialized for detecting motion energy.

The concept of relative blindsight, referring to a difference in conscious awareness between conditions otherwise matched for performance, was introduced by Lau and Passingham (2006) as a way of identifying the neural correlates of consciousness (NCC) in fMRI experiments. By analogy, absolute blindsight refers to a difference between performance and awareness regardless of whether it is possible to match performance across conditions. Here, we address the question of whether relative and absolute blindsight in normal observers can be accounted for by response bias. In our replication of Lau and Passingham’s experiment, the relative blindsight effect was abolished when performance was assessed by means of a bias-free 2AFC task or when the criterion for awareness was varied. Furthermore, there was no evidence of either relative or absolute blindsight when both performance and awareness were assessed with bias-free measures derived from confidence ratings using signal detection theory. This suggests that both relative and absolute blindsight in normal observers amount to no more than variations in response bias in the assessment of performance and awareness. Consideration of the properties of psychometric functions reveals a number of ways in which relative and absolute blindsight could arise trivially and elucidates a basis for the distinction between Type 1 and Type 2 blindsight.

The larynx is an extremely rare site of involvement by lymphomatous disease.We present two cases of isolated laryngeal high-grade and another low-grade lymphoma, together with a literature review of laryngeal lymphoma management., peer-reviewed

Various residual visual capacities have been reported for the phenomenally blind field of hemispherectomized patients, providing evidence for the relative roles of cortical and subcortical pathways in vision. We attempted to characterize these functions by examining the ability of five patients to detect, localize, and discriminate high-contrast flashed, flickering and moving targets. Dependent measures were verbal, manual, and oculomotor responses. As a control for light scatter, intensity thresholds for monocular detection of targets in the hemianopic field were compared with thresholds obtained when using an additional half eyepatch to occlude the blind hemiretina of the tested eye. One unilaterally destriate patient was tested on the same tasks. In photopic conditions, none of the hemispherectomized patients could respond to visual cues in their impaired fields, whereas the destriate patient could detect, discriminate, and point to targets, and appreciate the apparent motion of stimuli across his midline. Under reduced lighting, the threshold luminance required by hemispherectomized patients to detect stimuli presented monocularly was similar to that required for their detection when all visual information was occluded in the blind field, and only available to the visual system indirectly via light scatter. In contrast, the destriate patient's monocular threshold in his blind field was substantially lower than that for stimuli directly occluded in the blind field. As we found no range of stimuli which the hemispherectomized patients could detect or discriminate that was not also associated with discriminable scattered light, we conclude that the subcortical pathways which survive hemispherectomy cannot mediate voluntary behavioural responses to visual information in the hemianopic field.

1. The responses of single neurons in the inferior temporal cortex and the cortex in the banks of the anterior part of the superior temporal sulcus of three awake, behaving macaques were recorded during a visual fixation task. Stimulus images subtending 17 or 8.5 degrees were presented in the center of the display area, and fixation was either at the center of the display area, or at one of four positions that were on the stimulus, or several degrees off the edge of the test stimulus. The experiments were performed with face-selective cells, and the responses were compared for fixation at each position for both effective and noneffective face stimuli for each cell. 2. The firing rates of most neurons to an effective image did not significantly alter when visual fixation was as far eccentric as the edge of the face, and they showed only a small reduction when the fixation point was up to 4 degrees from the edge of the face. Moreover, stimulus selectivity across faces was maintained throughout this region of the visual field. 3. The centers of the receptive fields of the cells, as shown by the calculated "centers of gravity," were close to the fovea, with almost all being within 3 degrees of the fovea. 4. The receptive fields of the cells typically crossed the vertical midline for at least 5 degrees. 5. Information theory procedures were used to analyze the spike trains of the visual neurons. Nearly six times more information was carried by these neurons' firing rate about the identity of an image than about its position in the visual field. Thus the information theory analysis showed that the responses of these neurons reflected information about which stimulus had been seen in a relatively translation invariant way. 6. Principal component analysis showed that principal component 1 (PC1) is related primarily to firing rate and reflected information primarily about stimulus identity. (For identity PC2 added only 14% more information to that contained in PC1.) Principal component 2 (PC2) was more closely related to neuronal response latencies, which increased with increasing eccentricity of the image in the visual field. PC2 reflected information about the position of the stimulus in the visual field, in that PC2 added 109% more information to that contained in PC1 about the position of the stimulus in the visual field.(ABSTRACT TRUNCATED AT 400 WORDS)

In vitro studies have shown that the phosphoprotein osteopontin (OPN) inhibits the nucleation and growth of hydroxyapatite (HA) and other biominerals. In vivo, OPN is believed to prevent the calcification of soft tissues. However, the nature of the interaction between OPN and HA is not understood. In the computational part of the present study, we used molecular dynamics simulations to predict the adsorption of 19 peptides, each 16 amino acids long and collectively covering the entire sequence of OPN, to the {100} face of HA. This analysis showed that there is an inverse relationship between predicted strength of adsorption and peptide isoelectric point (P

Some patients with brain damage affecting the striate cortex, though clinically blind in their field defects, can still discriminate visual stimuli when forced choice procedures are used. Such patients seem particularly sensitive to moving stimuli in their scotomata, though there are conflicting reports as to whether they can discriminate the direction of motion. We tested three patients with areas of cortical blindness for their ability to detect and discriminate the direction of motion of a variety of first-order motion stimuli, namely bars, gratings, plaids and random dot kinematograms depicting translation and motion in depth, during forced choice tasks. The patients could detect the presence of movement in any kind of stimulus, and could discriminate the direction of single bars, but none could discriminate the direction of motion of the more complex stimuli (gratings, plaids and random dot kinematograms) or discriminate between 0 and 100% coherent random dot kinematograms at any speed tested (from 4 to 64 degrees /s). Similar results were obtained from one of the patients who was additionally tested with second-order versions of the translated bar and random dot kinematograms, eliminating light scatter as an explanation. Overall, the results suggest that motion processing in the scotoma is severely impaired, and that the puzzling discrepancies between previous studies can be accounted for by the type of stimulus used. The motion discrimination impairment caused by brain damage affecting the primary visual cortex is inconsistent with the proposed existence of a subcortical pathway to extrastriate cortical motion areas (such as areas MT and MST) which bypasses the striate cortex and is specialized for analysing 'fast' motion.

Central vision is substantially over represented in the lateral geniculate nucleus (dLGN) and striate cortex. The over representation could be accompanied by a selective expansion of central vision in parvocellular dLGN, in which case the ratio of parvocellular to magnocellular inputs to striate cortex should change with retinal eccentricity. To test this, sample ratios were determined from counts of neurons in dLGN labelled retrogradely with WGA-HRP from striate cortex at the cortical representations of various eccentricities. Parvocellular to magnocellular ratios decreased from a mean of 35:1 at the fovea to 5:1 at 15 degrees eccentricity. Furthermore, they exceeded the ratio of P beta to P alpha ganglion cells in central retina, but not in peripheral retina, showing that the uneven P to M ratio in the LGN does not merely mirror the distribution of ganglion cells in the retina. This provides direct evidence for selective over representation of central vision in parvocellular dLGN.

Some patients with damaged striate cortex have blindsight-the ability to discriminate unseen stimuli in their clinically blind visual field defects when forced-choice procedures are used. Blindsight implies a sharp dissociation between visual performance and visual awareness, but signal detection theory indicates that it might be indistinguishable from the behavior of normal subjects near the lower limit of conscious vision, where the dissociations could arise trivially from using different response criteria during clinical and forced-choice tests. We tested the latter possibility with a hemianopic subject during yes-no and forced-choice detection of static and moving targets. His response criterion differed significantly between yes-no and forced-choice responding, and the difference was sufficient to produce a blindsight-like dissociation with bias-sensitive measures of performance. When measured independently of bias, his sensitivity to static targets was greater in the forced-choice than in the yes-no task (unlike normal control subjects), but his sensitivity to moving targets did not differ. Differences in response criterion could therefore account for dissociations between yes-no and forced-choice detection of motion, but not of static pattern. The results explain why patients with blindsight are apparently more often "aware" of moving stimuli than of static stimuli. However, they also imply that blindsight is unlike normal vision near threshold, and that pattern- and motion-detection in blindsight may depend on different sets of neural mechanisms during yes-no and forced-choice tests.

Blindsight is the rare and paradoxical ability of some human subjects with occipital lobe brain damage to discriminate unseen stimuli in their clinically blind field defects when forced-choice procedures are used, implying that lesions of striate cortex produce a sharp dissociation between visual performance and visual awareness. Skeptics have argued that this is no different from the behavior of normal subjects at the lower limits of conscious vision, at which such dissociations could arise trivially by using different response criteria during clinical and forced-choice tests. We tested this claim explicitly by measuring the sensitivity of a hemianopic patient independently of his response criterion in yes-no and forced-choice detection tasks with the same stimulus and found that, unlike normal controls, his sensitivity was significantly higher during the forced-choice task. Thus, the dissociation by which blindsight is defined is not simply due to a difference in the patients’ response bias between the two paradigms. This result implies that blindsight is unlike normal, near-threshold vision and that information about the stimulus is processed in blindsighted patients in an unusual way.

The central part of the retina, which includes the fovea, is substantially overrepresented in the topographic map of the retina in the striate cortex. We tested whether this simply reflects the uneven distribution of ganglion cells in the retina in accordance with the “principle” of peripheral scaling, or whether there is additional expansion of the fovea and adjacent retina in the retinocortical projection. Wheatgerm agglutinated horseradish peroxidase was injected into the striate cortex of three rhesus macaque monkeys so as to surround the representation of the fovea at a mean eccentricity of 8.6°, and the retinae were processed histochemically to stain the retrogradely and transneuronally labelled ganglion cells which projected topographically to the injection sites. This enabled regions of the striate cortex to be related precisely to corresponding regions of the dorsal lateral geniculate nucleus and retina. Mathematical models of the distribution of ganglion cells in the retina, clipped, three-dimensional computer reconstructions of the striate cortex and lateral geniculate nucleus, and counts of neurons in the latter, were used to calculate the proportion of neurons allocated to the marked perifoveal region at each stage of projection. This was used to calculate the relative allocation of neurons to the representation of the fovea and surrounding retina among the different stages of the visual pathway. The values obtained showed that the cortical representation of the perifovea was expanded two to three times more than could be accounted for on the basis of ganglion cell topography in the retina, and that the expansion occurred both between the retina and the thalamus, and between the thalamus and the cortex. These results are inconsistent with the idea that peripheral scaling is a general principle of sensory representation in the cortex. They could also explain why many visual thresholds, including hyperacuities, cannot be accounted for by peripheral factors such as ganglion cell density.

We devised mathematical models of the topography of ganglion cells in the retina of macaque monkeys. The models consisted of a sum-of-three exponentials function fitted to measurements of ganglion cell density made on the nasal horizontal meridian, combined with known anisotropies across the horizontal and vertical meridians by means of elliptic interpolation to provide a full description of their density across the whole of the retinal surface. Integration using standard numerical techniques allowed the number of ganglion cells in arbitrary regions of the retina to be estimated. The topography of actual and effective total ganglion cell populations, and of primate alpha and gamma retinal ganglion cells, was modelled on previously published data. The models were used to test the hypothesis that the retinal projection to the striate cortex in macaque monkeys is peripherally scaled (i.e. merely reflects the eccentricity-dependent variation in density of ganglion cells in the retina) by comparing the cumulative proportion of ganglion cells with the cumulative proportion of cortical area as a function of eccentricity in the visual field. Discrepancies between the two curves indicated that the fovea and immediately surrounding retina are overrepresented in the striate cortex (i.e. there is more cortex per ganglion cell in and near the fovea than in the periphery), and the fact that the discrepancies persisted out to 25-50 degrees of eccentricity showed that the overrepresentation cannot be explained by the lateral displacement of foveal ganglion cells.

Four patients with functional hemispherectomy, one patient with a complete anatomical hemispherectomy, and one patient with unilateral removal of the temporal, parietal and occipital lobes took part in two sets of experiments designed to investigate their residual sensitivity to motion-in-depth in the hemianopic visual field. Two types of computer-generated visual displays were used; in the first set of experiments, a dot pattern and in the second, a circular checkerboard. These simulated either convergent, divergent or reversed rotational motion. Each set of experiments consisted of two parts; in the first part, electrodermal responses were monitored during stimulus presentation while the subjects performed a simple distracting task. In the second part, subjects were asked to state verbally the direction of stimulus motion. Contrary to expectations, no reliable changes in skin conductance were elicited from any of the subjects by changes in the direction of motion of the component parts of either the dot pattern display or the circular checkerboard display. Furthermore, none of the subjects were able to discriminate the direction of motion of the target patterns when presented in the hemianopic field. The most parsimonious explanation is that the subcortical visual pathways which survive hemispherectomy are unable to process visual information relating to motion in depth.

We placed pellets of horseradish peroxidase in the superior colliculus of four macaque monkeys and retrogradely labelled the retinal ganglion cells of both eyes. The ratio of labelled cells in the contralateral nasal retina and the ipsilateral temporal retina was no different from the ratio found after implants in the optic nerve, which label the entire afferent pathway. Our finding therefore invalidates the proposal that prominent differences in the properties of “blindsight” in monocular nasal and temporal visual fields arise from differences in the projection from the nasal and temporal retina to the midbrain. We also measured the size of the soma and dendritic field of the labelled ganglion cells (mostly gamma cells) and compared them with those of alpha and beta cells that project to the dorsal lateral geniculate nucleus. Soma size was very close to that of beta cells at all eccentricities but was much smaller than that of alpha cells. Dendritic field size was significantly larger than that of beta cells but was smaller than that of alpha cells. The number of primary dendrites was counted for cells labelled from the midbrain and in samples of alpha and beta cells labelled from the optic nerve. At eccentricities of 3–7 mm there was a consistent and prominent difference between beta and gamma cells. The results show that at intermediate eccentricities even ganglion cells whose distal dendrites are too poorly labelled to reveal their morphological class can never the less be categorized as alpha, beta or gamma by using a combination of soma size and number of primary dendrites. This is particularly useful when attempting to classify retinal ganglion cells following microinjections into selected target nuclei of optic axons.

Multiple random quadrats (25cm by 25cm) were sampled at five sites on depositing shores in South Wales and the Isle of Man. The effect of increased number of samples was examined in relation to the reliability of estimation of various ecological measures - J, H', number of species, total individuals, total individuals of selected species. The replication required varies with the measure involved, but generally 10–20 or even more quadrats are needed for reliable information which can be used to detect other than very gross changes with time. In monitoring programmes it is thus advantageous to concentrate sampling effort on a limited number of sites with high replication because of this considerable spatial variation. The need to define specific aims, and to design a sampling format related to these aims, is emphasized.