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The functional meaning and neural basis of the P3b component of ERPs are still under debate. One of the main issues is whether P3b reflects only stimulus-related processes (stimulus evaluation hypothesis) or response-related processes as well (stimulus-response or S-R link activation hypothesis). Here, we conducted an EEG experiment examining whether P3b may indeed reflect an S-R link activation, followed by an fMRI experiment in which we explored the brain areas and functional connectivity possibly constituting the neural basis of these sensorimotor links. In both experiments, two successive visual stimuli, S1 and S2, were presented with a 1 sec interval, and responses were defined either by S1 or S2, while participants responded only after S2 onset. The obtained EEG results suggest that P3b may be interpreted in terms of the S-R link activation account, although further studies are needed to disentangle P3-related activity from overlapping anticipatory activity. The obtained fMRI results showed that processing of the relevant S1 involved activation of a distributed postero-anterior sensorimotor network, and increased strength of functional connectivity within this network. This network may underlie activation of the S-R links, thus possibly also the P3b component, forming a bridging step between sensory encoding and response execution., SCOPUS: ar.j, info:eu-repo/semantics/published

The human brain is able to consider that two sensory stimuli are synchronous while they activate the cortex with some delay because they follow different neurological pathways. This process is only possible if the time interval between the two stimuli does not exceed a certain limit, called "Temporal Binding Window" (TBW). Studies of this parameter, involving the vestibular perception, are difficult because subjects must be moved, which generates parasitic proprioceptive information. By cons, in patients equipped with a vestibular implant, it is possible to generate a vestibular perception selectively by electrical stimulation of the vestibular nerve. These patients are therefore an unique model to study the TBW between visual and vestibular perception.Le cerveau humain est capable de considérer que deux stimuli sensoriels sont synchrones alors qu’ils activent le cortex avec un décalage temporel dû au fait qu’ils suivent des voies neurologiques différentes. Ce processus n’est possible que si l’intervalle de temps entre les deux stimuli ne dépasse pas un certain délai, qu’on appelle « Temporal Binding Window » (TBW). Etudier ce paramètre en mettant en jeu la perception vestibulaire est difficile puisqu’il faut bouger le sujet et donc générer aussi des informations proprioceptives. Par contre, chez les patients porteurs d’un implant vestibulaire, il est possible de délivrer une perception vestibulaire de façon sélective par stimulation électrique du nerf vestibulaire. Ces patients représentent donc un modèle unique pour étudier le TBW entre les perceptions visuelle et vestibulaire.

We used functional magnetic resonance imaging to examine whether motivational-salient cues could exert a differential impact on proactive (the restrain of actions in preparation for stopping) and reactive (outright stopping) inhibition. Fourteen high-frequency poker players, and 14 matched non-gambler controls, performed a modified version of the stop-signal paradigm, which required participants to inhibit categorization of poker or neutral pictures. The probability that a stop-signal occurs (0%, 17%, 25%, 33%) was manipulated across blocks of trials, as indicated by the color of the computer screen. Behavioral analyses revealed that poker players were faster than controls in categorizing pictures across all levels of proactive motor response inhibition (go trials). Brain imaging analyses highlighted higher dorsal anterior cingulate cortex activation in poker players, as compared to controls, during reactive inhibition. These findings suggest that, due to their faster rates of stimulus discrimination, poker players might have recruited more cognitive resources than controls when required to stop their response (reactive inhibition). Nevertheless, no main effect of stimulus type was found, on either proactive or reactive inhibition. Additional studies are, therefore, needed in order to confirm that investigating the dynamics between reactive and proactive inhibition offers a discriminative analysis of inhibitory control toward motivational-salient cues., SCOPUS: ar.j, info:eu-repo/semantics/published

International audience; Visual processing has been extensively explored in deaf subjects in the context of verbal communication, through the assessment of speech reading and sign language abilities. However, little is known about visual emotional processing in adult progressive deafness, and after cochlear implantation. The goal of our study was thus to assess the influence of acquired post-lingual progressive deafness on the recognition of dynamic facial emotions that were selected to express canonical fear, happiness, sadness, and anger. A total of 23 adults with post-lingual deafness separated into two groups; those assessed either before (n = 10) and those assessed after (n = 13) cochlear implantation (CI); and 13 normal hearing (NH) individuals participated in the current study. Participants were asked to rate the expression of the four cardinal emotions, and to evaluate both their emotional valence (unpleasant-pleasant) and arousal potential (relaxing-stimulating). We found that patients with deafness were impaired in the recognition of sad faces, and that patients equipped with a CI were additionally impaired in the recognition of happiness and fear (but not anger). Relative to controls, all patients with deafness showed a deficit in perceiving arousal expressed in faces, while valence ratings remained unaffected. The current results show for the first time that acquired and progressive deafness is associated with a reduction of emotional sensitivity to visual stimuli. This negative impact of progressive deafness on the perception of dynamic facial cues for emotion recognition contrasts with the proficiency of deaf subjects with and without CIs in processing visual speech cues (Rouger et al., 2007; Strelnikov et al., 2009; Lazard and Giraud, 2017). Altogether these results suggest there to be a trade-off between the processing of linguistic and non-linguistic visual stimuli.

Two experiments were run to complete our understanding of the role of verbal and visuospatial encoding in the construction of a spatial model from visual input. In experiment 1 a dual task paradigm was applied to young adults who learned a route in a virtual environment and then performed a series of nonverbal tasks to assess spatial knowledge. Results indicated that landmark knowledge as asserted by the visual recognition of landmarks was not impaired by any of the concurrent task. Route knowledge, assessed by recognition of directions, was impaired both by a tapping task and a concurrent articulation task. Interestingly, the pattern was modulated when no landmarks were available to perform the direction task. A second experiment was designed to explore the role of verbal coding on the construction of landmark and route knowledge. A lexical-decision task was used as a verbal-semantic dual task, and a tone decision task as a nonsemantic auditory task. Results show that these new concurrent tasks impaired differently landmark knowledge and route knowledge. Results can be interpreted as showing that the coding of route knowledge could be grounded on both a coding of the sequence of events and on a semantic coding of information. These findings also point on some limits of Baddeley's working memory model.

Our goal is to examine the emotional influence of perceived basic motions on cognitive processes in childhood. The main hypothesis of this study proposes that the perception of motion will subsequently influence cognitive processing in a specific, emotional manner. We studied 90 children aged nine to 12 years old. On a screen they were shown a black-shaped disk moving in one of three different directions associated with positive, negative and neutral valences. Furthermore, both before and after the children had seen the motion, they were asked to perform a writing speed task (numbers counting down). The results show that (1) children attribute an emotional valence to the "positive" motion and (2) the writing speed cognitive task is influenced by the "negative" motion. Thus, we suggest that basic motions can elicit changes in emotional manner in childhood to perceptive and executive processes according to their specific trajectory. (PsycINFO Database Record (c) 2013 APA, all rights reserved).

Stereopsis was brought to the fore by its stunning development in a virtual element, in movies or game devices. The mechanisms used to produce 3D artificially are very similar to those involved in natural depth perception. They include binocular stereopsis, generated by the simultaneous perception of two images with a slight horizontal shift, together with the interpretation of monocular clues (perspective, distribution of light and shadow,...). Because virtual 3D uses the same mechanisms as natural perception, there is no reason to believe that 3D movies might be dangerous for the eyes.

Pupil size reflects the balance between sympathetic and parasympathetic systems. Due to technological advances, accurate and repeated pupil size measurements are possible using infrared, video-recorded pupillometers. Two pupil size reflexes are assessed: the pupillary reflex dilation during noxious stimulation, and the pupil light reflex when the pupil is exposed to the light. The pupillary reflex dilation estimates the level of analgesia in response to a painful procedure or to a calibrated noxious stimulus, i.e., tetanic stimulus, in nonverbal patients. This might be of particular interest in optimizing the management of opioids in anaesthetized patients and in assessing pain levels in the intensive care unit. The pupil light reflex measurement is part of the routine monitoring for severely head-injured patients. The impact of pupillometry in this condition remains to be determined.

International audience; In anorexia nervosa (AN), body distortions have been associated with parietal cortex (PC) dysfunction. The PC is also the anatomical substrate of a supramodal reference framework involved in spatial orientation constancy. Given the impaired spatial orientation constancy found in hemineglect, we sought to determine whether similar disturbances could be observed in anorexic patients. We investigated the effect of passive lateral body inclination on the tactile subjective vertical (SV). Fifty participants (25 AN patients and 25 healthy controls) were asked to manually set a rod into the vertical position under three postural conditions. For tilted conditions, we observed a significant deviation of the tactile SV towards the body. This effect was abnormally accentuated in AN patients and might be caused by higher weighting with respect to the egocentric frame of reference. Our findings reinforce the role of the PC in AN and suggest that this dysfunction affects spatial orientation constancy as well as body boundaries.

In neurosciences, there is increasing interest in studying affective, emotional and social processes in humans and animals. What are the conceptual framework identified for these studies and the technical approaches undertaken? What information has already emerged from these studies? Which results have already been obtained and what are the researchers' goals? Can these neuroimaging analyses provide novel insights to improve our understanding of psychiatric disorders? These are some of the questions addressed in this concise overview of our knowledge in this domain.

Visual field deficit (VFD) is one of the most commonly observed symptoms following brain injury. Persistent VFD and defective exploratory oculomotor scanning patterns often cause severe impairment in daily activities, particularly as regards visual exploration and reading. Homonymous hemianopia is consequently a powerful negative predictor of patient outcome. In spite of these quantitative and qualitative factors, there currently exists no consensus on rehabilitative therapy and treatment. Different approaches have nevertheless been developed, all of them having one therapeutic principle in common; repeated practice of a specific visual task, with the hope/expectation that improved performance will extend to a wide range of ecologically useful visual functions. The four main available methods aim at replacing part of the intact visual field with part of the damaged visual field (optical therapy using prisms), at partially restoring the lost visual field region (restorative therapies), at stimulating detection capacities in the blind field (stimulation or blindsight) or at substituting for the lost region by reorganizing the control of visual information processing and eye movements (compensatory therapies). This review explores the key data relative to these different approaches in terms of behavioral or imagery results. It also aims at critically analyzing the advantages and limits of each one. The importance of strict assessment in terms of deficiencies or disabilities is underlined. Finally, upon consideration of these data taken as a whole, it is suggested that efficient treatment would probably have to associate general components and more specific elements, according to what may be done with regard to other aspects of cognitive rehabilitation.

In neurosciences, there is increasing interest in studying affective, emotional and social processes in humans and animals. What are the conceptual framework identified for these studies and the technical approaches undertaken? What information has already emerged from these studies? Which results have already been obtained and what are the researchers' goals? Can these neuroimaging analyses provide novel insights to improve our understanding of psychiatric disorders? These are some of the questions addressed in this concise overview of our knowledge in this domain.

Charcot first described emotional deficits in multiple sclerosis (MS) in the XIXth century. Despite this early description, there are very few studies about emotions and MS.This study aimed at better understanding the emotional process in MS and more specifically recognition of facial emotions and emotional experience.Thirteen women with remittent MS (R-MS), with a mean EDSS score of 2, were compared with thirteen healthy control subjects, matched for age (mean age of 42±2), sex and educational level. The Beck Depression Inventory (BDI), the Hamilton Anxiety Scale and the brief repeatable battery of neuropsychological tests for MS (BCcogSEP) were administered. Recognition of faces and facial expression of emotion were assessed by the Benton facial recognition test and recognition of facial emotions was assessed by Ekman's facial expression test. We have also presented 12 different sounds and pictures from the International Affective Digitized Sounds and Picture System (IADS and IAPS) in order to study the emotional experience by using criteria of valence and arousal.No deficit of facial emotion recognition was found in MS in this small population. Nevertheless, patients who had difficulty recognizing faces were the least able to recognize facial expressions. No significant difference was observed between the patient and control group for the experience of emotional valence. However, independently of their mood and cognitive status, the self-assessment of the MS patient population suggested that the patients were less reactive to negative sounds (P=0.005) and negative pictures (P=0.002) as compared with the control group, pointing to lesser sensitivity towards aversive stimuli.These data suggest disorders in emotional processes in R-MS, mainly a poor reactivity to negative stimuli which may have an impact on everyday life. A larger population should be studied to confirm these modifications of emotion.

The emergence of brain imaging in recent years has been accompanied by an alliance between neuroscientists and marketers. This collaboration gave birth to "neuromarketing", a new field that uses imaging techniques with the aim of resolving marketing issues.Several studies have shown that pleasure felt at the sight of a product or after its consumption, is activated by a reward system involving ventral striatum. Since then, marketers seeking exploit this data and have found that some marketing actions can generate added satisfaction in a placebo-like manner. However, neuromarketing suffer from many limits that are a barrier to its development and its scope is restricted.Through this article, we attempt to give an overview on neuromarketing and its neural correlates while provide a perspective toward the use of field for less commercial purposes.The neuromarketing is a new field which efficiency is not proven. Its results must be interpreted with caution.

The authors investigated the understanding of emotion dissimulation in school-age children. Sixty participants were read short stories in which a main character expressed an emotion or hid an emotion from other characters. The participants were asked to identify the emotion felt by the main characters and to indicate the facial expressions they would display. Then they were asked what emotions the main characters felt while they were displaying these expressions, and what the beliefs of the other story characters would be as to the emotion felt by the main characters. The results revealed that children from 5 to 6 years of age have a partial understanding of emotion dissimulation. They were accurate in finding the emotion felt by the main characters when questioned the first time. They were also accurate in choosing the expressions the main characters would display to hide their emotions. However, they were often inaccurate as to the felt emotions of the main characters when questioned the second time. Compared with 9- and 10-year-olds, the younger children had more difficulty understanding the simultaneous character of felt and displayed emotions. Five- and 6-year-olds were also less accurate than the older children when asked to indicate the beliefs of the other characters in stories where felt emotions were hidden.

The present paper reviews the main studies that have been conducted on the effects of masked orthographic priming in written word recognition. Empirical data accumulated over the last two decades are exposed by considering three factors that play a role in the effects of orthographic priming: prime lexicality, prime duration, and target and/or prime orthographic neighbourhood. The theoretical implications of these data are discussed in light of the two major frameworks of visual word recognition, the serial search and the interactive activation. As a whole, the interactive activation hypothesis seems to be more appropriate to account for the empirical data.

International audience; The mammalian circadian clock, whose central component is located in the suprachiasmatic nucleus of the hypothalamus (SCN), orchestrates rhythmic events in metabolism, physiology and behavior. Adaptation of the organism to its environment requires precise adjustment of the clock to the 24 h astronomical time, primarily by the light/dark cycle. Photic synchronization acts on both the molecular loops which trigger circadian oscillations and the phasing of the multiple SCN cellular oscillators whose coordination permits elaboration of the rhythmic message that will be distributed throughout the organism. It is concomitant with structural plastic events characterized by day/night rearrangements of the SCN neuronal-glial network. The two main sources of SCN efferents, namely the VIP (vasoactive intestinal peptide)-synthesizing neurons which are major integrators of photic signals and the AVP (arginine-vasopressin)-synthesizing neurons which are known to importantly contribute to conveying rhythmic messages to brain targets, are involved in these mechanisms. Over the light/dark cycle, they indeed undergo ultrastructural changes in the extent of their membrane coverage by glial, axon terminal and/or somato-dendritic elements. These structural rearrangements appear to be dependent on light entrainment, as the rhythmic expression in SCN of glial fibrillary acidic protein (GFAP), a marker for brain astrocytes whose changing expression has proved to be a reliable index of neuronal-glial plasticity, is disrupted under constant darkness. Glucocorticoid hormones, which are known as important endocrine outputs of the clock, are required to maintain amplitude of the SCN GFAP rhythm to normal values, indicating that they modulate astrocytic plasticity within the SCN and, therefore, nycthemeral changes of the configuration of its neuronal-glial network. The view that such plastic events may subserve synchronization of the clock to the light-dark cycle is reinforced by other data showing that the daily fluctuations of circulating glucocorticoids actually are involved in modulation of light effects, contributing to the resistance of the circadian timing system to variations of the photoperiod. It is thus proposed that the capacity of the clock to integrate cyclic variations of the environment rely on the inherent capacity of the SCN to undergo neuronal-glial plasticity.

This experiment examined whether newborn stepping, a primitive form of bipedal locomotion, could be modulated by optical flow. Forty-eight 3-day-old infants were exposed to optical flows that were projected onto a horizontal surface above which the infants were suspended. Significantly more air steps were elicited by exposure to a terrestrial optical flow specifying forward translation than by a rotating optical flow or a static optical pattern. Thus, a rudimentary coupling between optical flow and stepping is present at birth, suggesting a precocious capacity in the newborn to perceive and utilize visual information specifying self-motion. The findings may help the early diagnosis of infants with visual or visual-motor deficits and the development of visually based interventions for disabled infants.

A high level of evidence does not exist for many aspects of testing for visual sensitivity. Evidenced-based studies are needed in several areas, including (i) reliability of LED-based stimulators, (ii) the most appropriate montages for displaying responses, (iii) testing during pregnancy, and (iv) the role of visual-sensitivity testing in the diagnosis of neurological disorders affecting the elderly and very elderly. Standardization of testing across the country will be an important step in filling the existing gaps of knowledge.

In Multiple Sclerosis (MS), one of the most frequent neurological diseases in young adults, cognitive dysfunctions have been under considered whereas their evolution may produce a fronto-sous-cortical deterioration and more than half of the MS patients present such dysfunctions. Nevertheless sensory evoked-potentials are classically used in this disease, event-related potentials (ERP) are not included in the clinical exploration of MS. Two studies are presented aimed at further tracking the usefulness of ERP for detecting early cognitive dysfunctions in MS. All of the patients presented a relapsing remitting MS for less than 5 years with a moderate physical handicap and complained from their memory. They performed a neuropsychological set and ERP were elicited using the oddball paradigm in both modalities, visual and auditory. In the first study, 10 patients without cognitive dysfunction at the neuropsychological evaluation and 10 patients with an attention deficit participated with 10 age-matched controls. In the second study, 10 patients with memory impairment at the neuropsychological evaluation and 10 age-matched controls were included. Our data argue for an earlier modification of ERP parameters in the visual modality than in the auditory one, even before the modification of cognitive scores. In both studies, P300 parameters were correlated to neuropsychological performances (and especially to the attention examination in the first study and to memory tests in the second study) in both modalities. Taking into account the clinical usefulness of ERPs, it is nowadays important to include this electrophysiological method in evaluation and follow-up of MS, and not only using the auditory modality but also the visual presentation in order to detect earlier cognitive dysfunctions even before modification of neuropsychological performances.

To assess the value of visual sexual stimulation combined with intracavernous injections (ICI) in patients treated for severe erectile dysfunction.All patients with severe erectile dysfunction were prospectively included in this study between 2005 and 2006. The outpatient protocol consisted of comparing the efficacy of alprostadil ICI alone on D0 and ICI combined with erotic stimulation on D8. End-points were: time to onset and rigidity of erection. A subjective score (1 to 5) was used to quantify erection.Forty patients with a mean age of 64.5 years (range: 52-70 years) were included in the study. All patients had an IIEF5 score less than 15. Erectile dysfunction was secondary to urological surgery in 35% of cases. The mean time to onset of erection was 10 min 18 s (range: 2-20 min) on D0 and 10 min 50 s (range: 2-20 min) on D8. No significant difference for rigidity and quality of erection was observed between D0 and D8 and erections were scored as 5 in 30 cases (75%), 4 in 8 cases (20%) and 3 in 2 cases (5%) at each visit.Visual sexual stimulation has not been demonstrated to be truly effective in the hospital setting in combination with intracavernous injections. In order to increase the patient satisfaction rate, the urologist must above all educate the patient in the intracavernous injection technique in an appropriate environment.

To evaluate the long-term changes in pupil size after implantation of an Artisan phakic intraocular lens for correction of high myopia.Fourteen myopic eyes of seven patients were included in the study. Pupil size was measured under photopic conditions, under scotopic conditions after 10 min of dark adaptation, and after topical medical mydriasis. The pupil size was measured using the eye image of the OPD scan (Nidek).The mean follow-up was 46 months after surgery. The mean photopic pupil diameter was 2.94+/-0.33 mm (range, 2.54-3.6 mm). The diameter of the scotopic pupil remained less than 6.0 mm in all patients (4.68+/-0.59 mm, with maximal pupil diameter of 5.67 mm). The mean pupil diameter after pharmacological dilation was also reduced (5.39+/-1.08 mm; range, 4.19-7.59 mm), with pupil dilation more than 7 mm in only one patient.The iris-fixated intraocular lens mechanically limited pupil dilation in our patients. The long-term reduction in pupil size after Artisan phakic intraocular lens implantation may contribute to the maintenance of the quality of vision in scotopic conditions.

This research centres on the effect that the orthographic neighbourhood has in the visual recognition of words. Specifically, we studied to what extent orthographic neighbourhood distribution, that is, the number of letter positions allowing formation of at least one neighbour (Pugh, Rexer, Peter,Katz, 1994), influences the masked repetition priming effect. In a previous study (Mathey, Robert,Zagar, 2004), interaction between neighbourhood distribution and orthographic priming was obtained in the lexical decision task. The Interactive Activation Model (IA; McClellandRumelhart, 1981) simulated this interaction. With the orthographic priming effect modified for distribution of the neighbourhood of target words, it was necessary to study whether the repetition priming effect also varied as a function of this indicator. Studying this interaction presents a major theoretical issue in specifying the activating and inhibiting processes presented in the IA model. Simulations were produced to obtain precise model predictions regarding the neighbourhood distribution effect in a repetitive priming situation for our experimental material. Target words all had two neighbours that were most frequent. These neighbours were isolated, that is, distributed over two letter positions (e.g.: TAUX/faux-toux), or associated, i.e., concentrated on one single position (e.g., SEAU/beau-peau). Targets were preceded by an identical priming (repetitive priming; e.g.: seau-SEAU) or by controlled priming (e.g.,-SEAU). The simulation results obtained using the IA model show the facilitating effects of neighbourhood distribution and repetitive priming, but no interaction between these factors. The experimental results obtained in a lexical decision task confirm these predictions. Thus, the empirical data replicate the neighbourhood distribution's facilitating effect (MatheyZagar, 2000) as well as the facilitating effect of masked repetition (ForsterDavis, 1984). Finally, the most interesting result is that the facilitating effect of repetition is comparable for target words with associated neighbours and target words with isolated neighbours. An explanation of the combined effects of the orthographic neighbourhood and orthographic masked repetition priming, integrating data from literature as well as from the current study, is proposed within the framework of the IA model.

PURPOSE AND MATERIALS: To evaluate the cortical response to visual stimulation in patients with age-related macular degeneration (ARMD), we conducted a functional MRI study in ten patients presenting unilateral or bilateral ARMD and five age-matched controls, using white flashes during activation phases (see Part I).After anatomical conformation, eight patients and four controls showed significant cortical hemodynamic response to monocular stimulations. Individual analysis was preferred to group evaluation, because of the differences in visual loss in a small number of patients. In controls, we observed cortical response in the primary visual cortex, especially at occipital poles corresponding to the macula. Patients showed a qualitative and quantitative restriction in cortical response and exclusion of occipital poles after stimulation of the affected eye, whereas activation was found in the peripheral striate and peristriate cortex. Cortical response showed hemispheric asymmetry in some patients.Our study demonstrated an activation defect in the macular projected striate cortex, corresponding to visual impairment in ARMD patients. Nevertheless, at a given visual acuity, cortical response may vary among subjects. Patients' subjective apprehension may account for such variations, as well as objective visual capacity stemming from residual functional retinal areas within the affected macula. The hemispheric asymmetry in cortical activation may result from gaze deviation onto the new fixation area in the perimacular retina, thus altering the global visual field. Enhancement in the peripheral striate and peristriate areas suggests changes in cortical interactions, possibly by a lowering of the feedback from macular projected V1. Finally, cortical evaluations must take into account degenerative phenomena delaying the hemodynamic response in the elderly.Aiming at a specific population of weakened patients with a serious visual impairment, we obtained significant results concerning cortical plasticity for visual perception in central vision deletion. Our preliminary findings must be confirmed in a larger population and correlated with other techniques exploring vision, in particular with multifocal electroretinography for retinal evaluation.

The cognitive event-related potentials were studied in a group of 55 alcoholic patients, paired in age and sex with a group of 18 control subjects, using a protocol oddball (visual and auditory) and a protocol VCN Go/Nogo. The N200 obtained using an auditory oddball paradigm had lower amplitude in alcoholics than in controls. A significant amplitude decrease of visual P300 was also observed in alcoholic male subjects. There was however no difference in auditory P300 between alcoholics and control subjects. Using a Go/Nogo paradigm, a significant difference on the final part of the VCN appears between alcoholic and pilot subjects. In addition, the longitudinal follow-up of the same alcoholic patients showed an electrophysiological profile that allowed dividing them into two different groups. On the initial recording (17 days after weaning), the auditory oddball P300 amplitude was significantly higher at Cz and Pz among patients who relapsed during the 3 months follow-up. The same effect appeared on the CNV protocol, where the amplitude of P300 was higher in patients who subsequently relapsed than for those who remained abstinent. Cognitive ERPs may be clinically useful to improve the prediction of risk of relapse among alcoholic patients.

The Stroop color-word test is often used to assess attentional function. In this study we investigated whether dyschromatopsia affects the results of this test, and in that case which are the attentional consequences of this color-vision trouble. Event-related potentials were recorded on 19 dyschromatopsic subjects when submitted to a video-displayed Stroop test, and compared to those of 19 control subjects. Results showed that reaction times of dyschromatopsic subjects, although generally longer than those of controls, had normal interference and facilitation effects. Potentials evoked by neutral stimulations were delayed for P2 and P3 waves, and those evoked by word-containing stimulations showed delays for N2b (N320) and P3 waves. The premotor potential appeared modified in dyschromatopsic patients, whereas error negativities, or correct response negativities were identical to those of control subjects. We conclude that dyschromatopsia affects negatively the performance in the Stroop test, at sensory levels which are reflected by evoked potentials, but without important consequences on attentional function. In particular, dyschromatopsia did not alter significantly the attentional focusing on the chromatic aspects of the stimulus.

To determine the response of human optic nerve head (ONH) blood flow (delta F) to heterochromatic equiluminant flicker modulation (eql-fl) and compare it to the response induced by pure luminance flicker (l-fl).In 5 normal volunteers the ONH blood flow was measured by conventional laser Doppler flowmetry. Stimuli were generated by green and red light emitting diodes and delivered to the eye through a fundus camera illumination optic. Both green and red illuminances were square wave modulated in counter phase at different frequencies between 2 and 40 Hz. delta F was defined as the ratio between the ONH blood flow after 1 min stimulation and a baseline blood flow measured prior to the stimulation.In response to a 2 Hz eql-fl, ONH blood flow increases by 36% in average. delta F versus flicker frequency displayed the characteristics of a low-pass function with a cutoff frequency of 10 Hz for an eql-fl and a band-pass function with broad maximum around 10 Hz for the I-fl.delta F in human ONH can be evoked by heterochromatic equiluminant flicker modulation. The blood flow frequency response to eql-fl and I-fl are similar to the neural activity dominated by the Parvo- and Magno-cellular activity, respectively. These findings offer a new approach to study the neurovascular coupling at the ONH in both physiological and diseased conditions involving predominantly or selectively the Magno- and Parvo-pathways.

Morphoscopic perception at variable contrast and luminance levels has been assessed in various diseases and in occupational medicine. To our knowledge, this function has not been studied in young adults of similar age. We performed a prospective study to assess morphoscopic perception at variable contrast and luminance levels in a group of young servicemen.A total of 97 subjects (194 eyes) with a mean age of 22.4 (standard deviation 1.16) years were assessed with the Gradual monitor. After visual acuity was measured, morphoscopic perception was assessed at a mean light level of 85 cd/m2, at low, medium and high spatial frequencies, with myopic correction. All subjects whose visual acuity was not correctable to 10/10 in both eyes or whose score was statistically too different from the mean underwent a complete ophthalmologic examination.Overall, 87 subjects had a visual acuity correctable to 10/10 or better in both eyes. For 34 of the 87, at least one of the six scores was more than 1 standard deviation below the mean; however, for 16 subjects the result was within normal limits after minor adjustment of the correction, often of a small degree of astigmatism. Of the 18 remaining subjects 7 had microstrabismus, 8 had anatomic lesions and 3 had lesions of unknown origin. Of the 13 subjects with a visual acuity of less than 10/10, 5 had relative amblyopia, 2 had major ametropia, 2 had unilateral and 2 bilateral ophthalmologic lesions, and 2 had reduced acuity of unknown cause.In this young population the most frequent cause of reduced contrast sensitivity (40%) was associated with minor uncorrected or badly corrected refractive problems. The next most frequent cause was problems with binocular vision, with or without amblyopia (11%). In these subjects contrast sensitivity was reduced in the nondominant eye and, in five cases, in the dominant eye also.

Photosensitivity is defined by the appearance of occipital or more diffuse electroencephalographic spikes and waves induced by intermittent light stimulation (ILS), particular patterns, TV-watching, and video games. Photosensitivity is a genetic characteristic. Only the diffuse spikes and waves induced by ILS are correlated with epilepsy. Pure photogenic epilepsy is characterized by seizures which are only visually induced, usually by watching TV. Video games sometimes add a trigger effect due to slowly moving patterns or intense brightness. Several epileptic syndromes are associated with a photosensitivity with or without visually-induced seizures, mainly generalized idiopathic epilepsy.

Event-related potentials (ERPs) studies in human subjects have shown inter-individual response variations, probably linked to anatomical and functional brain disparities. The present study was conducted to compare the results obtained by a standard grand-average method and a single subject analysis of VEPs to faces.Fifty-eight channel ERPs (analysis time: 1,024 ms) were recorded in 13 normal volunteers during gender or familiarity judgements on unknown and known faces, as well as on a control task using meaningless patterns. Data were then submitted to individual and group averages.Three activities were identified by both procedures: a P1/N1 complex, a vertex positive potential (P2 or VPP) associated with a temporal negativity, and a N2 negativity. These peaks displayed a marked inter-individual topographical variability. Regarding the outcome of statistical analyses, a certain number of differences were found: on P1, in which individual analyses revealed a strong effect of experimental conditions, while the grand-average method did not; on VPP, in which grand-average analyses suggested an interaction between experimental conditions, face familiarity and cerebral lateralization, while individual analyses did not; and on N2, in which grand-average data showed a clear lateralization effect, while individual analyses did not. A P3 component (Pz, 250 ms) was also defined in grand-average data, but could not be clearly described in individual data. Statistical analyses on this P3 component were thus only performed on group data and revealed a right lateralization and an interaction between face familiarity and experimental conditions. These findings confirmed the existence of a marked topographical variability of ERPs to face and, therefore, question the validity of grand-average studies. Moreover, these results suggest a better efficiency of individual analyses for studying short and middle-latency peaks, while grand-averages appear to be better suited for studying late components.

The aim of this study was to examine selective attention in patients with chronic and refractory schizophrenia who had been exposed for six months to atypical neuroleptic medications: risperidone or clozapine.17 patients satisfying DSM III-R criteria for schizophrenia were assessed according to BPRS and PANSS and abnormal involuntary movements to ESRS. Selective attention tasks were performed before treatment with risperidone or clozapine and at two times during the treatment (6 weeks, T1, and 24 weeks, T2). Patients' performance data were compared to data from a group of general population at T1. Selective attention refers to the ability to discriminate relevant information from irrelevant one. This was measured by a visual search task. Subjects had to search for a target specified by a conjunction of features (color and shape). The target was a black X, while the distracters were white X's, black O's and white O's. The stimuli were displayed on a Macintosh SE computer. A two-button response box was used for response production and the experiment was run in a dimly lit room. A white-fixation stimulus was shown at the center of the display screen between trials. The number of stimuli displayed on a single trial was 1, 4, 7 or 10. The median RTs and error rates of subjects were computed for each factor (target presence and number of stimuli).A Group X Number of items X Presence of target ANOVA applied on median correct RTs revealed a significant Group X Presence interaction [F(1,176) = 60.433, p.0001]. Performances improved with the time (F2, p.01). Correlations were found between positive score on PANSS and performance on selective attention (r39 = -.391).Atypical neuroleptic do not have a deleterious effect on selective attention but a favorable effect on the schizophrenic patients' performance.

Photosensitivity is defined by a pattern of occipital or more diffuse spikes and waves. Several techniques are needed for exploration: intermittent light stimulation (ILS), patterns, TV-screen, video games. Photosensitivity is a genetic characteristic. Only diffuse spikes and waves induced by ILS are correlated with epilepsy. Pure photogenic epilepsy is characterized by seizures induced by visual stimuli alone, usually by TV-screen. Video games may also have a triggering effect due to the slow-moving patterns or intense brightness. Several epileptic syndromes are associated with photosensitivity with or without visually-induced seizures. These syndromes are most often generalized and idiopathic.

The aim of the present study was to investigate Parkinsonians' ability to process and use the explicit and implicit advance information available about a motor task they are preparing to perform. For this purpose, the performances of 13 Parkinsonians were compared with those of 11 control subjects in a double stimulus reaction time task. The explicit information was provided by a preparatory auditory signal (S1), and the implicit information was conveyed by the probability that the imperative signal (S2) would be consistent with S1 in a given series of trials. Each subject performed 3 successive RT tasks under the following conditions: an oriented cue condition, a neutral cue condition and a primed condition. The results show that the movement times of the Parkinsonians were longer than those of the control subjects, and that they lengthened with the clinical evolution of the disease. Neither the explicit nor the implicit advance information had any effect on the control subjects' performance variables; nor did they affect the Parkinsonians' movement times or pointing areas. The Parkinsonians' systematic errors increased however in the case of primed responses. The fact that the patients' bradykinesia was associated with fairly accurate pointing performances suggests that in Parkinson's disease, a change of voluntary movement performance strategy may occur, involving greater reliance on visual cues.

The Stroop test is based on interference between reading and naming of incongruent color words. To decide whether this conflict was of perceptual or motor origin, event-related potentials were simultaneously recorded. Since the components of these potentials are dependent on the progression of information processing, their changes related with the nature of the stimulation should provide information about the mechanisms underlying the conflict. Evoked potentials were recorded from three midline leads in 18 healthy subjects during reading and naming tasks. The 216 stimulations were the words "red, green and blue" presented in either a congruent or incongruent color, or in a neutral color. The behavioral Stroop effect did not affect the P300 latency, suggesting that the conflict occurs in the motor system. This was supported by the presence of a premotor negativity for incongruent stimulations, occurring between 400 and 205 ms before button press, and present in the naming condition only. Moreover, for the two conditions, congruent stimulations evoked positive potentials between 260 and 310 ms at the level of the occipital lead for reading and at the level of the frontal lead for naming. The possibility of an interaction of specialized channels for stimulation analysis at an early level is raised.

Previous studies have demonstrated, in the cat, a vasodilatation of retinal vessels in response to neuronal activity induced by diffuse luminance flicker. The aim of this study was to determine whether a similar diameter variation is detectable in humans.Nine normal subjects were exposed to 1 min of sinusoidally varying diffuse luminance flicker (10 Hz, 30 degrees around optic nerve head). Monochromatic fundus pictures before and after the stimulation were taken. The diameter of retinal arteries and veins was measured on the digitised photographs with the NIH-Image software and an own algorythm.The diameter immediately after flicker was significantly larger than the pre-stimulus diameter by 4.2 +/- 2.2% (p0.014) (mean +/- SD) for the retinal arteries and 2.7 +/- 1.7% (p0.001) for the retinal veins. Six seconds after cessation of the flicker, arterial diameter was not significantly different from that of pre-flicker value.Diffuse luminance flicker induces an increase in retinal vessel diameter. This suggest that retinal blood flow is coupled with neuronal activity as previously evidenced by the blue field simulation technique in the macula.

Gait analysis of 13 patients affected by Parkinson's disease (PD) and 7 healthy elderly volunteers was performed with a fully automatic motion analyser. The recording included stride parameters for walking velocity, stride length, stride duration and swing time. Maximal amplitudes of rotation of the hip, knee and ankle were also recorded. The analysis was performed for the PD's patients before and after L-Dopa intake. All the patients walked with and without transversal stripes on the floor. The contrasting white lines were 45 cm apart. After medication, the stride length, the velocity and the swing phase duration were significantly increased. The movements around the hip, knee and ankle joints that were initially reduced, poorly increased after L-Dopa intake. When stripes were placed on the floor, no significant changes occurred for the overall group of patients. Seven parkinsonian patients did improve with visual guidance, increasing their stride length and their speed. Some rotations of hip and knee were also influenced by stripes. This sub-group of patients was characterized by older age, a slower walking velocity, a smaller stride length and a shorter swing time. We correlated the sensitivity to visual cues to the defect of the visual contrast sensitivity that has been established in PD by several recent works. Locomotion on the transverse lines might have produced a motion perception at a rate determined by the speed of the patient. For appropriate intervals between stripes, one can hypothesise that the resulting visual stimuli belonged to a range of spatio-temporal frequencies that are decreased in patients with PD.

The normal development of the visual system from birth until the end of the critical period involves, for the young subject to achieve a number of visual experiments. In cases of late blindness, the visual system has been normally developed, which is not the case when early blindness is considered where an abnormal cerebral organization exists. Accordingly, attempts to rehabilitate vision in the blind have to consider these discrepancies. When the invasive visual prosthesis acting by electrical stimulation of spared parts of the visual system is suitable in case of late blindness, sensory substitution prostheses coding visual information into signals addressing an intact sensory modality seems devoted to cases of early blindness. This later approach takes into account the early blind's brain specific organization, whose undeveloped occipital cortex has been shown to be involved in the sensory substitution process using positron emission tomography.

Functional activation of the cerebral cortex can be observed with a standard 1.5 Tesla MRI magnet. We used a repeated FLASH 2D one-section sequence with a long echo (TE = 60 ms) and a small passing band. Modification of regional cerebral oxygenation due to neurone activation seems to be the main source of contrast. Sensorimotor stimulation was effected by an unusual mobilization of the fingers. Visual stimulation was performed by intermittent lightings at a frequency of 8 Hz. Auditory stimulation relied on listening to speech sounds. Signal increases were localized on the cerebral cortex with precise anatomico-functional correlation. Using a clinical 1.5 Tesla magnet requires an adequate treatment of data. Thus, stimulated cerebral activity can be portrayed by MRI therapy opening a new way for anatomico-functional cerebral studies.

Units of the caudate and putamen were studied during stereotactic operations in 11 patients with movement disorders. Responses of these units to different visual stimuli were found for cells of the caudate nucleus head. These units were activated mainly during the presentation of nutritional stimuli. The responses appeared when a slide was shown presenting an image of drink or food or the corresponding word. Frequently the same unit was activated by slides of the image and the word presented in succession. Responses to similar stimulations were not observed in the putamen. Among the parkinsonian patients, only those with tremor had responsive cells while the rigid patients had not. This discrepancy was correlated with the lowering of cortical metabolism demonstrated by PET scan in the rigid group of patients. These results are in agreement with those obtained in monkeys during food presentation. They present, moreover, the advantage of showing that these responses could be provoked in man by more abstract stimuli, not only the image but the name of the object. These observations do not imply a long testing period; 2 or 3 cells only are studied in each patient. They have the advantage for the patient of ascertaining the position of the trajectory in the striate structure, in the same way as thalamic nuclei are delineated using other types of stimuli. Moreover, it is of interest to have a better knowledge of the behavioral role played by different striatal regions at a time when lesions or stimulations at this level are proposed to cure abnormal movements in human.

The authors have reviewed the main effects of anaesthetic agents on sensory evoked potentials (EPs) in the auditory, somatosensory and visual modalities. Knowledge of EP changes induced by anesthetic drugs is important to avoid false alarms when monitoring neural structures at risk during surgery. Intraoperative EP monitoring is all the more efficient as the following points are taken into account: 1) whatever the sensory modality considered, EPs are more attenuated by volatile halogenated agents than by intravenous drugs; 2) the cortical components of EPs are more sensitive to anesthetic drugs than the brainstem components; 3) in each modality, the first component of the "primary cortical complex" is less attenuated by anaesthetic agents than the following cortical waves; 4) continuous administration of anaesthetic agents rather than acute administration (bolus) is preferred during EP monitoring. EPs also represent an objective means to assess the depth of surgical anaesthesia, since they may provide a reliable index of cortical depression. Amplitude changes of middle-latency auditory responses (Pa/Nb) seem to be a good marker for estimating depth of anaesthesia with the aid of EPs.

Pursuit eye movements have been recorded with the photo-oculographic technique from newborn infants during the presentation of stimulations specific for spatial discrimination functions. 72.5 per cent of 51 subjects whose eye movements have been recorded have successfully followed stimuli of spatial frequency up to 0.4 cycles per degree. Estimations of grating visual acuity are similar to those provided by the preferential looking technique.

In response to a visual stimulation, "replicated triplets" of impulses may appear in many spike trains recorded from the cat dorsal lateral geniculate nucleus (dLGN). The number and the temporal structure of these triplets depend upon the general organization of the geniculate impulse trains. In this study, we show that a pharmacological blockade of the corticothalamic activity, obtained through microinjection of GABA into area 17, affects the replicated triplet production and leads to an increase in the dispersal of their structure. These results suggest that the corticothalamic pathway closely influences the fine temporal organization of the geniculate messages.

We have studied visual evoked potentials (VEP) in four groups: healthy young and aged subjects and aged patients suffering from depression or Alzheimer's disease (AD). In the flash modality, peak IV delay in AD patients as compared to aged controls corresponded to lengthened III-IV interlatency (IL). When AD and depressed patients were compared, peak IV delay in the former did not reach significance. Normal aging resulted in delayed peaks II and III, without IL modification. In the pattern reversal modality, no difference was observed between AD patients and aged, healthy or depressed controls. Aging delayed peaks P50 to P180. The abnormality exhibited by AD patients was specific to this group. However, the lack of significant difference between AD and depressed groups argues against the ability of VEP to differentiate those conditions.

This study shows the possibility of obtaining visual event-related potentials without active discrimination instructions. The components are similar to the P3 components obtained in classic active protocol. The (P3off) of simple images indicates an interpretation in terms of information processing and change in mental state.

The postural displacements on a statokinesimetric plateform of squint-eyed children during short monocular lighted stimulations show that their postural regulation is different from that of normal children of the same age. The provoked amplification of the displacements is larger, their direction is no more systematized but once adopted it remain stable. The orthoptic treatment associated with prismus lenses and postural reeducation often allows to double their postural performances.

The performances of 14 hebephrenic patients and 14 normal subjects were studied through visual and auditory tests concerning the comparison of the number of stimuli projected either in the left, or in the right, or in both cerebral hemispheres. Schizophrenic patients were less efficient than normal subjects and, in both populations, no difference in the performances with regard to the locus of projection was observed. This suggests that information processing in schizophrenia might be deficient not only at the level of interhemispheric connections, but also in intrahemispheric functioning.

When measured with double-barreled ion-selected microelectrodes, delta K+0 is found to be heterogeneously distributed over the retinal surface. A transient fall (less than or equal to 200 microM) in delta K+0 near an arteriole wall and a transient increase (less than or equal to 500 microM) in zones free of arterioles were observed during light stimulation. In view of these findings the authors assume that the former is due to K+ uptake and transport by perivascular astrocytes, and that the latter is due to K+ siphoning by Müller cells.