Unilateral Right Parietal Damage Leads to Bilateral Deficit for High-Level Motion

AbstractPatients with right parietal damage demonstrate a variety of attentional deficits in their left visual field contralateral to their lesion. We now report that patients with right lesions also show a severe loss in the perception of apparent motion in their “good” right visual field ipsilateral to their lesion. Three tests of attention were conducted, and losses were found only in the contralesional fields for a selective attention and a multiple object tracking task. Losses in apparent motion, however, were bilateral in all cases. The deficit in apparent motion in the parietal patients supports previous claims that this relatively effortless percept is mediated by attention. However, the bilateral deficit suggests that the disruption is due to a bilateral loss in the temporal resolution of attention to transient events that drive the apparent motion percept

Emotional Facial Expression Detection in the Peripheral Visual Field

BACKGROUND: In everyday life, signals of danger, such as aversive facial expressions, usually appear in the peripheral visual field. Although facial expression processing in central vision has been extensively studied, this processing in peripheral vision has been poorly studied. METHODOLOGY/PRINCIPAL FINDINGS: Using behavioral measures, we explored the human ability to detect fear and disgust vs. neutral expressions and compared it to the ability to discriminate between genders at eccentricities up to 40°. Responses were faster for the detection of emotion compared to gender. Emotion was detected from fearful faces up to 40° of eccentricity. CONCLUSIONS: Our results demonstrate the human ability to detect facial expressions presented in the far periphery up to 40° of eccentricity. The increasing advantage of emotion compared to gender processing with increasing eccentricity might reflect a major implication of the magnocellular visual pathway in facial expression processing. This advantage may suggest that emotion detection, relative to gender identification, is less impacted by visual acuity and within-face crowding in the periphery. These results are consistent with specific and automatic processing of danger-related information, which may drive attention to those messages and allow for a fast behavioral reaction

Évolutions à moyen et court termes (XIXè – XXè) de l’avant-plage du secteur littoral de Combrit – Île-Tudy (Finistère) : Aspects méthodologiques, dynamiques et essai d’interprétation

National audienceL’objet de cette présentation porte sur l’évolution morphologique des avant-plages. Elles font parties intégrantes des accumulations littorales, comprenant les plages et les accumulations de haut de plage. Néanmoins, pour des raisons d’accessibilité limitée pour les observations scientifiques, les avant-plages sont encore relativement peu étudiées comparativement à la partie émergée du système. L’avant-plage du secteur de Combrit – Île-Tudy, dans le sud du Finistère, en est un bon exemple. Les objectifs de cette étude sont dans un premier temps de développer une méthode permettant l’utilisation de levés bathymétriques anciens (fourni par le Service Hydrographie et Océanographique de la Marine) en prenant en compte toutes les imprécisions induites par ce type de données. Dans un deuxième temps, il s’agit de mettre en évidence des évolutions morphologiques, par la comparaison des données anciennes (XIXè et XXè siècle) et récentes (2012, 2013 et prévue pour 2014). La comparaison de Modèles Numériques de Terrain (MNT), permet d’identifier trois situations : une situation d’érosion de l’avant-plage entre 1818 et 1903, un exhaussement généralisé des petits fonds entre 1903 et 1971 et un retour à l’abaissement entre 1971 et 2012. A la suite de ces résultats, les causes de ces modifications sont abordées au travers de différentes hypothèses. En effet, plusieurs facteurs sont susceptibles d’avoir une action directe ou indirecte sur la morphologie de l’avant-plage. On peut citer par exemple des facteurs naturels (modification du régime de houle et impacts des évènements météo-marins majeurs) et des facteurs anthropiques (extractions de sable et poldérisation)

Cortical dynamics of a self driven choice: a MEG study during a card sorting task.

International audienceOBJECTIVE: The aim of this study was to disclose the dynamics of the frontal processes involved in a task shifting between two attentional states. METHODS: Magnetoencephalographic activities were recorded during a Wisconsin Card Sorting Test where subjects had to match card stimuli according to one of three possible dimensions ("maintained condition"). The matching dimension was intermittently changed and subjects, after feedback presentation, had to identify the new correct dimension ("shifted condition"). RESULTS: Source activations following the feedback to the subject's response in these two attentional conditions did not differ before 350 ms post feedback. After 350 ms, in the shifted condition, a lateral/posterior frontal activation was maintained later, while a medial/anterior frontal activation appeared up to 450 ms. CONCLUSIONS: The dynamics of activities corresponding to the two conditions disclose a spread of activation from posterior lateral frontal in the "maintained condition" to anterior medial frontal in the "shifted condition". SIGNIFICANCE: These results are consistent with fMRI results concerning the major involvement of medial frontal cortex in tasks involving reasoning and choice making

Disentangling sensory precision and prior expectation of change in autism during tactile discrimination

Abstract Predictive coding theories suggest that core symptoms in autism spectrum disorders (ASD) may stem from atypical mechanisms of perceptual inference (i.e., inferring the hidden causes of sensations). Specifically, there would be an imbalance in the precision or weight ascribed to sensory inputs relative to prior expectations. Using three tactile behavioral tasks and computational modeling, we specifically targeted the implicit dynamics of sensory adaptation and perceptual learning in ASD. Participants were neurotypical and autistic adults without intellectual disability. In Experiment I, tactile detection thresholds and adaptation effects were measured to assess sensory precision. Experiments II and III relied on two-alternative forced choice tasks designed to elicit a time-order effect, where prior knowledge biases perceptual decisions. Our results suggest a subtler explanation than a simple imbalance in the prior/sensory weights, having to do with the dynamic nature of perception, that is the adjustment of precision weights to context. Compared to neurotypicals, autistic adults showed no difference in average performance and sensory sensitivity. Both groups managed to implicitly learn and adjust a prior that biased their perception. However, depending on the context, autistic participants showed no, normal or slower adaptation, a phenomenon that computational modeling of trial-to-trial responses helped us to associate with a higher expectation for sameness in ASD, and to dissociate from another observed robust difference in terms of response bias. These results point to atypical perceptual learning rather than altered perceptual inference per se, calling for further empirical and computational studies to refine the current predictive coding theories of ASD

Neuroanatomical Correlates of Recognizing Face Expressions in Mild Stages of Alzheimer's Disease

Early Alzheimer's disease can involve social disinvestment, possibly as a consequence of impairment of nonverbal communication skills. This study explores whether patients with Alzheimer's disease at the mild cognitive impairment or mild dementia stage have impaired recognition of emotions in facial expressions, and describes neuroanatomical correlates of emotion processing impairment. As part of the ongoing PACO study (personality, Alzheimer's disease and behaviour), 39 patients with Alzheimer's disease at the mild cognitive impairment or mild dementia stage and 39 matched controls completed tests involving discrimination of four basic emotions-happiness, fear, anger, and disgust-on photographs of faces. In patients, automatic volumetry of 83 brain regions was performed on structural magnetic resonance images using MAPER (multi-atlas propagation with enhanced registration). From the literature, we identified for each of the four basic emotions one brain region thought to be primarily associated with the function of recognizing that emotion. We hypothesized that the volume of each of these regions would be correlated with subjects' performance in recognizing the associated emotion. Patients showed deficits of basic emotion recognition, and these impairments were correlated with the volumes of the expected regions of interest. Unexpectedly, most of these correlations were negative: better emotional facial recognition was associated with lower brain volume. In particular, recognition of fear was negatively correlated with the volume of amygdala, disgust with pallidum, and happiness with fusiform gyrus. Recognition impairment in mild stages of Alzheimer's disease for a given emotion was thus associated with less visible atrophy of functionally responsible brain structures within the patient group. Possible explanations for this counterintuitive result include neuroinflammation, regional β-amyloid deposition, or transient overcompensation during early stages of Alzheimer's disease

Percentage of correct responses in the three discrimination tasks as a function of eccentricity.

<p>Vertical bars represent standard errors of the mean values.</p

Description of a trial: A fixation stimulus (a house picture) centrally presented for 600 ms, is followed by the target stimulus presented for 140 ms.

<p>The fixation stimulus is then presented until the subject's response.</p

Reaction times as a function of eccentricity in the three discrimination tasks:

<p>* marks a significant difference between gender and fear discrimination reaction times, § a significant difference between gender and disgust discrimination reaction times. Vertical bars represent standard errors of the mean values.</p

Caractérisation des aléas littoraux d’érosion et de submersion en Bretagne par l’approche historique

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