A network of occipito‐temporal face‐sensitive areas besides the right middle fusiform gyrus is necessary for normal face processing

Neuroimaging studies have identified at least two bilateral areas of the visual extrastriate cortex that respond more to pictures of faces than objects in normal human subjects in the middle fusiform gyrus [the ‘fusiform face area' (FFA)] and, more posteriorly, in the inferior occipital cortex [‘occipital face area' (OFA)], with a right hemisphere dominance. However, it is not yet clear how these regions interact which each other and whether they are all necessary for normal face perception. It has been proposed that the right hemisphere FFA acts as an isolated (‘modular') processing system for faces or that this region receives its face‐sensitive inputs from the OFA in a feedforward hierarchical model of face processing. To test these proposals, we report a detailed neuropsychological investigation combined with a neuroimaging study of a patient presenting a deficit restricted to face perception, consecutive to bilateral occipito‐temporal lesions. Due to the asymmetry of the lesions, the left middle fusiform gyrus and the right inferior occipital cortex were damaged but the right middle fusiform gyrus was structurally intact. Using functional MRI, we disclosed a normal activation of the right FFA in response to faces in the patient despite the absence of any feedforward inputs from the right OFA, located in a damaged area of cortex. Together, these findings show that the integrity of the right OFA is necessary for normal face perception and suggest that the face‐sensitive responses observed at this level in normal subjects may arise from feedback connections from the right FFA. In agreement with the current literature on the anatomical basis of prosopagnosia, it is suggested that the FFA and OFA in the right hemisphere and their re‐entrant integration are necessary for normal face processin

High precision astrometry mission for the detection and characterization of nearby habitable planetary systems with the Nearby Earth Astrometric Telescope (NEAT)

(abridged) A complete census of planetary systems around a volume-limited sample of solar-type stars (FGK dwarfs) in the Solar neighborhood with uniform sensitivity down to Earth-mass planets within their Habitable Zones out to several AUs would be a major milestone in extrasolar planets astrophysics. This fundamental goal can be achieved with a mission concept such as NEAT - the Nearby Earth Astrometric Telescope. NEAT is designed to carry out space-borne extremely-high-precision astrometric measurements sufficient to detect dynamical effects due to orbiting planets of mass even lower than Earth's around the nearest stars. Such a survey mission would provide the actual planetary masses and the full orbital geometry for all the components of the detected planetary systems down to the Earth-mass limit. The NEAT performance limits can be achieved by carrying out differential astrometry between the targets and a set of suitable reference stars in the field. The NEAT instrument design consists of an off-axis parabola single-mirror telescope, a detector with a large field of view made of small movable CCDs located around a fixed central CCD, and an interferometric calibration system originating from metrology fibers located at the primary mirror. The proposed mission architecture relies on the use of two satellites operating at L2 for 5 years, flying in formation and offering a capability of more than 20,000 reconfigurations (alternative option uses deployable boom). The NEAT primary science program will encompass an astrometric survey of our 200 closest F-, G- and K-type stellar neighbors, with an average of 50 visits. The remaining time might be allocated to improve the characterization of the architecture of selected planetary systems around nearby targets of specific interest (low-mass stars, young stars, etc.) discovered by Gaia, ground-based high-precision radial-velocity surveys.Comment: Accepted for publication in Experimental Astronomy. The full member list of the NEAT proposal and the news about the project are available at http://neat.obs.ujf-grenoble.fr. The final publication is available at http://www.springerlink.co

The epidemiology of mild cognitive impairment (MCI) and Alzheimer’s disease (AD) in community-living seniors: protocol of the MemoVie cohort study, Luxembourg

BACKGROUND: Cognitive impairment and Alzheimer’s disease (AD) are increasingly considered a major public health problem. The MemoVie cohort study aims to investigate the living conditions or risk factors under which the normal cognitive capacities of the senior population in Luxembourg (≥ 65 year-old) evolve (1) to mild cognitive impairment (MCI) – transitory non-clinical stage – and (2) to AD. Identifying MCI and AD predictors undeniably constitutes a challenge in public health in that it would allow interventions which could protect or delay the occurrence of cognitive disorders in elderly people. In addition, the MemoVie study sets out to generate hitherto unavailable data, and a comprehensive view of the elderly population in the country. METHODS/DESIGN: The study has been designed with a view to highlighting the prevalence in Luxembourg of MCI and AD in the first step of the survey, conducted among participants selected from a random sample of the general population. A prospective cohort is consequently set up in the second step, and appropriate follow-up of the non-demented participants allows improving the knowledge of the preclinical stage of MCI. Case-control designs are used for cross-sectional or retrospective comparisons between outcomes and biological or clinical factors. To ensure maximal reliability of the information collected, we decided to opt for structured face to face interviews. Besides health status, medical and family history, demographic and socio-cultural information are explored, as well as education, habitat network, social behavior, leisure and physical activities. As multilingualism is expected to challenge the cognitive alterations associated with pathological ageing, it is additionally investigated. Data relative to motor function, including balance, walk, limits of stability, history of falls and accidents are further detailed. Finally, biological examinations, including ApoE genetic polymorphism are carried out. In addition to standard blood parameters, the lipid status of the participants is subsequently determined from the fatty acid profiles in their red blood cells. The study obtained the legal and ethical authorizations. DISCUSSION: By means of the multidisciplinary MemoVie study, new insights into the onset of cognitive impairment during aging should be put forward, much to the benefit of intervention strategies as a whole

Le déplacement de l'attention par le regard : approche électrophysiologique

Cette thèse se situe dans le domaine des sciences cognitives et se focalise sur les yeux en tant qu'objet de perception visuelle. Le regard reflète ce que l'autre voit, ce sur quoi il porte son attention, avec quoi ou qui il agit ou communique. Dans ce sens, les informations directionnelles qui émanent du regard d'autrui sont capitales pour l'observateur, car celui-ci peut ainsi déterminer si l'objet d'attention est intéressant ou dangereux pour lui-même. Après avoir décrit la particularité des ascpects morphologique du regard humain et les mécanismes de bas niveau qui peuvent coder la direction de celui-ci, l'introduction théorique passe brièvement en revue les aspects phylogénétiques et dévelopementales de la capacité à détecter, à suivre et à interpréter un regard. Les études en neurophysiologie cellulaire et en imagerie cérébrale fonctionnelle ont permis de déterminer que la perception du regard repose sur un réseau anatomique largement distribué. Les propriétés comportementales du déplacement automatique de l'attention par le regard sont discutées en profondeur et mettent en évidence que le regard est un indicateur directionnel particulièrement puissant. Quel est le décours temporel de cette orientation particulière de l'attention ? Telle est la question centrale de la partie expérimentale de cette thèse, à laquelle nous avons tenté de répondre en utilisant la technique des potentiels évoqués. Dans une première expérience, nous avons mis en évidence que l'attention déclenchée par la perception du regard intervient à un niveau précoce du traitement de l'information visuelle. En effet, nous observons non seulement des effets comportementaux de l'attention déplacée par le regard, mais nos résultats électrophysiologiques révèlent que ces effets attentionnelles se manifestent à un niveau très précoce du traitement senoriel de l'information visuelle. Cette modulation possède la particularité de s'exprimer par des effets d'amplitude et de latence. La deuxième étude montre que ces effets sensorielles précoces s'obtiennent également par un regard statique. De plus cette étude spécifie, grâce à l'utilisation d'une condition neutre, que l'attention déplacée par la direction du regard agit par facilitation du traitement de l'information visuelle. Dans la troisième étude nous avons examiné le début exact de ces effets attentionnels. En stimulant le champ visuel supérieur et inférieur, nous avons mis en évidence la composante C1, qui se manifeste entre 40-et 60 ms post-stimulus. Elle représente le premier volet afférent de l'activité visuel au niveau du cortex visuel primaire. Les résultats ne montrent pas d'effets attentionnels sur cette composante. En conclusion nos études ont permis de mettre en évidence le décours temporel du déplacement de l'attention déclenchée par la perception du regard. Le déplacement attentionnel qui découle de la perception du regard dynamique ou statique module l'activité visuelle après la première étape de traitement sensoriel dans le cortex visuel primaire en facilitant celui-ci. Le regard est donc un indicateur attentionnel particulièrement puissant.(PSY 3)--UCL, 200

Shifts of spatial attention cued by irrelevant numbers: electrophysiological evidence.

The article discusses transpositions of photographs of artists contained in W. Szymborska's works Znieruchomienie [Demotioning], Z. Herbert's Pan Cogito z Marią Rasputin - próba kontaktu [Pan Cogito with Mary Rasputin - an attempt to contact] and A. Stasiuk's Jadąc do Babadag (Going to Babadag). The common feature of these three presentations consists in depriving or levelling the biographical context thanks to which general musings on human nature become possible. They lead to a conclusion on the uprooted character of human condition, which becomes deprived of its home (Stasiuk), mother country and culture (Herbert) and even corporality (Szymborska). Due to this, man appears as an unrecognisable being, possible to capture exclusively in the temporal categories.The article discusses transpositions of photographs of artists contained in W. Szymborska's works Znieruchomienie [Demotioning], Z. Herbert's Pan Cogito z Marią Rasputin - próba kontaktu [Pan Cogito with Mary Rasputin - an attempt to contact] and A. Stasiuk's Jadąc do Babadag (Going to Babadag). The common feature of these three presentations consists in depriving or levelling the biographical context thanks to which general musings on human nature become possible. They lead to a conclusion on the uprooted character of human condition, which becomes deprived of its home (Stasiuk), mother country and culture (Herbert) and even corporality (Szymborska). Due to this, man appears as an unrecognisable being, possible to capture exclusively in the temporal categories

Spatial attention triggered by eye gaze increases and speeds up early visual activity

What are the neuronal correlates of reflexive shifts of attention triggered by eye gaze direction? Event related potentials (ERPs) were measured on 14 subjects performing a spatial attention task where eye gaze direction of a face cued the location of a forthcoming target. Subjects were faster in detecting a validly cued target, i.e. one appearing at the location the eye was gazing at, compared to invalidly cued targets, despite the non-predictive value of the eye cues. ERP results showed an enhanced and earlier occipito-parietal P1 and N1 for valid trials, demonstrating the early modulation of visual input by attentional allocation. These findings provide the first evidence that social attention can rapidly modify the processing of visual information in extrastriate cortex

Spatial attention triggered by eye gaze enhances and speeds up visual processing in upper and lower visual fields beyond early striate visual processing.

OBJECTIVE: The detection of a lateralized visual target is faster when preceded by a face gazing to the location of this stimulus. Here we aimed to clarify the time-course of the visual processing modulated by these reflexive shifts of attention. METHODS: ERPs were measured on 16 subjects performing a speeded location task on a circular checkerboard. The checkerboard target appeared either on the left or right of the upper or lower visual field, and was preceded by a central face orienting its gaze obliquely to one of the four possible corner locations for the target to appear. RESULTS: Congruently cued targets were located faster than incongruently cued targets and were associated with larger and earlier occipital P1 (approximately 110 ms) and occipito-parieto-temporal N1 (approximately 150 ms) components. However, no such attentional modulations were found on the earlier C1 visual component, best observed with a negative polarity for upper visual field stimulations, and thought to originate largely from primary visual cortex. CONCLUSIONS AND SIGNIFICANCE: These results show that reflexive shifts of attention following oblique eye gaze to upper and lower visual fields increase and speed up the processing of visual information beyond the feedforward flow of information in primary visual cortex

Perception of static eye gaze direction facilitates subsequent early visual processing

OBJECTIVE: Using event-related potentials (ERPs), it has been recently shown that a reflexive shift of attention following the observation of a dynamic eye gaze cue enhances and speeds up early visual processing of a target presented at the gazed-at location. Here we investigate whether similar early sensory modulations are also elicited by static gaze cues, or if previously described attentional effects were caused mainly by visual motion cues and not by eye gaze direction per se. Furthermore, we explore if these possible attentional orienting effects reflect facilitation of the processing of cued stimuli, inhibition of the unattended stimuli, or both. METHODS: Subjects were presented with a face looking to the right or left visual field (VF), or straight away, before the occurrence of a lateralized target to detect. There were 3 conditions in this nonpredictive cueing task: (1) target presented in the VF indicated by the eye gaze direction (congruent); (2) opposite to the eye gaze direction (incongruent); or (3) preceded by a straight gazing face (neutral). RESULTS: Subjects were faster at detecting congruently than incongruently and neutrally cued targets. Facilitation effects were observed on early ERP components: the occipital P1 and occipito-temporal N1 components were speeded up as early as approximately 100 ms following stimulus onset (P1), and enhanced (P1 and N1) in response to congruent trials, particularly in the right hemisphere. CONCLUSIONS: Spatial attention triggered by static eye gaze direction produces response facilitations - predominantly lateralized to the right hemisphere - from the early sensory stages of visual processing. Significance: This study provides the first evidence of a speeding up and amplification of early visual processing following attention triggered by static eye gaze perception

Shifts of spatial attention cued by irrelevant numbers: Electrophysiological evidence from a target discrimination task

Fischer et al. demonstrated that a centrally presented number can shift attention to the left/right when its magnitude is small/large. Two electrophysiological studies described these attentional effects as event-related potentials (ERPs) at centro-parietal sites. Since both studies used target detection tasks, it remains currently unknown whether similar results would be obtained with a discrimination task. We used ERPs to test whether digit cues also induce attention shifts when participants perform a feature-discrimination task on targets. ERPs were recorded whereas subjects discriminated the colour of lateral targets that were preceded by a central non-predictive digit. Analysis of cue-locked controlateral vs. ipsilateral ERP activity showed the emergence of early preparatory attention-directing components in parietal and frontal regions. Moreover, target-locked P1 components at occipito-parietal sites were significantly modulated by digit magnitude-target side congruency. These results demonstrate that irrelevant digit cues also bias sensory processing when embedded in a feature-discrimination task