Biomedical subjects

Anne-Marie Schuller

Publications and source records attributed to Anne-Marie Schuller.

4 recordsLinked to original sources

PubMed2005

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.

Adult↗

PubMed2004

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.

Adult↗

PubMed2003

Stepwise emergence of the face-sensitive N170 event-related potential component.

The present study used a parametric design to characterize early event-related potentials (ERP) to face stimuli embedded in gradually decreasing random noise levels. For both N170 and the vertex positive potential (VPP) there was a linear increase in amplitude and decrease in latency with decreasing levels of noise. In contrast, the earlier visual P1 component was stable across noise levels. The P1/N170 dissociation suggests not only a functional dissociation between low and high-level visual processing of faces but also that the N170 reflects the integration of sensorial information into a unitary representation. In addition, the N170/VPP association supports the view that they reflect the same processes operating when viewing faces.

Adult↗

PubMed2003

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 processing.

Discrimination, Psychological↗