Biomedical subjects

Corentin Jacques

Publications and source records attributed to Corentin Jacques.

4 recordsLinked to original sources

PubMed2006

Electrophysiological evidence for temporal dissociation between spatial attention and sensory competition during human face processing.

Scalp event-related potential (ERP) studies in humans indicate that face processes taking place between 130 and 170 ms after stimulus onset at posterior sites (N170) are strongly reduced when another face stimulus is processed concurrently or has been presented shortly before for a prolonged period. These observations suggest that neural representations of individual faces compete in the occipitotemporal cortex as early as 130 ms. Here, we tested the respective role of spatial attention and sensory competition in accounting for the amplitude reduction of the N170 during concurrent face stimulation. ERPs time locked to a lateralized face stimulus were recorded while subjects were fixating either a face or a controlled scrambled-face stimulus (context factor) and were engaged in either a high- or a low-attentional load task at fixation (task factor). The N170 amplitude to the lateralized face stimulus was reduced both when the central stimulus was a face compared with a scrambled face and when the attentional load at fixation was high. However, these effects of context and task factors were largely additive. Most importantly, spatial attention modulated visual processes as early as 80 ms after stimulus onset, whereas sensory competition effects started at about 130 ms. These results provide strong evidence that the N170 in response to faces is modulated by spatial attention, and also that spatial attention and sensory competition do not reflect the same mechanisms of early selection of visual information in the extrastriate cortex.

Adult↗

PubMed2006

The time course of visual competition to the presentation of centrally fixated faces.

A recent event-related potential (ERP) study showed that the occipitotemporal component N170 recorded to a face stimulus appearing in the peripheral visual field is strongly reduced when subjects are concurrently fixating another face stimulus. This suggests that concurrently presented face stimuli compete for neural representation in the occipitotemporal cortex between 100 and 200 ms following stimulus onset. We tested whether this competition can be observed for a foveally presented face stimulus appearing next to either two peripheral face pictures or two peripheral control stimuli. The N170 in response to the fixated central face stimulus was substantially reduced (approximately 20% of signal) when it was presented next to peripheral face stimuli. The response suppression was smaller in magnitude than in a previous study where the competing stimulus was fixated and the target stimulus appeared in the periphery. Besides providing a better control for attentional and eye movement confounds, the concurrent stimulation paradigm for fixated face stimuli in ERPs offers a powerful tool to investigate the time course and the nature of the interactions between face and nonface object representations.

Adult↗

PubMed2006

The speed of individual face categorization.

How fast does the human visual system discriminate individual faces? To address this question, we used a continuous-stimulation paradigm in which event-related potentials (ERPs) to a face stimulus are recorded with respect to another face stimulus, rather than to a preceding blank-screen baseline epoch. Following the shift between two face stimuli, posterior sites showed an early negative ERP deflection that started at 130 ms and peaked at 160 ms, the latency of the N170, an ERP component associated with discriminating faces from objects. The ERP we recorded was larger in amplitude when the preceding stimulus was perceived as a different individual face rather than the same individual face, although face pairs were of equal physical distance in the two conditions. These findings provide direct evidence that individual face discrimination in humans can take place as early as 130 ms following stimulus onset, during the same time window as face detection.

Adult↗

PubMed2004

Concurrent processing reveals competition between visual representations of faces.

Scalp electrophysiological recordings in humans indicate that the processing of faces differs from other categories between 100 and 200 ms after stimulus onset, peaking at the N170. To test the effect of the addition of a second face stimulus in the visual field on the face-related N170, we measured this component in response to a laterally presented face stimulus while subjects were processing either a central face or a control stimulus. As early as 130 ms following the lateralized face stimulus, there was a strong (approximately 40% of signal) and specific reduction of the N170 amplitude when subjects were concurrently processing a central face. This observation suggests that the early stages of the N170 reflect the activation of individual faces having overlapping and competing neural representations in the human occipito-temporal cortex.

Adult↗