Tuning face perception with electrical stimulation of the fusiform gyrus

Abstract

The fusiform gyrus (FG) is an important node in the face processing network, but knowledge of its causal role in face perception is currently limited. Recent work demonstrated that high frequency stimulation applied to the FG distorts the perception of faces in human subjects (Parvizi, et al., 2012). However, the timing of this process in the FG relative to stimulus onset and the spatial extent of FG's role in face perception are unknown. Here, we investigate the causal role of the FG in face perception by applying precise, event-related electrical stimulation to higher order visual areas including the FG in six human subjects undergoing intracranial monitoring for epilepsy. We compared the effects of single brief (100μs) electrical pulses to the FG and non-face-selective visual areas on the speed and accuracy of detecting distorted faces. Brief electrical stimulation applied to face-selective sites did not affect accuracy but significantly increased the reaction time (RT) of detecting face distortions. Importantly, RT was altered only when electrical stimulation was applied 100ms after visual onset and in face-selective but not place-selective sites. Furthermore, electrical stimulation applied to face-selective areas decreased the amplitude of visual evoked potentials and high gamma power over this time window. Together, these results suggest that electrical stimulation of face-selective regions within a critical time window induces a delay in face perception. These findings support a temporally and spatially specific causal role of face-selective areas and signify an important link between electrophysiology and behavior in face perception.

The right hemispheric dominance for face perception in preschool children depends on the visual discrimination level

“…As presented in the introduction, the right hemispheric dominance for individual face discrimination but not for generic face categorization in preschool children is in line with a variety of observations made in adults, showing either enhanced or exclusive right lateralization when individuating faces as compared to the categorization of faces as faces. This is the case for EEG measures, either obtained in standard ERP paradigms (e.g., Jacques & Rossion, ) or during FPVS (Liu‐Shuang et al, ; Rossion et al, ) and, most importantly, when considering the interruption of function either following brain damage (e.g., Rossion et al, ), transcranial magnetic stimulation over the right lateral occipital cortex (Ambrus et al, ; Pitcher et al, ; Solomon‐Harris et al, ) or intracranial stimulation in the right inferior occipital gyrus and fusiform gyrus (Chong et al, ; Jonas et al, , ; Keller et al, ).…”

“…Likewise, transcranial magnetic stimulation over the right lateral occipital cortex impairs individuation of faces (Ambrus, Dotzer, Schweinberger, & Kovács, ; Pitcher, Walsh, Yovel, & Duchaine, ; Solomon‐Harris, Mullin, & Steeves, ) but not the categorization of a face as a face (Solomon‐Harris et al, ). In the same vein, transient failures to individuate faces have been observed following intracranial stimulation in the right but not the left face‐selective regions (Jonas et al, , ), while difficulties at categorizing visual stimuli as faces can be observed following stimulation in either the left or right hemisphere face‐selective regions (Chong et al, ; Keller et al, ). In EEG studies, indexes of individual face discrimination usually found using stimulus repetition are strongly right lateralized, whether they are obtained in standard ERP designs (i.e., on the N170, Jacques & Rossion, ; Rossion, ) or with EEG frequency‐tagging (Liu‐Shuang, Norcia, & Rossion, ; Rossion & Boremanse, ).…”

Intracortical dynamics underlying repetitive stimulation predicts changes in network connectivity

“…changes in brain excitability at baseline and after stimulation, we performed corticocortical evoked potential (CCEP) mapping 27 . CCEPs have been used to predict the onset of ictal events 28 , examine the functional brain infrastructure 29,30,31,32 , and causally examine the fronto-parietal 33 , hippocampal 34,35 , visual 36 , and language 37 networks. Prior to and immediately after repetitive stimulation, we applied bipolar electrical stimulation (biphasic pulses at 100 µs/phase) with a 1s inter-stimulation interval (ISI).…”

Mapping face categorization in the human ventral occipitotemporal cortex with direct neural intracranial recordings

“…described facial hallucinations (isolated eyes, single or multiple faces), without looking at faces, following stimulation of distributed face‐selective sites along the posteroanterior axis of the VOTC. More recent ECoG studies have focused on the latFG, reporting facial perceptual distortions in the right but not in the left hemisphere, or deficits in face categorization …”