Bruno Rossion’s research while affiliated with French National Centre for Scientific Research and other places

Fast periodic visual stimulation (FPVS) allows the objective measurement of brain responses of human word discrimination (i.e., reproducible word-category-selective responses) with a high signal-to-noise ratio. This approach has been successfully employed over the last decade in a number of scalp electroencephalography (EEG) studies. Three important advances for research on word-selective brain responses were achieved in the present study: (1) we extend previous evidence of robust word-category-selective responses to the English language, (2) report results for combined EEG and MEG signals, and (3) source estimation results. English words were presented periodically (2 Hz) among different types of letter strings (10Hz; consonant strings, non-words, pseudowords) whilst recording simultaneous EEG and MEG in 25 participants who performed a simple non-linguistic color detection task. Data were analyzed in sensor and in source space. With only 4 minutes of stimulation we observed a robust word discrimination response in each condition, even when words were embedded in sequences of word-like pseudowords. This response was larger in nonwords and largest in consonant strings. We observed left-lateralized responses in all conditions in the majority of our participants. Cluster-based permutation tests revealed that these responses were left-lateralized in sensor as well as in source space, with peaks in left posterior regions. Our results demonstrate that the FPVS approach can elicit robust English word-discrimination responses in EEG and MEG within only a few minutes of recording time. Together with source estimation, this can provide novel insights into the neural basis of visual word recognition in healthy and clinical populations.

The neural basis of human face recognition has been extensively studied for decades. The contribution of several face-selective brain regions in the ventral occipito-temporal cortex (VOTC; e.g., in the fusiform gyrus, FG; inferior occipital gyrus, IOG) has been established, but the functional organization of this cortical network remains largely unknown. In rare epileptic patients implanted with intracerebral electrodes in several face-selective VOTC regions, an original combination of frequency-tagging and direct electrical stimulation (DES) can provide unique information to address this issue. These depth electrodes allow us to stimulate a local node of the network while recording the functional activity of other implanted regions, with high spatial and temporal resolution. Here we report the case of a 34-year-old man, presented with 70-second sequences of natural images (objects with one face inserted every five images, at a 6Hz rate), while focal stimulation (1,0mA at 55Hz) was separately applied for 10s to four independently defined face-selective areas in the right and left VOTC (right and left lateral FG, right IOG, right anterior FG). Upon stimulation, face-selective neural activity was reduced or abolished both locally and at remote bilateral VOTC recording sites. These remote effects of DES were found in both postero-anterior (i.e., DES to lateral occipital cortex affecting fusiform face-selective activity) and antero-posterior (DES to fusiform gyrus affecting lateral occipital cortex activity) directions as well as across face-selective sites of homologous regions of the two hemispheres. Most importantly, this reduction was extremely specific to the face-selective response, as it did not extend to the general visual response (i.e., 6Hz and harmonics). Overall, these results shed original light on the functional connectivity of the human cortical face recognition network and pave the way for a more widespread and systematic development of this approach to reveal the functional and effective connectivity of human brain networks.

A major scientific objective of cognitive neuroscience is to define cortico-cortical functional connections supporting cognitive functions. Here, we use an original approach combining frequency-tagging and direct electrical stimulation (DES) to test for bidirectional and cross-hemispheric category-specific modulations within the human cortical face network. A unique patient bilaterally implanted with depth electrodes in multiple face-selective cortical regions of the ventral occipito-temporal cortex (VOTC) was shown 70 s sequences of variable natural object images at a 6 Hz rate, objectively identifying deviant face-selective neural activity at 1.2 Hz (i.e., every five images). Concurrent electrical stimulation was separately applied for 10 seconds on four independently defined face-selective sites in the right and left VOTC. Upon stimulation, we observed reduced or even abolished face-selective neural activity locally and, most interestingly, at distant VOTC recording sites. Remote DES effects were found up to the anterior temporal lobe (ATL) in both forward and backward directions along the VOTC, as well as across the two hemispheres. This reduction was specific to face-selective neural activity, with the general 6 Hz visual response being mostly unaffected. Overall, these results shed light on the functional connectivity of the cortical face-selective network, supporting its non-hierarchical organization as well as bidirectional effective category-selective connections between posterior ‘core’ regions and the ATL. They also pave the way for widespread and systematic development of this approach to better understand the functional and effective connectivity of human brain networks.

Fast periodic visual stimulation (FPVS) allows the recording of objective brain responses of human word discrimination (i.e., reproducible word-category-selective responses) with a high signal-to-noise ratio. This approach has been successfully employed over the last decade in a number of scalp electroencephalography (EEG) studies. Three important advances were achieved in this study: (1) robust measures of written word-selective responses with this approach have not been reported in English; (2) responses have only been reported in EEG but not with MEG, and (3) without source localization. Thus, we presented English words periodically (2 Hz) among different types of letter strings (10Hz; consonant strings, non-words, pseudowords) whilst recording simultaneous EEG and MEG in 25 participants who performed a simple non-linguistic color detection task. Data were analyzed in sensor and in source space (L2-minimum-norm estimation, MNE). With only 4 minutes of stimulation we observed a robust word discrimination response in each condition including, importantly, even when words were embedded in word-like pseudowords. This response was larger in nonwords and largest in consonant strings. We observed left-lateralized responses in all conditions in the majority of our participants. Cluster-based permutation tests revealed that these responses were left-lateralized in sensor as well as in source space, with peaks in left posterior regions. Our results demonstrate that the FPVS paradigm can elicit robust English word-discrimination responses in EEG and MEG within only a few minutes of recording time. Together with source estimation, this can provide novel insights into the neural basis of visual word recognition in healthy and clinical populations.

During infancy, intersensory facilitation declines gradually as unisensory perception develops. However, this trade‐off was mainly investigated using audiovisual stimulations. Here, fifty 4‐ to 12‐month‐old infants (26 females, predominately White) were tested in 2017–2020 to determine whether the facilitating effect of their mother's body odor on neural face categorization, as previously observed at 4 months, decreases with age. In a baseline odor context, the results revealed a face‐selective electroencephalographic response that increases and changes qualitatively between 4 and 12 months, marking improved face categorization. At the same time, the benefit of adding maternal odor fades with age ( R ² = .31), indicating an inverse relation with the amplitude of the visual response, and generalizing to olfactory‐visual interactions previous evidence from the audiovisual domain.