Introduction: As a result of permanent sensory deprivation, neural systems that are deprived of their typical input, as well as spared sensory modalities, often reorganize (cross-modal and intramodal plasticity, respectively). In congenitally deaf signers the study of face processing has revealed both cross-modal and intramodal adaptations: the activation of auditory cortices (e.g. superior temporal sulcus) was observed in response to face stimuli (e.g. Benetti et al., 2017); hemispheric dominance shifts in ventral visual areas (e.g. fusiform gyrus) were found in response to the presentation of emotional facial expression (e.g. McCullough et al., 2005). However, a systematic assessment of different stages of face processing in congenitally deaf signers is lacking.Methods: To address this issue, we combined fast periodic visual stimulation with electroencephalography (EEG), an approach providing sensitive and objective measures of face-processing in hearing individuals (e.g., Rossion, 2014). A series of three EEG experiments designed to hierarchically test different levels of face-related discrimination were run in a group of congenitally deaf signers (N=14) and a group of matched controls (N=14). We investigated the following face processing functions: (1) generic face categorization (faces appearing at afixed frequency of 1.2 Hz in a train of visual images of objects appearing at 6 Hz); and in two orthogonally implemented experiments, (2) individual face discrimination (different vs. identical unfamiliar faces, across emotional facial expressions) and (3) facial emotional-expression discrimination (emotional face expressions vs. neutral faces, across identities).Results: In all three experiments, both groups showed bilateral occipito-temporal responses over the scalp. For both generic face categorizationand facial expression discrimination, matched controls displayed, as expected, a right lateralized topography (on average). On the contrary, congenitally deaf individuals showed a left hemispheric dominance. No group difference in hemispheric lateralization emerged instead for individual face discrimination. However, in this latter experiment, congenitally deaf signers exhibited a greater response as compared to matched controls, over the midline, at frontal and central electrode sites. Such a topography pattern is compatible with a cross-modal activation of auditory cortices in congenitally deaf signers.Conclusion: Altogether, our results suggest compensatory changes at distinctive levels of the face-processing system in congenitally deaf signers. The left hemispheric dominance in congenitally deaf signers has often been linked to the relevant role of faces in sign language (e.g. McCullough et al., 2005; Neville et al., 1987)
Face processing in congenitally deaf signers as revealed by fast periodic visual stimulation
Bednaya, Evgenia;Bottari, D.;Pietrini, P.;Ricciardi, E.;
2018-01-01
Abstract
Introduction: As a result of permanent sensory deprivation, neural systems that are deprived of their typical input, as well as spared sensory modalities, often reorganize (cross-modal and intramodal plasticity, respectively). In congenitally deaf signers the study of face processing has revealed both cross-modal and intramodal adaptations: the activation of auditory cortices (e.g. superior temporal sulcus) was observed in response to face stimuli (e.g. Benetti et al., 2017); hemispheric dominance shifts in ventral visual areas (e.g. fusiform gyrus) were found in response to the presentation of emotional facial expression (e.g. McCullough et al., 2005). However, a systematic assessment of different stages of face processing in congenitally deaf signers is lacking.Methods: To address this issue, we combined fast periodic visual stimulation with electroencephalography (EEG), an approach providing sensitive and objective measures of face-processing in hearing individuals (e.g., Rossion, 2014). A series of three EEG experiments designed to hierarchically test different levels of face-related discrimination were run in a group of congenitally deaf signers (N=14) and a group of matched controls (N=14). We investigated the following face processing functions: (1) generic face categorization (faces appearing at afixed frequency of 1.2 Hz in a train of visual images of objects appearing at 6 Hz); and in two orthogonally implemented experiments, (2) individual face discrimination (different vs. identical unfamiliar faces, across emotional facial expressions) and (3) facial emotional-expression discrimination (emotional face expressions vs. neutral faces, across identities).Results: In all three experiments, both groups showed bilateral occipito-temporal responses over the scalp. For both generic face categorizationand facial expression discrimination, matched controls displayed, as expected, a right lateralized topography (on average). On the contrary, congenitally deaf individuals showed a left hemispheric dominance. No group difference in hemispheric lateralization emerged instead for individual face discrimination. However, in this latter experiment, congenitally deaf signers exhibited a greater response as compared to matched controls, over the midline, at frontal and central electrode sites. Such a topography pattern is compatible with a cross-modal activation of auditory cortices in congenitally deaf signers.Conclusion: Altogether, our results suggest compensatory changes at distinctive levels of the face-processing system in congenitally deaf signers. The left hemispheric dominance in congenitally deaf signers has often been linked to the relevant role of faces in sign language (e.g. McCullough et al., 2005; Neville et al., 1987)I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
