Abstract
Deaf individuals often display enhanced visual processing abilities, particularly for peripheral motion. Deaf individuals are also more accurate at face discrimination, however this has only been examined in the central visual field. Our aim is to determine whether these face processing enhancements extend to the periphery, and whether they are also reflected in the neuro-physiological responses. Face stimuli were created by morphing between original faces and their anti-face in 1% steps. In a face matching task, subjects were presented with a ‘target’ face and after a delay were required to identify which of two ‘test’ faces matched the target. Test faces appeared either centrally (3.4° from fixation) or peripherally (10°). In an EEG task, a steady-state visual evoked potential (SSVEP) oddball paradigm was used, in which facial images were presented at a base frequency (6 Hz) and within the sequence a different ‘oddball’ face was presented at a lower frequency (1.2 Hz). The similarity between base and oddball images was varied, and were again presented either centrally or peripherally. Behaviorally, there was no difference between subject groups in the central field, however in the periphery, deaf subjects performed significantly better than hearing subjects. This difference was not reflected in the EEG results, with both groups showing similar reductions in oddball amplitudes for faces that were more similar. Furthermore, deaf subjects showed larger decreases in overall amplitudes when images were presented in the periphery. Our behavioral results show that deaf individuals’ enhanced face processing abilities may be more pronounced in the periphery. The discrepancy between the behavioral and EEG results suggest that the face discrimination task and SSVEP oddball reflect different aspects of face processing, with the former perhaps involving more feature-based processing and the latter being more holistic.
Acknowledgement: This work was supported by grants from the National Institutes of Health (EY-023268 to FJ, EY-10834 to MW), with further support for core facilities provided by COBRE P20 GM103650