Poster B137, Sunday, March 26, 8:00 – 10:00 am, Pacific Concourse
Is the N170 lateralization for word and face processing affected by sign language experience and/or deafness?
Zed Sevcikova Sehyr1, Karen Emmorey1, Katherine J. Midgley1, Phillip J. Holcomb1; 1San Diego State University
We examined whether lateralization of N170 to words and faces in deaf signers and hearing speakers differs as a result of distinct perceptual experiences. Left-lateralization of N170 for words is well-established in skilled hearing right-handed readers. The N170 for faces is typically right-lateralized although this finding is less consistent. Early neurophysiological studies suggested greater right hemisphere involvement in word reading for deaf individuals and some fMRI evidence points to leftward asymmetries in language regions for deaf signers viewing linguistic and emotional faces. Twenty-four deaf signers (12 female) and 32 hearing non-signers (17 female) made same-different judgments to pairs of words or faces (192 trials each), where the first stimulus was presented centrally and the second was presented to either the left or right hemisphere. EEG from 29 electrode sites was recorded to the central stimulus and average-referenced. Both groups showed a left-lateralized N170 for words at occipital sites, but only hearing participants also showed a larger N170 at left than right temporal sites. Further, N170 lateralization for words reliably indexed word discrimination accuracy in the hearing but not the deaf group. For faces, both groups showed bilateral N170 at occipitotemporal regions, with only the hearing males trending towards right-lateralized N170. No gender differences in N170 asymmetry were observed in the deaf group. The study offers evidence for unique organization of visual pathways in the occipitotemporal cortex for deaf signers. The asymmetry of N170 to faces may be sensitive to a host of individual factors and requires further scrutiny.
Topic Area: PERCEPTION & ACTION: Vision