The cognitive neuroscience of signed language

The present article is an assessment of the current state of knowledge in t he field of cognitive neuroscience of signed language. Reviewed lesion data show that the left hemisphere is dominant for perception and production of signed language in aphasics, in a fashion similar to spoken language aphas ia. Several neuropsychological dissociations support this claim: Nonlinguis tic visuospatial functions can be dissociated from spatial functions and ge neral motor deficits can be dissociated from execution of signs. Reviewed i maging data corroborate the lesion data in that the importance of the left hemisphere is re-confirmed. The data also establish the role of the right h emisphere in signed language processing. Alternative hypotheses regarding w hat aspects of signed language processing are handled by the right hemisphe re are currently tested. The second section of the paper starts by addressi ng the role that early acquisition of signed and spoken language play for t he neurofunctional activation patterns in the brain. Compensatory cognitive and communicative enhancements have also been documented as a function of early sign language use, suggesting an interesting interaction between lang uage and cognition. Recent behavioural data on sign processing in working m emory - a cognitive system important for language perception and production suggest e.g. phonological loop effects analogous to those obtained for spe ech processing. Neuroimaging studies will have to address this potential co mmunality. (C) 2000 Elsevier Science B.V. All rights reserved.