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Abstract:
Positron Emission Tomography was used to investigate neural
regions engaged in processing constructions unique to signed
languages: classifier predicates in which the position of the hands
in signing space schematically represents spatial relations among
objects. Ten deaf native signers viewed line drawings depicting a
spatial relation between two objects (e.g., a cup on a table) and
were asked to produce either a classifier construction or an ASL
preposition that described the spatial relation or to name the
figure object (colored red). Compared to naming objects, describing
spatial relationships with classifier constructions engaged the
supramarginal gyrus bilaterally and the superior parietal lobule on
the right. Naming spatial relations with ASL prepositions engaged
only the right SMG. Previous research indicates that retrieval of
English prepositions also engages the SMG, but more inferiorly and
primarily on the left. Compared to ASL prepositions, naming spatial
relations with classifier constructions engaged left inferior
temporal cortex -- a region known to be activated when naming
concrete objects in either ASL or English. Left IT may be engaged
because the handshapes in classifier constructions encode
information about object type (e.g., flat surface). Overall, the
results suggest more right hemisphere involvement when expressing
spatial relations in ASL, perhaps because signing space is used to
encode the spatial relationship between objects.
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