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Abstract:
Broca's area in the left inferior frontal gyrus, whose
central components are the cytoarchitectonically defined Brodmann
areas (BA) 44 and 45, plays a critical role in language production.
Amunts et al. (J. Comp. Neurol., 1999) performed histological
analysis on 10 human brains to map BA44 and BA45 in each
individual, and constructed a probabilistic atlas in Talairach
space for these two areas. We divided each area into core and
peripheral subregions (core - voxels identified in the majority of
brains as belonging to the particular Brodmann area) and combined
this atlas with PET data obtained from proficient bilingual adults,
whose parents were deaf, while they produced spontaneous narratives
using speech and ASL during separate scans. Each type of narrative
was compared to an appropriate sensorimotor control task lacking
linguistic content. The core portions of BA44 and BA45 were
activated by both speech and ASL, and by the sensorimotor tasks
(relative to a rest condition). Neither core area showed any
significant difference in PET activity when speech and ASL were
contrasted, although peripheral BA44 was more active during speech
than ASL. These results indicate that BA44 and BA45 can be
activated by non-language tasks, and that similar neural substrates
in BA44 and BA45 are used for ASL and speech.
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