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Abstract:
Broca's area, traditionally viewed as an expressive language
'center', has been reconsidered more recently as exclusively
involved in syntactic function (1). Using fMRI, we studied 9
right-handed adults during performance on a semantic decision task
(determining whether subsequently presented noun-verb pairs were
semantically associated), alternating in a blocked design with a
visuoperceptual control task (deciding whether subsequent
presentations of strings of the letter "x" [mixed lower- and
uppercase] were identical). In groupwise regression with a
hemodynamic model, we found significant activation during semantic
decision in left inferior frontal and middle temporal regions, the
bilateral superior frontal gyri, and the left amygdala. Our
findings suggest (a) that the role of Broca's area goes beyond
expressive language functions; and (b) that Broca's area is
involved in a purely semantic task and therefore not exclusively
specialized in syntactic functions. The activation cluster in areas
44/45 overlapped with foci previously identified in studies on
syntactic processing (2). We conclude that the left inferior
frontal and middle temporal regions, while playing differential
roles (given specific connectivity with sensorimotor cortices), are
part of a distributed network involved in language processing,
which functions integratively rather than in modular fashion.
(1) Grodzinky Y BBS 23 (2000):1-71
(2) Caplan D et al. Hum Brain Mapp 9 (2000):65-71
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