?
The contributions of the arcuate fasciculus segments to language processing
The connectivity between perisylvian language areas is subserved by the three segments
of the arcuate fasciculus (AF): long segment, connecting posterior temporal and inferior
frontal areas, and anterior and posterior segments, connecting inferior frontal lobule to
inferior frontal and posterior temporal areas, respectively. Disconnection of the long segment
of the AF gives rise to conduction aphasia, manifesting itself in impaired repetition due to a
deficit in sensorimotor integration. Systematic analyses of the specific contributions of the
three segments of the AF to language processing are, however, lacking. The current study
addresses the roles of these white-matter tracts in language production and comprehension at
various linguistic levels. We found that lower volume of the long AF segment following
neurosurgery is associated with greater deficit in language production and repetition,
consistent with the tract’s well-established role in sensorimotor integration. We did not find
any relation between the volumes of the anterior and posterior AF segments and language
deficits during word and sentence production and comprehension. One plausible explanation
is that these tracts are not critical for language processing, whereas the functions they underlie
in healthy speakers demonstrate a greater capacity for reorganization during the slow growth
of a brain tumor, as opposed to those carried out by the long AF segment.