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Abstract:
Recent neurological and neuroimaging data suggest that
distinct neural systems subserve musical melody, harmony, and
rhythm. To elucidate the neural basis of the perception of rhythm,
we selectively mapped its principal components with PET. Five
non-musicians discriminated pairs of monotonic rhythms with respect
to pattern (phrasing), tempo (increasing or decreasing rate), meter
(3/4, 5/8, etc.), or duration (total time per sequence). Subjects
performed rest and a pitch discrimination control in which a single
note in one of two metronomic melodies could vary in pitch. Stimuli
were adjusted to be highly similar across conditions. Distinct
patterns of activity were detected for each rhythm discrimination,
relative to pitch control (P<.001). Discrimination of meter,
tempo, and pattern, but not duration, strongly activated
cerebellum, as well as inferior colliculus. Strong
condition-specific activations were observed in left medial
superior frontal and anterior cingulate cortex for pattern; in
right frontal cortex (BA 44) for meter; in basal ganglia for tempo;
and in right frontal (BA 10, 47, 6) and posterior cingulate cortex
for duration. Some areas in the observed subsystems likely support
auditory attention and working memory, others are probably involved
in temporal grouping. The strong cerebellar activations, also
detected for pitch discriminations (vs. rest), likely subserve
perceptual/cognitive processing rather than motor activity (which
was absent).
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