musical rhythm. We examined the selective perception of individual principal components
of musical rhythm—that is, pattern (phrasing), tempo, meter, and duration. In addition, in
order to explore the effect of musical talent and training on the neural systems supporting
musical rhythm perception, expert musicians were compared to nonmusicians.
Studies of brain-damaged patients have reported that the perception of rhythm can be
impaired without affecting melodic processing, suggesting that there is a distinct neural
system for the representation of rhythm.^61 Some studies have been in-conclusive as to
whether rhythm was a left hemispheric or bilateral neural process.62,63Interestingly, recent
fMRI data suggest that memory for familiar, regular rhythms (with whole-number inter-
val ratios) is supported by left frontal (BA 6) and parietal cortex and right anterior cere-
bellum.^48 On the other hand, these data suggested that memory for more unfamiliar
rhythms (with fractionated interval ratios) was supported by right prefrontal, frontal (BA
6), and parietal areas, along with bilateral posterior cerebellum.
The involvement of the cerebellum in the processing of musical rhythm is consistent
with data from our second PET study (see earlier) and those of two other studies.10,42This
implication is congruent with neurological findings that cerebellar patients are impaired at
the fine perception of temporal features of auditory stimuli.^47
Involvement of parietal and prefrontal cortex in rhythm processing^48 is also consistent
with data from our second PET study. In addition, this activity is congruent with recent
neurological data implicating an inferior parietal-prefrontal circuit that supports time-
dependent attention and working memory functions necessary for perception of duration
of auditory stimuli.^64 Of particular note in this context is a study of unilateral temporal
corticectomy patients in which evidence was found for a dissociation between the areas
processing meter as opposed to rhythm pattern, with anterior superior temporal areas
implicated for meter.^11
In the present study, Michael Thaut and I explored the principal components of rhythm:
duration, pattern, tempo (dynamically increasing or decreasing rate), and meter (e.g. the
differing periodicities of 3/4, 4/4, 5/4, 5/8, 7/8, and 9/8). Using the same PET methods as in
our preceding studies, we imaged nonmusicians and musicians, making covert discrimina-
tions of pairs of rhythmic auditory patterns. Each scanned set of trials required the subject
to focus on a single one of four principal components of rhythm. We also included a pitch
discrimination control task in which subjects compared pairs of auditory sequences. In the
pitch discrimination task it was possible for a single note to vary in pitch in one member
of the stimulus pair. The pitch discrimination stimuli possessed a metronomic rhythm (i.e.
all notes had the same duration). As a control task, the pitch stimuli required comparable
auditory perception, working memory, and comparison and decision processes as the
rhythm tasks, without requiring the processing of rhythmic features of duration, meter,
tempo, or pattern.
Participating in the study were five musicians, with (at least) an undergraduate univer-
sity degree in music, and five nonmusicians, with no music training or performance experi-
ence beyond childhood. All 10 subjects were right-handed adult males. The stimuli (apart
from the pitch control) were always 440-Hz computer-generated piano timbre sounds of
231- or 462-ms duration. The interval between tones in a stimulus sequence was a multi-
ple of 231 ms. The stimuli on the duration, pattern, and pitch control trials were modeled
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