plausible to hypothesize that it would also be important for such temporal processing
in music.
Temporal processing in musical sequences
Parallel to the previously reported studies using simple auditory sequences, several studies
investigated temporal processes in musical sequences. It has been suggested that temporal
processing, of which musical rhythm would be an example, is best performed by the func-
tions of the dominant left hemisphere. However, the evidence reported in the literature
provide little support for this hypothesis. Few studies investigating the perception of
dichotically presented stimuli in normal listeners usually report a right ear advantage
which is supposed to reflect left-hemisphere predominance for the perception of tempor-
ally complex nonspeech stimuli,13–16but this perceptual asymmetry has not always been
obtained.^17 Similarly, studies carried out in brain damaged subjects have not systematically
documented a deficit in rhythmic tasks in the presence of a left-hemisphere lesion.
Although evidence supporting left-hemisphere involvement in rhythm have been reported
in a few studies carried out in unilateral brain damaged subjects,18,19other studies have
demonstrated the contribution of right-hemisphere structures and/or a bilateral cerebral
involvement in rhythm discrimination.20–25Two studies have even failed to report deficits
in rhythm discrimination after unilateral temporal lobe resection.11,26However, the use of
musical stimuli for which familiarity and rhythmical complexity are extremely variable
make the comparison between studies difficult. Based on these seemingly contradictory
results obtained in lesion studies, it seems impossible to conclude that left-hemisphere
structures are predominantly involved in musical rhythm.
One functional neuroimaging study investigated the temporal processing of musical pat-
terns^27 but interpretation of the results in this study is made difficult because of method-
ological factors. Using Positron Emission Tomography in normal subjects, an increase of
cerebral blood flow was obtained in left inferior Broca’s area and in left insula when rhythmic
and pitch judgement conditions were compared. Although this finding was interpreted by the
authors as evidence supporting left-hemisphere superiority for temporal processing, it seems
impossible to attribute these foci of activation to a purely temporal processing. Indeed, many
other nontemporal aspects related to the task demands and to the stimuli, that differ between
the two compared conditions, might have contributed to these metabolic changes.
In cognitive psychology, it has been proposed that the perception of rhythmic grouping,
consisting of a sequential organization of relative durations of tones and silent intervals,
should be differentiated from the perception of metre, referring to the underlying perceived
beat marking off equal duration units.28–31Neuropsychological studies have demonstrated
a dissociation between these two components involved in subjective organization of tem-
poral patterns,23,26,32but this dissociation has not been systematically observed.^20 Moreover,
no indication in favour of a lateralized deficit in metrical processing has been reported.
Based on this review, we can assume that the left-dominant hemisphere and more specif-
ically the temporal lobe plays an important role in the processing of simple auditory
sequences requiring rapid timing variations ranging from 10 to 100 ms. However, this left-
hemisphere superiority has not been consistently demonstrated in studies using musical
sequences. Although precise timing information is not usually reported in such studies, the
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