16
NEURAL SPECIALIZATIONS
FOR TONAL PROCESSING
.
Abstract
The processing of pitch, a central aspect of music perception, is neurally dissociable from other per-
ceptual functions. Studies using behavioural-lesion techniques as well as brain imaging methods
demonstrate that tonal processing recruits mechanisms in areas of the right auditory cortex.
Specifically, the right primary auditory area appears to be crucial for fine-grained representation of
pitch information. Processing of pitch patterns, such as occurs in melodies, requires higher-order
cortical areas, and interactions with the frontal cortex. The latter are likely related to tonal working
memory functions that are necessary for the on-line maintenance and encoding of tonal patterns.
One hypothesis that may explain why right-hemisphere auditory cortices seem to be so important to
tonal processing is that left auditory regions are better suited for rapidly changing broad-band stim-
uli, such as speech, whereas the right auditory cortex may be specialized for slower narrow-band
stimuli, such as tonal patterns. Evidence favouring this hypothesis was obtained in a functional imag-
ing study in which spectral and temporal parameters were varied independently. The hypothesis also
receives support from structural studies of the auditory cortex, which indicate that spectral and
temporal processing may depend on interhemispheric differences in grey/white matter distribution
and other anatomical features.
Keywords:Hemispheric functional specialization; Pitch processing; Pitch patterns
How does the nervous system analyze and make sense of information coming from the
environment? This central question in contemporary neuroscience has been addressed
from many perspectives in the last two decades. In the auditory domain, a great deal of
effort has gone into understanding the way in which the human brain processes speech
sounds. Given the importance of speech and spoken language to human communication
and behaviour, this is not surprising. It is interesting, however, to consider other aspects of
auditory information processing that may help to round out the picture. Increasingly,
music is being recognized as an important component of human activity that may help us
to gain insight into the functional organization of the human brain. It may be argued that
the perception, encoding, and reproduction of musical sounds requires neural mechanisms
that are at least as complex as those for speech; indeed, it seems likely that speech and music
must engage the most cognitively demanding aspects of auditory processing. It may further