10
INTRACEREBRAL EVOKED
POTENTIALS IN PITCH
PERCEPTION REVEAL A
FUNCTIONAL ASYMMETRY
OF HUMAN AUDITORY
CORTEX
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Abstract
One acoustic feature that plays an important role in pitch perception is frequency. Studies on the pro-
cessing of frequency in the human and animal brain have shown that the auditory cortex is tono-
topically organized: low frequencies are represented laterally whereas high frequencies are
represented medially. To date, the study of the functional organization of the human auditory cortex
in the processing of frequency has been limited to the use of either scalp-recorded auditory evoked
potentials (AEPs), which have relatively poor spatial resolving power, or functional imagery tech-
niques, which have poor temporal resolving power. The present study uses intracerebrally recorded
AEPs to explore this topic in the primary and secondary auditory cortices of both hemispheres of the
human brain. Recordings were carried out in 45 adult patients with drug-resistant partial seizures. In
the right hemisphere, clear spectrally organized tonotopic maps were observed with distinct separa-
tions between different frequency-processing regions. AEPs for high frequencies were recorded medi-
ally, whereas AEPs for low frequencies were recorded laterally. In the left hemisphere, however, this
tonotopic organization was less evident, with different regions involved in the processing of a range
of frequencies. The hemisphere-related difference in the processing of tonal frequency is discussed in
relation to pitch perception.
Keywords:Pitch perception; Auditory cortex; Neural processing
The ability to process pitch is of major importance to music and language perception.
Although the acoustic cues necessary to the perception of pitch are mainly of a temporal
nature, human subjects describe pitch as having a spatial dimension (i.e. musical scale).
Traditionally, the literature on the processing of pitch in the human brain has been