The comparison of listening to melodies minus noise permits examination of the cerebral
regions specifically active during processing of novel melodies. The principal result indi-
cated a significant CBF increase in the right superior temporal gyrus, anterior to the primary
auditory cortex; a weaker CBF increase was also observed in the left STG. A reanalysis of
these data with a smaller reconstruction filter and improved image registration^22 indicates
that the right STG activation is in the ventrolateral aspect of the gyrus (Figure 16.4). These
findings point to differential activation of primary vs secondary auditory areas within the
STG, depending on the stimulus features. Caution must still be exercised in interpreting the
results, for the noise bursts clearly differ from the melodies on a number of dimensions
(e.g. periodicity, frequency modulation, and spectral composition). It remains to be estab-
lished, therefore, which specific features of the melodies may lead to the observed pattern of238 Figure 16.4Selected PET CBF activation sites associated with processing of tonal melodies. The figures show
averaged PET subtraction images superimposed on a corresponding section of an average anatomical MRI. (To p)
Horizontal, coronal, and sagittal views through a focus located in the right superior temporal gyrus representing a
significant blood flow increase while subjects listened to a series of short, unfamiliar tonal melodies, as compared
with a baseline condition in which they listened to noise bursts that were acoustically equated to the melodies. Also
visible in the horizontal section is a region of significant activity in the left temporal cortex. (Bottom) Horizontal,
coronal, and sagittal views through a focus in the right frontal/opercular region showing activity associated with
making judgements about the pitch of the first and last notes of the tonal sequences as compared to making judge-
ments about the first two notes. Data reanalysed from Zatorre et al.^21 (See Plate 5 in colour section.)