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View looking down
on the dorsal surface of the STG. Rostral is at bottom, caudal at top,
medial to the left, and lateral to the right. HG, Heschls' Gyrus; PT,
Planum Temporale.
The goal of the present study was to determine whether
the architectonic criteria used to identify the core, lateral belt and
parabelt auditory cortices in macaque monkeys (Macaca fascicularis) could
be used to identify homologous regions in humans (Homo sapiens). Current
evidence indicates that auditory cortex in humans, as in monkeys, is located
on the superior temporal gyrus (STG), and is functionally and structurally
altered in illnesses such as schizophrenia and Alzheimer disease. In this
study, we used serial sets of adjacent sections processed for Nissl substance,
acetylcholinesterase, and parvalbumin to identify the distinguishing cyto-
and chemoarchitectonic features of the core, lateral belt and parabelt
in monkey. These criteria were evaluated in postmortem tissue from a human
subject, leading to the identification of additional criteria specific
to human. The criteria were validated in an additional set of 8 human
subjects. Regions were delineated and their volumes estimated using the
Cavalieri method in these subjects, and the sources of methodologic contribution
to variability of the estimates was assessed. Serial reconstructions of
the auditory cortex in humans were made showing the location of the lateral
belt and parabelt with respect to gross anatomical landmarks. The summary
diagram shown at left depicts the borders of the left auditory core, lateral
belt, internal parabelt, and external parabelt, and the location of area
Tpt, in human brain. Architectonic criteria for the core, lateral belt,
and parabelt were readily adapted from monkey to human. Additionally,
we found evidence for an architectonic subdivision within the parabelt,
present in both species. Variability of regional volume estimates was
readily constrained using a multifaceted approach to reduce potential
sources of variability in regional delineation. These findings provide
the foundation for unbiased quantitative studies of alterations in the
circuitry of the STG in schizophrenia. |