Speaker/Affiliation: Josef P. Rauschecker Ph.D.

D.Sc. Professor Department of Physiology and Biophysics Georgetown Unive

rsity Medical Center

When/Location: 3/5/2007 12:00 PM SEA 4.244

Title of Talk: Parallel Processing Streams in Primate Auditory Cortex<

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Reception with Refreshments at 11:30 AM

Abstract: The auditor

y system serves a dual function of identifying and localizing sound sources

. Where in the brain are these functions of hearing implemented? Sound loca

lization has traditionally been assigned to brainstem nuclei. However lesi

ons of auditory cortex in higher mammals including man also cause severe

impairment of sound localization. Neurons in primary auditory cortex (A1) r

espond to tones of a single frequency but also to more complex acoustic sig

nals; in addition they may also be tuned to sound location. Thus A1 seem

s to fulfill all functional requirements of hearing. On the other hand add

itional auditory areas have been identified recently in the belt cortex sur

rounding A1. Why are they needed if A1 together with the brainstem alrea

dy comprises all functions of hearing? The answer is that the complexity of
preferred acoustic stimuli increases in nonprimary auditory cortical areas

. In addition specialized response properties are encountered at a higher

incidence in some areas than in others. Furthermore the anatomical project

ions from each of the belt areas target specific regions in parietal and pr

efrontal cortex that are known to subserve specified functions such as the
processing of space and object information. In humans functional imaging

has made specialized processing streams evident by lighting up cortical are

as that are jointly activated during a specific task such as auditory moti

on processing or the identification of phonemes. I will review the evidence
from both human and nonhuman primates supporting the existence of parallel
processing streams in the auditory cortex specialized for the identificati

on and localization of sounds. In addition we have begun to identify vario

us mechanisms that may be responsible for generating response specificities
in different areas and their organization into computational maps. The pla

sticity of these maps and their reassignment as a consequence of early sens

ory deprivation will also be discussed if time remains.