Inferior Temporal Cortex: Columns and Horizontal Axons
IBRO satellite symposium on "Physiology and anatomy of the Association Cortices"
17-20 July 1995, Inuyama, Aichi, Japan
Department of Cognitive Neuroscience, Osaka University Medical School, and PRESTO, Research Development Corporation of Japan, Suita, Osaka 565, Japan.
Evidence for functional columnar organization has been scarce in association
cortices as opposed to the well-established case in the primary visual
cortex. The lack of evidence for columns in association cortices may be
partly because neurons upstream along the cortical hierarchy show highly
integrated response properties, and their stimulus selectivity is difficult
to characterize. The lack of evidence may also be
due to the notion that association cortices are critically involved in dynamic cognitive functions, such as perception. Emphasis on the dynamic aspects of the neuronal network often discourages efforts to find organization such as columns which remain
stable, at least for a certain period of time.
Cytoarchitectonic area TE of the inferior temporal cortex of the macaque monkey is a higher association cortex at or near the final stage of the visual pathway essential to object recognition. Use of a computer graphics system in generation and presentation of visual stimuli has recently made it possible for visual stimulus to be generated and modified on line while activity of a single cell in the TE is monitored, allowing the minimal combination of stimulus features required to activate the cell to be identified. This method has led us to the discovery that the TE consists of columns, each containing cells responding to similar features of objects. In this talk, I shall describe visual response characteristics of TE neurons and physiological aspects of the columnar organization of the TE. Local neuronal circuitry related to these functional columns, particularly the intrinsic horizontal axons, will then be discussed.
Supportcd bygrants from the UeharaMemorial Foundation, the Casio Science Promotion Foundation, and the Ichiro Kanehara Foundation.