Structure and Function
THE INFERIOR TEMPORAL
CORTEX: COLOUNS AND HORIZONTAL AXONS
Department of Cognitive Neuroscience, Osaka University Medical School,
Yamadaoka 2-2, Suita, Osaka 565, Japan.
The functional architecture of the TE of the monkey inferior temporal cortex is beginning to be elucidated. Neurons in the TE do not signal abstract representation of an object, but convey information only on component features of objects. The TE shares the two important organizational features with the primary visual cortex: columns and horizontal axons. A straightforward interpretation of columnar organization in the TE is that columns represent a few hundred component object features, and the combination of active columns may signal the whole configuration of an object. The principle of combination enables the TE to represent a huge number of objects despite a small number of columns, in a manner similar to the 26 letters in the English alphabet producing a large number of words (“visual alphabet hypothesis”; Fujita, 1993). The existence of horizontal axons, however, suggests that an object does not simply activate multiple columns in a parallel and noninteractive manner, but that activated columns modulate activities of other columns. It is not known what information horizontal axons carry, how and where columns with different stimulus selectivities interact, or how TE neurons respond to a combination of different features. These are among the key future questions to be addressed to advance our understanding of how columns in the TE function.