Columns for complex visual object features in the inferotemporal cortex: clustering of cells with similar but slightly different stimulus selectivities.

Cells in the inferotemporal cortex (area TE) selectively respond to complex visual object features and those that respond to similar features cluster in a columnar region elongated vertical to the cortical surface. What are the functional roles of the column structure in the inferotemporal cortex? Selectivity of cells within a column is similar but not identical. If we emphasize the similarity among cells within a column, we can regard the columns as units for description of object features. The variety of stimulus selectivity in a column may work as a tool to disregard subtle changes in input images when the system is directed to invariant recognition. Alternatively, if we emphasize the differences in selectivity of cells within a column, the columns can be compared to differential amplifiers, each of which represents variety within a group of features. The enormous number of objects present in nature can be efficiently described by combining outputs of the multiple differential amplifiers in the inferotemporal cortex. The two modes may work in parallel, with a graded balance changing according to the behavioral context. Determining whether or not these hypotheses are valid will require further studies.