Abstract
Optical imaging of macaque inferior temporal cortex (IT) reveals that an image of a complex object activates several, separated columns of cells, each tuned to an individual type of part or a pair of parts of the object. (Tsunoda et al., Nat. Neuro., 2001). Single unit recordings (Kayaert, et al., 2003, J. Neurosci.; VSS, ′03; ′04) show that cells in IT a) modulate, i.e., change their firing, more to a change in a nonaccidental (NAP) than a metric property (MP), although there is definite sensitivity to MPs, b) show equivalent modulation to changes in MPs as changes in the object's orientation in depth for image differences of equivalent magnitude, c) reveal the greater modulation to NAP than MP changes in 2-part as well as 1-part objects, and in rendered, silhouette, and line drawing versions of these objects, d) are generally tuned to a single generalized-cylinder attribute of a part (e.g, changes in the curvature of the axis or the parallelism of the sides), e) modulate more to differences in simple shapes that can be readily characterized by generalized cylinder attributes than shapes resembling complex textures, f) show invariance to direction of illumination despite large image changes produced by illumination variables. These neural results are highly compatible with psychophysical results with human observers and theories positing object representations in terms of simple parts distinguished by NAPs.
Human Frontiers Science Program Organization RG0035/2000B