Specific and columnar projection from area TEO to TE in the macaque inferotemporal cortex.

The organization of connections from area TEO to TE was studied by the use of the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA-L). Single or, in one case, two small injections of the tracer were made in the lateral part of TEO. Labeled terminals were found in restricted regions of TE within two to five dense foci. In these foci, terminals were distributed beyond the middle layers to form a columnar cluster elongated vertical to the cortical surface. This specificity of connections may derive from an organization that is feature specific rather than retinotopic. Single axons reconstructed from the columnar foci showed heterogeneous features in the laminar distribution. Arbors of some axons were localized in the superficial layers, and those of other were in the middle layers.