Reciprocal Connectivity of Identified Color-Processing Modules in the Monkey Inferior Temporal Cortex

The inferior temporal (IT) cortex is the last unimodal visual area in the ventral visual pathway and is essential for color discrimination. Recent imaging and electrophysiological studies have revealed the presence of several distinct patches of color-selective cells in the anterior IT cortex (AIT) and posterior IT cortex (PIT). To understand the neural machinery for color processing in the IT cortex, in the present study, we combined anatomical tracing methods with electrophysiological unit recordings to investigate the anatomical connections of identified clusters of color-selective cells in monkey IT cortex. We found that a color cluster in AIT received projections from a color cluster in PIT as well as from discrete clusters of cells in other occipitotemporal areas, in the superior temporal sulcus, and in prefrontal and parietal cortices. The distribution of the labeled cells in PIT closely corresponded with that of the physiologically identified color-selective cells in this region. Furthermore, retrograde tracer injections in the posterior color cluster resulted in labeled cells in the anterior cluster. Thus, temporal lobe color-processing modules form a reciprocally interconnected loop within a distributed network.