Color Selectivity of Neurons in the Posterior Inferior Temporal Cortex of the Macaque Monkey

We recorded the activities of neurons in the lateral surface of the posterior inferior temporal cortex (PIT) of 3 hemispheres of 3 monkeys performing a visual fixation task. We characterized the color and shape selectivities of each neuron, mapped its receptive field (RF), and studied the distributions of these response properties. Using a set of color stimuli that were systematically distributed in Commission Internationale de l'Eclairage-xy chromaticity diagram, we found numerous color-selective neurons distributed throughout the area examined. Neurons in the ventral region tended to have sharper color tuning than those in the dorsal region. We also found a crude retinotopic organization in the ventral region. Within the ventral region of PIT, neurons in the dorsal part had RFs that overlapped the foveal center; the eccentricity of RFs increased in the more ventral part, and neurons in the anterior and posterior parts had RFs that represented the lower and upper visual fields, respectively. In all 3 hemispheres, the region where sharply tuned color-selective neurons were concentrated was confined within this retinotopic map. These findings suggest that PIT is a heterogeneous area and that there is a circumscribed region within it that has crude retinotopic organization and is involved in the processing of color.