Color architecture in alert macaque cortex revealed by FMRI

Area of Science:

• Neuroscience
• Primate Vision
• Functional Neuroimaging

Background:

• The precise neural underpinnings of primate color vision remain incompletely understood.
• Distinguishing color processing from luminance processing in the brain is a key challenge.

Purpose of the Study:

• To map whole-brain color processing in the alert macaque using functional magnetic resonance imaging (fMRI).
• To identify brain regions with color-biased, luminance-biased, and color-afterimage activity.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was employed in alert macaques.
• Analysis focused on identifying differential brain activity related to color versus luminance stimuli.

Main Results:

• Color-biased activity was predominantly observed in ventral stream areas: V1, V2, and parts of V4.
• Luminance bias was found in dorsal stream areas (V3a, MT).
• A distinct region, PITd, on the superior temporal sulcus, showed both color-biased and color-afterimage activity.

Conclusions:

• Color vision in macaques relies on a ventral stream pathway including V1, V2, V4, and PITd.
• The findings suggest PITd is a distinct area involved in color processing, separate from V4 and TEO.
• Integration of fMRI, single-unit, and lesion studies supports a connected ventral pathway for color perception.