The neural origin for asymmetric coding of surface color in the primate visual cortex

Area of Science:

• Neuroscience
• Visual Perception
• Computational Neuroscience

Background:

• End-spectral hues (red and blue) exhibit coding privilege in primate early visual cortex.
• The precise origin of this visual processing bias remains inadequately understood.

Purpose of the Study:

• To elucidate the origin and progression of end-spectral bias within the primate visual system.
• To investigate the neural mechanisms underlying asymmetric color coding from subcortical to cortical areas.

Main Methods:

• Functional magnetic resonance imaging (fMRI) and single-unit electrophysiological recordings in macaques.
• Analysis of visual processing along the ventral pathway (V1 to V4).
• Dynamic causal modeling (DCM) to assess feedforward and recurrent influences.

Main Results:

• Correlated end-spectral biases between the lateral geniculate nucleus (LGN) and V1 suggest a subcortical origin.
• Red bias against green peaked in V1 and decreased along the ventral stream; blue bias against yellow increased.
• The strongest end-spectral bias in V1 was localized to layer 4C.
• DCM revealed both feedforward and recurrent modifications of this bias.

Conclusions:

• End-spectral bias is present in the LGN and transmitted to V1 primarily via the parvocellular pathway.
• Cortical processing further modulates and embellishes this initial subcortical bias.
• Asymmetric color coding originates subcortically and is shaped by subsequent neural computations.