Naturalistic movies and encoding analysis define areal borders in marmoset third-tier visual cortex

Area of Science:

• Neuroscience
• Visual System Research
• Primate Brain Mapping

Background:

• Defining cortical visual area boundaries is crucial for understanding perception.
• Existing methods for boundary definition face limitations in resolution, coverage, and objective analysis, leading to ambiguity.
• The third-tier visual cortex in primates has particularly controversial areal boundaries.

Purpose of the Study:

• To present a novel, objective approach for defining areal boundaries in the primate extrastriate cortex.
• To test conflicting hypotheses regarding the organization of the third-tier visual cortex.
• To clarify controversial areal boundaries using advanced imaging and computational analysis.

Main Methods:

• Combined widefield optical imaging with naturalistic movie stimuli.
• Utilized encoding model analysis for objective boundary definition.
• Validated findings with high-density electrophysiological recordings using Neuropixels probes.

Main Results:

• Demonstrated pronounced tuning preferences within the third-tier visual areas.
• Revealed a specific organizational structure where the dorsomedial area (DM) represents both upper and lower contralateral visual quadrants.
• Confirmed the location of DM immediately anterior to visual area V2.

Conclusions:

• The novel encoding-model approach provides a powerful and objective method to resolve ambiguity in defining visual cortical areal boundaries.
• The study clarifies the controversial organization of the third-tier visual cortex, providing a refined map.
• Findings contribute to a better understanding of visual processing and cortical organization in primates.