Retrograde Optogenetics Reveals Functional Convergence within a Corticotectal Pathway of Non-Human Primates

Retrograde optogenetics enables tagging and manipulation of pathway-defined neurons, although its application to the non-human primate brain remains challenging. We applied the technique to identify, record, and activate neurons forming the frontal eye field-superior colliculus projection in behaving macaques. Optical stimulation evoked robust contralateral saccades and pathway-selective opto-tagging revealed the functional visuo-motor convergences within this pathway. Our findings resolve a longstanding controversy about the frontal oculomotor outputs and highlight retrograde optogenetics as a powerful tool for primate circuit-level studies.