Cat lateral suprasylvian cortex: Y-cell inputs and corticotectal projection

Area of Science:

• Neuroscience
• Visual System
• Cortical Processing

Background:

• Retinal Y-cells are known to activate deep superior colliculus layers indirectly through the occipital cortex.
• The lateral suprasylvian area is a potential visual input source to the superior colliculus.
• It remains unclear if Y-cell influences reach the lateral suprasylvian area and if it participates in indirect Y-cell pathways.

Purpose of the Study:

• To investigate retinal influences on the posteromedial lateral suprasylvian area (PMLS) in cats.
• To determine if Y-cell pathways from the retina reach the PMLS.
• To elucidate the role of the PMLS in the indirect Y-cell pathway to the superior colliculus.

Main Methods:

• Recorded single-unit responses in PMLS following electrical stimulation of the optic disk (OD) and optic chiasm (OX).
• Recorded neurons in the dorsal lateral geniculate nucleus (LGNd) antidromically driven from PMLS.
• Analyzed activation latencies to differentiate between direct and indirect retinal inputs.

Main Results:

• Nearly all PMLS cells (99%) showed latency differences indicative of Y-cell axon input.
• A subset of PMLS cells (17%) had short latencies suggesting direct geniculate Y-cell input.
• Most PMLS cells (83%) exhibited longer latencies, indicating multisynaptic Y-cell influence via the LGNd.

Conclusions:

• The PMLS receives visual input from retinal Y-cells through both direct and multisynaptic pathways.
• The PMLS is influenced by Y-cells in the LGNd via a multisynaptic route.
• The PMLS contributes to the indirect Y-cell pathway to the superior colliculus, supporting its role in gaze control.