Visual cortical inputs to deep layers of cat's superior colliculus

Area of Science:

• Neuroscience
• Visual System Research
• Mammalian Neurophysiology

Background:

• The superior colliculi (SC) play a vital role in visual processing and sensorimotor integration.
• The deep layers of the SC receive visual input, but the precise pathways and cortical influences are not fully elucidated.

Purpose of the Study:

• To investigate the role of the visual cortex in relaying retinal information to the deep layers of the superior colliculi in cats.
• To determine the contribution of specific visual cortical areas and retinal Y-cells to SC deep-layer cell activation.

Main Methods:

• Electrical stimulation of the optic pathway and intracortical stimulation of visual areas in anesthetized cats.
• Lesion studies of visual cortical areas (17, 18, 19, PMLS) to assess their necessity for visual input to the SC.
• Analysis of response latencies and activation patterns of deep-layer SC neurons.

Main Results:

• A significant majority of deep-layer SC output cells were driven by optic pathway stimulation, with many showing Y-cell influence.
• Following visual cortex lesions, optic pathway-driven activation and Y-cell influence on deep-layer SC cells were drastically reduced.
• Intracortical stimulation of visual areas activated deep-layer SC cells with latencies consistent with indirect Y-cell pathways, suggesting cortical relay.

Conclusions:

• Visual cortical areas (17, 18, 19, PMLS) are essential for relaying retinal information, particularly Y-cell input, to the deep layers of the superior colliculi.
• Cortical influence on deep SC layers exhibits topographic order, similar to superficial layer projections.
• The visual cortex significantly impacts deep collicular neurons, mediating indirect Y-cell input through direct connections.