Effects of hypothermia on cortico-cortical modulation of evoked activity in cat visual cortex

The functional significance of the reciprocal connections between areas 17 and 18 of the cat visual cortex was investigated by the reversible suppression of the activity of cells whose axons project to neighboring cortex. This was accomplished by selectively cooling either area 17 or area 18 in a controlled manner while maintaining the adjacent cortex at normal temperature. Moderate cooling of area 17 in the range from 25° to 28°C produced an enhancement in the surface potentials elicited from the dorsal lateral geniculate nucleus and in the total unit discharge in the adjacent area 18. By cooling area 18 a corresponding effect was produced in the adjacent area 17. A mechanism of inhibitory cortico-cortical loop fibers running between areas 17 and 18 is hypothesized to explain these effects.