[Source of light-evoked cortical activity after destruction of the main visual pathway]

Electrical responses to flashes and single electrical stimuli applied to optical nerve were recorded from the visual and sensomotor cortex, the lateral geniculate nucleus, the hypothalamus and the caudate nucleus in normal cats and after bilateral lesion of the specific visual pathways. The light-imduced EPs were preserved after transection of the optical tracts and after lesion of the lateral geniculate nuclei. The EPs to flashes were absent after transection of the optical nerves. After lesion of the lateral geniculate nuclei, sparing all optical tract connections to the colliculi superior, activation of the EEG was possible with strong light flashes. The significance of the retino-hypothalamic and retino-collicular connection for formation of the light-induced cortical responses, is discussed.