Use of animal models in study of recovery functions after brain lesions.

We studied the effects of selective exclusions of the classical and commissural pathways in the visual and somatosensory systems in cats on 1) Conditioning (instrumental conditioned reflexes), 2) Electrophysiological responses in specific, related and distinct brain structures and 3) Gross neurological and behavioral changes. Transections within main projection inputs to thalamic relay nuclei (lateral geniculate body for the visual and VPL-VPM complex for the somatosensory system) on one side of the brain, as well as of the commissures of the telencephalon, diencephalon and mesencephalon, reduce but do not abolish visual and somatosensory evoked responses on both hemispheres. Follow-up studies of the gross neurological (dysmetria, ataxia, myogenic atony, anisocoria) and behavioral (motor habituation) changes, after these transections, showed that the deficits were unstable and disappeared mostly within two months, except the anisocoria which lasted longer.