[Long term transformation of neuronal activity in the superior colliculus isolated from corticofugal influences]

Neuronal activity of the superior colliculus isolated from the corticofugal influences was studied in various periods of time (from 3 to 20 months) after unilateral dissection of cortico-subcortical projections. In 16 unanesthetized immobilized cats, after the surgery, spontaneous activity of collicular neurons became more regular and with less complex bursts during the postoperative period. Evoked activity was completely suppressed during early hours of the postoperative period. Only 31.5% of collicular cells were sensitive to light 3 months after the operation. Evoked responses to light of 90.4% cells reappeared in the isolated colliculus not earlier than 10-12 months after the isolation, while directional and movement sensitivity practically did not restore even within 20 months after the surgery. Corticocollicular influences are considered to be a necessary condition for effective visual information processing in the colliculi superiores.