Effects of subcortical electrolytic lesions on the head-eye turning response induced by electrical stimulation of the cat's pulvinar-lateralis posterior nucleus complex.

The relations between three subcortical structures and P-LP, all of them capable of inducing contralateral head-eye turning responses when electrically stimulated, were studied in three groups of cats. In all the experiments stainless steel electrodes were chronically implanted in P-LP and in each group of five cats. Electrodes were also placed respectively in the caudate nucleus, superior colliculus and nucleus centralis lateralis. Series of current intensity threshold values for evoking head-eye turning responses were determined in each group, before and after electrolytic lesion of these three subcortical structures. The total observation period was approximately 30 days. Only the destruction of the superior colliculus produced the loss of the ability of the ipsilateral P-LP to evoke turning response. According to these results it is postulated that the efferent pathway that carries the information for turning response from P-LP runs through the ipsilateral superior colliculus.