[Role of the pulvinar lateralis posterior complex on the rotation response. Relation with other cerebral structures. Pharmacological systems involved in this behavior].

A critical analysis of the results obtained in four experimental series of cats is presented. In these experiments the following results are shown: 1) Electrical stimulation of the pulvinar-lateral posterior nucleus complex (P-LP) evokes a contralateral turning of the head accompanied by similar directional rotation of both eyes, most of them of the saccadic type. With higher intensity currents contralateral circling is produced. 2) The motor output of the P-LP is through the ipsilateral superior colliculus. Electrolytic lesion of this last structure suppresses the turning behavior induced by electrical stimulation of the P-LP. The same result is not obtained when the ipsilateral caudate nucleus, or the nucleus centralis lateralis of the thalamus are lesioned. 3) The ablation of the ipsilateral cerebral cortex having important reciprocal connections with P-LP, produces in 50% of the cats studied, in the first week after the ablation, a suppression of the turning response. However at 30 days after the surgical procedure, 86% of the electrodes implanted in P-LP are able to induce a turning response by electrical stimulation. 4) The local injection into P-LP, through a cannula, of carbachol or dioxolane (an exclusive muscarinic receptor activator) produces also contralateral head-eye-body turning response. We postulate the P-LP as another structure related to turning, different from the nigro-striatal system. This last one is not affected by lesioning of the superior colliculus, as happens with the P-LP. On the other hand, the main putative neurotransmitter involved in the nigro-striatal system is dopamine, whereas in P-LP is probably acetylcholine.