The functional organization of the descending influences in the non-projection corticothalamic systems of the cat brain.

The local cooling of parietal, frontal or motor cortical areas; in cats under Nembutal anesthesia changed evoked potentials (EPs) in pulvinar, lateral posterior and medial dorsal thalamic nuclei. Parietal cortex, cooling led to rapid and significant changes of visual EP and delayed but strong changes of somatic EP in the pulvinar-lateral posterior complex. In contrast, frontal cortex cooling led to fast changes of somatic EP in medial dorsal nucleus and caused delayed weak changes: of visual EP. Motor cortex cooling resulted in rapid transformations of both potentials, though the changes of somatic EP were more pronounced in medial dorsal nucleus. The modifications of both EP primary-and secondary components were modal- and system-dependent. Results suggest that polysensory cortical areas exert modal-specific corticofugal influences on signals of different modality or on signals of the same modality but different subcortical genesis in the association nuclei.