Two Different Types of Thalamocortical Projections to a Single Cortical Area in Mammals; pp. 141–155

Abstract

There are two distinct types of thalamocortical projections to parietal cortex in the opossum and the hedgehog. Both projections arise from the posterior portion of the ventral nuclear group of the dorsal thalamus which may be subdivided into two nuclei. First, the ventral posterior nucleus which receives a homogenous somatic sensory input and projects in a restricted fashion to layer IV of parietal cortex. Second, the central intralaminar nucleus which receives a heterogenous input from somatic sensory nuclei, the cerebellum and the midbrain reticular formation and projects diffusely to layers I and VI of parietal cortex and to the basal telencephalic nuclei. The two projections are discussed in terms of specific and unspecific thalamocortical systems and as a basis for the concepts of essential and sustaining thalamocortical projections.