Organization of the posterior dorsal thalamus of the hedgehog.

Abstract

AbstractA study of the responsiveness of single neurons in the hedgehog thalamus to sensory stimulation was undertaken with the hypothesis that modality specific relay nuclei characteristic of the mammalian thalamus differentiate out of a pool of multisensory neurons. Support for this hypothesis was obtained in earlier investigations of the opossum thalamus. In some ways the hedgehog may be an even better representative of a primitive stage of thalamic development. For example, there is very little structural difference between the ventroposterior nucleus and the medial geniculate body. The results of the present microelectrode investigation showed that neither the ventroposterior nucleus nor the medial geniculate body was modality specific. Further, many neurons in the ventroposterior nucleus showed wide receptive fields characteristic of the posterior group of nuclei in cats. This finding of convergence of sensory input upon single neurons of the dorsal thalamus in a generalized mammalian type suggests that the specificity characteristic of higher mammals is a product of an evolutionary trend. Thus comparative neurology provides additional evidence that precise receptive fields must play an important role in behavioral adaptation.