Quantitative data on cell loss and cellular atrophy of intralaminar nuclei following cortical and subcortical lesions.

Morphological changes in the intralaminar nuclei centralis medialis, paracentralis and centralis lateralis of the thalamus of adult cats after cortical excisions have been determined by means of a quantitative method. The number and size of the remaining neurons on the operated side have been compared with those of the normal side. The differences between the normal and the operated side have been compared to those found between the two sides in the control animals. The most important result is the demonstration that after cortical ablations the intralaminar nuclei show not only chromatolytic or atrophic changes of their cells but also a true cell loss. These reactions are qualitatively similar to those observed in the specific nuclei of the thalamus, the only difference being a quantitative one. As a consequence it can be suggested that some intralaminar nuclei project to certain areas of the cerebral cortex which also receive projections from one or other specific thalamic nucleus. A large essential connection of the intralaminar nuclei, in particular the nucleus centralis medialis, with subcortical structures is confirmed.