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The efferent projections of the subthalamic nucleus were studied with the autoradiographic tracing technique in Rhesus monkey and cat. From the data it appears that the major efferent projections of the nucleus are to the pallidal complex and the substantia nigra. In both monkey and cat, the projection to the pallidal complex is truly massive and is directed at both pallidal segments. The projection field includes an infracommissural part of the pallidal complex bordering on the substantia innominata. In the monkey the termination in the pallidal complex is organized in several characteristic bands oriented parallel to the medullary laminae. The subthalamo-pallidal projection in monkey further appears to be topographically organized. The projections to the substantia nigra is prominent in both cat and monkey though not as massive as that to the pallidal complex. The distribution of termination in the substantia nigra favors the more ventral strata near the cerebral peduncle. In the monkey the terminal distribution appears to avoid regions of the substantia nigra containing pigmented neurons and it is suggested that the subthalamo-nigral pathway may prefer non-dopaminergic neurons. In addition to the above major projections, sparse projections were noted to the thalamic nuclei ventralis lateralis and ventralis anterior, to the putamen, and to the mesencephalic nucleus tegmenti pedunculopontinus, pars compacta. The findings are discussed.

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Hereditary dysphasic dementia is described in terms of its clinicopathological, ultrastructural, and transmissibility characteristics. Its mode of inheritance is autosomal dominant, and its clinical manifestations of progressive dementia and severe dysphasic disturbances are expressed in late adulthood. Complete neuropathological examination of four patients reveals findings typical for Pick's disease (asymmetrical focal cerebral atrophy), Alzheimer's disease (profuse neuritic plaques), and paralysis agitans (neuronal depigmentation, depletion, and Lewy body formation in substantia nigra) in addition to a striking but nonspecific spongiform degeneration of superficial cortical layers. This unique combination of gross morphological and histopathological features qualifies hereditary dysphasic dementia as a distinct entity, but its precise relationship to the well-recognized adult cortical dementias has been difficult to establish by conventional classification methods. This disorder and other unusual dementing illnesses may be best considered as part of a Pick-Alzheimer spectrum of cortical neuronal degenerations.