Strio-pallidal projection in the monkey.

Abstract

The corpus striatum in the mammalian brain appears to receive only two major groups of afferents: from the intralaminar nuclei of the thalamus and from most areas of the cerebral cortex. A common feature of both groups of afferents is their well-developed topographical organization. Rostral and caudal parts of the thalamus and cortex are related to the corresponding parts of the striatum (Powell and Cowan, 1956;Webster, 1961 Webster, , 1965Carman, Cowan, and Powell, 1963); in the medio-lateral dimension the organization is more complex, and does not conform, as might have been supposed, to the simple division of the striatum into a medial caudate nucleus and a laterally placed putamen. Instead, the available evidence suggests that the efferents from the greater part of the cerebral cortex and most of the intralaminar nuclei terminate on both sides of the internal capsule. Thus, for example, in the rabbit the cortex on the dorso-lateral surface of the hemisphere sends fibres both to the caudate and putamen (Carman et a!., 1963), and in the monkey, following a lesion in the centromedian nucleus degenerating fibres can be traced into both the caudate and putamen (Mehler, 1966).In view of this evidence it was of some interest to determine whether the functional organization imposed upon the architectonically homogeneous striatum by its afferents is reflected also in its efferent connexions. Our attention was drawn to this question several years ago when studying the thalamo-striate connexions (Powell and Cowan, 1956) because in most of the material used in that study discrete areas of intense gliosis were observed in different parts of the globus pallidus and substantia nigra with experiments involving varying portions of the caudate nucleus and putamen. The publication in 1960 and 1962 of papers by Voneida and by Szabo on the distribution of striatal efferents showed a close correspondence between the pattern of the projection of the striatum as determined by the Nauta method and our own findings on the distribution of gliosis in our earlier material and in several additional brains prepared since that time (Powell and Cowan, 1966). It was considered worthwhile, therefore, to put our observations on record not only because they provide independent confirmation of the organization of strio-pallidal and strio-nigral connexions, but also because they demonstrate the value of the study of the distribution of gliosis as an analytical method in fibre systems in which the direction of conduction is known.The organized nature of the afferent and efferent connexions of the striatum has assumed greater significance with the demonstration by Nauta and Mehler (1966) that the small-celled external segment of the globus pallidus sends fibres only to the subthalamic nucleus, whereas the large-celled inner segment is related to the thalamus and midbrain.Their additional finding that part of the projection from the internal segment is to the centromedian nucleus is of particular interest: first, because it may provide a 'circula...

The monkey globus pallidus: neuronal discharge properties in relation to movement.

“…The termination of the cortico-striatal projection to this region was arranged in multiple patches, each patch separated from the other by 05-2 0 mm. Further, the strio-pallidal projection has been shown to be organized in such a way that the upper half of the putamen projects to the upper part of both segments of the globus pallidus (Szabo, 1962(Szabo, , 1967(Szabo, , 1968Cowan & Powell, 1966;Kim, Nakano, Jayaraman & Carpenter, 1976). These anatomical data are consistent with the findings in this report of the presence of arm movement related units in the upper half of the external globus pallidus and of the clustered arrangement of such units.…”

Observations on the fine structure of the substantia nigra in the cat

“…This subdivision, furthermore, seems to gain substantial support from experimental studies on its afferent fibre connections in animals (Voneida, 1960;Szabo, 1962Szabo, , 1967Szabo, , 1969Nauta and Mehler, 1966 ;Cowan and Powell, 1966). We agree that a distinction between pars compacta and pars reticulata is a useful one from a pure descriptive point of view.…”

Morphometric studies of the neuropathological changes in choreatic diseases

“…The supposition of transneuronal degeneration in the pallidum as a result of a lesion in the striatum is not confirmed either by experimental findings . After localized lesions in the striatum Cowan and Powell (1966) could not detect any atrophy or loss of nerve cells in the pallidum but only local gliosis . The pallidal nerve cell density increased .…”