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Output systems of the dorsal column nuclei in the cat

1986; Elsevier BV; Volume: 11; Issue: 3 Linguagem: Inglês

10.1016/0165-0173(86)90012-3

1872-6321

Karen J. Berkley, Richard J. Budell, Anders Blomqvist, Mark S. Bull,

Axon Guidance and Neuronal Signaling

Numerous authors have demonstrated that the dorsal column nuclear complex (DCN) is functionally heterogeneous and has multiple terminal targets throughout the neuroaxis. In order to increase understanding of the functional significance of DCN's divergent connections, the present study used single and double light microscopic retrograde tracing strategies in the cat to characterize the location and morphology of DCN neurons that project to different portions of the diencephalon, rostral mesencephalon and spinal cord. These neuronal populations were then compared with those (previously reported from this and other laboratories) that project to the caudal mesencephalon, pons, inferior olive and cerebellum. When the results are considered together, a tentative picture of DCN emerges in which a population of clustered neurons that project exclusively to VPL form a core that is surrounded by and infiltrated with neurons projecting to other parts of the nervous system. Although the neuronal populations projecting to each of the different targets were individually separable anatomically by their location and/or morphological characteristics, previously reported physiological and other anatomical evidence permitted a preliminary grouping of these populations into 3 main systems (see Fig. 8). The first, a sensory tactile and kinesthetic 'cortical' system, consisted of 3 components: (a) a double core of round, clustered medium-sized neurons (one each in the gracile and cuneate nuclei) and a variform rostral group projecting to the ventroposterolateral nucleus (VPL), (b) a ventral group of unclustered large round neurons in the middle cuneate nucleus and a dense group of neurons in nucleus Z projecting to VPL's border with the ventrolateral nucleus (VPL/VL), and (c) a group of mainly small-sized neurons located between the clusters of neurons or in the thin dorsal rim around the caudal and middle portions of the double cores and a populous, variform rostral group projecting indirectly (and possibly directly) to the posterior group through the intercollicular region of the tectum69. The second, a sensorimotor 'cerebellar' system, consisted of multiple, subtly separable populations of neurons with different morphological characteristics all of which were located in different parts of the complex region that surrounds the cores on all sides. These neurons projected to restricted portions of interconnected targets31 within the zona incerta, tectum11, pretectum, red nucleus, pontine grey82, pontine raphe79, inferior olive90,91 and cerebellum34. The third, a feedback 'spinal' system, consisted of morphologically diverse, but predominantly large neurons located mainly ventrally between the cuneate and gracile nuclei projecting to the spinal cord. Thus, the cuneate and gracile nuclei not only appear to serve a role in tactile sensation and kinesthesia by topographically relaying precise cutaneous and proprioceptive information through VPL and VPL/VL to the cerebral cortex, but they also appear to serve complex, feedback-regulated roles in sensorimotor integration by systematically channeling and transmitting a variety of other types of somatic information to other parts of the nervous system.