Sensory‐motor processing in substantia nigra pars reticulata in conscious cats.

Abstract

SUMMARY1. Extracellular recordings were made with chronically implanted micro-electrodes from 109 substantia nigra neurones in conscious cats. Ninety-six of 109 neurones met the criteria of presumed non-dopaminergic pars reticulate (s.n.r.) neurones. Background discharge, in animals in a state of relaxed wakefulness and in the absence of overt movements, was in the range of 11-37 impulses/s, mean 19-2 impulses/s.2. The discharges of fifty-two of ninety-six neurones tested were modified by innocuous mechanical skin stimulation. Neurones responded chiefly to stimuli delivered to the contralateral body side. Responses generally comprised net excitation and occurred with short latency (range 10-34 ms; mean 17-3 ms). Convergence from both forelimbs or the contralateral fore-and hind limbs was evident in a few cases. 3. One-fourth (twenty-four out of ninety-six) of the s.n.r. neurones tested were sensitive to passive manipulation of limb joints in the quiet, conscious cat and responded exclusively to angular displacement of one contralateral joint. Responses were directional and phasic.4. None of the s.n.r. neurones tested responded to clicks and/or light flashes. However, stimuli moving across the contralateral visual field substantially modified the discharge rate of ten out of ninety-six s.n.r. neurones. Responses were directional and invariably associated with eye movements.5. Animals were also trained to walk on a treadmill and to perform certain self-generated limb movements. S.n.r. neurones with a receptive field on a limb regularly showed modulations in discharge during locomotion, phase-related to the step cycle, and also short-latency responses during disturbance of such movements.6. Ten out of ninety-six s.n.r. neurones discharged almost exclusively prior to and during self-generated movements of a single limb. Their most powerful modulations in firing rate occurred, whenever an animal tried to overcome an external impediment or to resist an imposed movement.7. These observations on s.n.r. neurones, taken together with previous findings on nigral influences on spinal motor circuitry, indicate that the s.n.r. represents an output station of the basal ganglia which is involved in the subconscious processing of convergent multimodal sensory information and which participates in setting appropriate gains and biasses of spinal motor neuronal systems to adequately deal with changing motor requirements. 5PHY 347

Activity in monkey substantia nigra neurons related to a simple learned movement

“…A considerable percentage of SN cells was related to movements of the upper limb confirming results obtained in the SNc of rats (Diana et al 1989) and in the SNr of cats (Schwarz et al 1984) and monkeys (Nishino et al 1985), but in contrast to other reports , Schultz 1983). The differences may be due to the distinct experimental approach followed.…”

The deep mesencephalic nucleus as an output center of basal ganglia: Morphological and electrophysiological similarities with the substantia nigra

“…Some data suggest that the DMN could also be involved in basal ganglia functions. Particularly interesting in this respect is the parallelism observed between the DMN and SN pars reticulata (SNR), a nucleus that plays an important role in motor response and in the pathophysiology of basal ganglia diseases (DeLong et al, 1983;Schwarz et al, 1984;Schultz, 1986;Schultz and Romo, 1990;Obeso et a., 1997). Both the SNR (Gonzá lez-Herná ndez and and DMN (Mugnaini and Oertel, 1985;Appell and Behan, 1990;Esclapez et al, 1993) are composed of GABAergic neurons.…”

Processing of dynamic visual information in the caudate nucleus

“…Earlier studies suggested that the CN is involved in visuomotor behavior and contributes to the control of visually guided oculomotor and skeletomotor functions (Lynd-Balta & Haber, 1994;Hikosaka, et al, 2000;Schwarz, et al, 1984;Barneoud, et al, 2000). Based on our results we can conclude that the dynamic component of the visual information is represented in two different ways in the CN.…”