The pars reticulata of the substantia nigra: a window to basal ganglia output

The subthalamo-pallidal system constitutes the second layer of circuitry in the basal ganglia, downstream of the striatum. It consists of four nuclei. Two of them, the external segment of the globus pallidus (GPe) and subthalamic nucleus (STN), make their connections primarily within the basal ganglia. The others, the internal segment of the globus pallidus (GPi) and the substantia nigra pars reticulata (SNr), are the output nuclei of the basal ganglia. Collectively, their axons distribute collaterals to all the targets of the basal ganglia. Rare interneurons have been reported in each of them from studies of Golgi-stained preparations, but they have not so far been confirmed using more modern methods. The circuit as described here is based primarily on studies of the axonal arborizations of neurons stained individually by intracellular or juxtacellular labeling.

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Basal Ganglia Control of Substantia Nigra Dopaminergic Neurons

Birth, Life and Death of Dopaminergic Neurons in the Substantia Nigra ◽

10.1007/978-3-211-92660-4_6 ◽

2009 ◽

pp. 71-90 ◽

Cited By ~ 5

Author(s):

Christian R Lee ◽

James M Tepper

Keyword(s):

Basal Ganglia ◽

Substantia Nigra ◽

Dopaminergic Neurons

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Lack of Spike-Count and Spike-Time Correlations in the Substantia Nigra Reticulata Despite Overlap of Neural Responses

Journal of Neurophysiology ◽

10.1152/jn.00190.2007 ◽

2007 ◽

Vol 98 (4) ◽

pp. 2232-2243 ◽

Cited By ~ 20

Author(s):

Alon Nevet ◽

Genela Morris ◽

Guy Saban ◽

David Arkadir ◽

Hagai Bergman

Keyword(s):

Basal Ganglia ◽

Substantia Nigra ◽

Information Transfer ◽

Spike Timing ◽

Spike Count ◽

Unique Event ◽

Correlated Activity ◽

Different Types ◽

Substantia Nigra Reticulata ◽

Response Task

Previous studies of single neurons in the substantia nigra reticulata (SNr) have shown that many of them respond to similar events. These results, as well as anatomical studies, suggest that SNr neurons share inputs and thus may have correlated activity. Different types of correlation can exist between pairs of neurons. These are traditionally classified as either spike-count (“signal” and “noise”) or spike-timing (spike-to-spike and joint peristimulus time histograms) correlations. These measures of neuronal correlation are partially independent and have different implications. Our purpose was to probe the computational characteristics of the basal ganglia output nuclei through an analysis of these different types of correlation in the SNr. We carried out simultaneous multiple-electrode single-unit recordings in the SNr of two monkeys performing a probabilistic delayed visuomotor response task. A total of 113 neurons (yielding 355 simultaneously recorded pairs) were studied. Most SNr neurons responded to one or more task-related events, with instruction cue (69%) and reward (63%) predominating. Response-match analysis, comparing peristimulus time histograms, revealed a significant overlap between response vectors. However, no measure of average correlation differed significantly from zero. The lack of significant SNr spike-count population correlations appears to be an exceptional phenomenon in the brain, perhaps indicating unique event-related processing by basal ganglia output neurons to achieve better information transfer. The lack of spike-timing correlations suggests that the basal high-frequency discharge of SNr neurons is not driven by the common inputs and is probably intrinsic.

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