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Output architecture of the primate putamen
1Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge 02139.
Summary
Neurons in the basal ganglia form clusters projecting to either the external or internal pallidum, not both. This clustering within the striatal matrix may coordinate signals in the direct and indirect pathways.
Area of Science:
- Neuroscience
- Basal Ganglia Research
- Motor Control
Background:
- The basal ganglia's direct and indirect pathways influence cortical activity, potentially explaining hyperkinetic and hypokinetic movement disorders.
- Previous research suggested a link between these pathways and striatal compartments, but evidence was inconclusive.
Purpose of the Study:
- To investigate if striatopallidal output pathways are organized into distinct clusters within the striatal matrix.
- To determine if specific clusters project to the external pallidum (GPe) or internal pallidum (GPi).
Main Methods:
- Retrograde labeling of striatal output neurons in squirrel monkeys after injections into GPe and GPi.
- Comparing the distribution of neurons labeled from GPe and GPi.
- Analyzing double-retrograde labeling and enkephalin immunoreactivity in labeled neurons.
Main Results:
- Striatopallidal neurons formed distinct clusters ('matrisomes') within the putamen's matrix.
- Clusters projecting to GPe and GPi overlapped extensively and contained intermixed neurons.
- Most neurons projected to either GPe or GPi, with very few projecting to both.
- GPe-projecting neurons were predominantly enkephalin-positive, while GPi-projecting neurons were mostly enkephalin-negative.
Conclusions:
- Striatopallidal output neurons in primates are organized into matrix clusters (matrisomes).
- Individual neurons within a cluster project to either GPe or GPi, not both.
- Matrisomal organization may coordinate signaling within the basal ganglia's direct and indirect pathways.