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Topographic organization of medial pulvinar connections with the prefrontal cortex in the rhesus monkey
L M Romanski1, M Giguere, J F Bates
1Section of Neurobiology, Yale University School of Medicine, New Haven, Connecticut 06510, USA. romanski@biomed.med.yale.edu
Abstract:
The medial nucleus of the pulvinar complex (PM) has widespread connections with association cortex. We investigated the connections of the PM with the prefrontal cortex (PFC) in macaque monkeys, with tracers placed into the PM and the PFC, respectively. Injections of wheat germ agglutinin-horseradish peroxidase (WGA-HRP) placed into the PM resulted in widespread anterograde terminal labeling in layers III and IV, and retrograde cellular labeling in layer VI of the PFC. Injections of tracers centered on the central/lateral PM resulted in labeling of dorsolateral and orbital regions, whereas injections centered on caudal, medial PM resulted in labeling of dorsomedial and medial PFC. Since injections of the PM included neighboring thalamic nuclei, retrograde tracers were placed into distinct cytoarchitectonic regions of the PFC and retrogradely labeled cells in the posterior thalamus were charted. The results of this series of tracer injections confirmed the results of thalamic injections. Injections placed into areas 8a, 12 (lateral and orbital), 45, 46 and 11, retrogradely labeled neurons in the central/lateral PM, while tracer injections placed into areas 9, 12 (lateral), 10 and 24, labeled medial PM. The connections of the PM with temporal, parietal, insular, and cingulate cortices were also examined. The central/lateral PM has reciprocal connections with posterior parietal areas 7a, 7ip, and 7b, insular cortex, caudal superior temporal sulcus (STS), caudal superior temporal gyrus (STG), and posterior cingulate, whereas medial PM is connected mainly with the anterior STS and STG, as well as the cingulate cortex and the amygdala. These connectional studies suggest that the central/ lateral and medial PM have divergent connections which may be the substrate for distinct functional circuits.
Insights
The medial pulvinar nucleus (PM) in macaque monkeys connects with the prefrontal cortex (PFC). Distinct subregions of the PM show specific connections with different PFC areas, suggesting specialized functional circuits.
Area of Science:
- Neuroscience
- Primate Brain Anatomy
- Thalamocortical Connections
Background:
- The medial nucleus of the pulvinar complex (PM) is known for its extensive connections with the association cortex.
- Understanding the precise connectivity of the PM with the prefrontal cortex (PFC) is crucial for elucidating higher cognitive functions.
Purpose of the Study:
- To investigate the detailed anatomical connections between the medial nucleus of the pulvinar complex (PM) and the prefrontal cortex (PFC) in macaque monkeys.
- To determine if different subregions of the PM have distinct connection patterns with specific PFC areas.
Main Methods:
- Utilized wheat germ agglutinin-horseradish peroxidase (WGA-HRP) and retrograde tracers injected into the PM and PFC of macaque monkeys.
- Mapped anterograde and retrograde labeling patterns to identify specific connection sites within the PFC and posterior thalamus.
- Examined connections with temporal, parietal, insular, and cingulate cortices.
Main Results:
- PM injections resulted in widespread labeling in PFC layers III, IV, and VI.
- Central/lateral PM connected with dorsolateral and orbital PFC regions (areas 8a, 12, 45, 46, 11).
- Medial PM connected with dorsomedial and medial PFC regions (areas 9, 12, 10, 24), as well as cingulate cortex and amygdala.
Conclusions:
- The medial pulvinar nucleus exhibits segregated connections with distinct regions of the prefrontal cortex.
- Central/lateral and medial PM subregions possess divergent connectional pathways, likely forming the basis for separate functional circuits.
- These findings contribute to understanding the neural substrates underlying complex cognitive processes involving the PFC and pulvinar complex.