Convergence of forepaw somatosensory and motor cortical projections in the striatum, claustrum, thalamus, and pontine nuclei of cats

Abstract

The basal ganglia and pontocerebellar systems regulate somesthetic-guided motor behaviors, and receive prominent inputs from sensorimotor cortex. Additionally, the claustrum and thalamus are forebrain subcortical structures that have connections with somatosensory and motor cortices. Our previous studies in rats have shown that primary and secondary somatosensory cortex (S1 and S2) send overlapping projections to the neostriatum and pontine nuclei, whereas overlap of primary motor cortex (M1) and S1 was much weaker. Additionally, we have shown that M1, but not S1, projects to the claustrum in rats. The goal of the current study was to compare these rodent projection patterns with connections in cats, a mammalian species that evolved in a separate phylogenetic superorder. Three different anterograde tracers were injected into the physiologically identi ed forepaw representations of M1, S1, and S2 in cats. Labeled bers terminated throughout the ipsilateral striatum (caudate and putamen), claustrum, thalamus, and pontine nuclei. Digital reconstructions of tracer labeling allowed us to quantify both the normalized distribution of labeling in each subcortical area from each tracer injection, as well as the amount of tracer overlap. Surprisingly, in contrast to our previous ndings in rodents, we observed M1 and S1 projections converging prominently in striatum and pons, whereas S1 and S2 overlap was much weaker. Furthermore, whereas rat S1 does not project to claustrum, we con rmed dense claustral inputs from S1 in cats. These ndings suggest that the basal ganglia, claustrum, and pontocerebellar systems in rat and cat have evolved distinct patterns of sensorimotor cortical convergence.

Role of Posterior Medial Thalamus in the Modulation of Striatal Circuitry and Choice Behavior

“…73,74,77 For example, M1 and S1 are heavily interconnected via reciprocal L2/3 and L5 connections, 78,79,80 and their projections overlap within dorsal striatum and even onto the same neuron. 73,81,82,83,84,85,86 While some studies treat striatal inputs as a uniform entity, 87,88 they have been shown to differ anatomically, 73,74,76 functionally, 89,90 and behaviorally. 89,91,92 Thus, the specific cortical and thalamic origin of striatal inputs likely has significance for understanding how the striatal circuitry integrates sensorimotor information to modulate behavior.…”

Cell-Type Specific Connectivity of Whisker-Related Sensory and Motor Cortical Input to Dorsal Striatum

“…Notably, the dorsolateral striatum (DLS) is a site of overlap between inputs from M1 and S1 and plays a critical role in sensorimotor integration (Hoffer & Alloway, 2001;Hunnicutt et al, 2016;Makino et al, 2016;Hooks et al, 2018;Smith et al, 2022), but how these inputs are integrated by different cell types in DLS is still unclear.…”

“…Generally, cortical projections from functionally related brain regions show higher density and significant overlap amongst their projection fields in the striatum (Bolam et al, 2002; Hintiryan et al, 2016; Hunnicutt et al, 2016). Notably, the dorsolateral striatum (DLS) is a site of overlap between inputs from M1 and S1 and plays a critical role in sensorimotor integration (Hoffer & Alloway, 2001; Hunnicutt et al, 2016; Makino et al, 2016; Hooks et al, 2018; Smith et al, 2022), but how these inputs are integrated by different cell types in DLS is still unclear.…”

Cell-Type Specific Connectivity of Whisker-Related Sensory and Motor Cortical Input to Dorsal Striatum

“…Generally, cortical projections from functionally related brain regions show higher density and significant overlap amongst their projection fields in the striatum ( Bolam et al, 2002 ; Hintiryan et al, 2016 ; Hunnicutt et al, 2016 ). Notably, the dorsolateral striatum (DLS) is a site of overlap between inputs from M1 and S1 and plays a critical role in sensorimotor integration ( Hoffer and Alloway, 2001 ; Hunnicutt et al, 2016 ; Makino et al, 2016 ; Hooks et al, 2018 ; Smith et al, 2022 ), but how these inputs are integrated by different cell types in DLS is still unclear.…”