THALAMOCORTICAL PATHWAYS UNDERLYING THE SPATIAL REPRESENTATION OF TEMPERATURE AND TOUCH IN MOUSE POSTERIOR INSULAR CORTEX

Spatial representations of sensory modalities in the cortex typically reflect structured input from thalamic pathways. In the mouse forepaw primary somatosensory cortex (fS1), thermal and tactile representations overlap, whereas they are spatially segregated in the posterior insular cortex (pIC) (Milenkovic et al., 2014; Vestergaard et al., 2023). We hypothesize that this segregation in pIC arises from modality-specific thalamic input streams conveying thermal or tactile information. To test this hypothesis, we combined cortical imaging, anatomical tracing, and ex-vivo electrophysiology. Widefield cortical calcium imaging in awake, head-fixed mice confirmed overlapping thermo-tactile representations in fS1 and spatially separated representations in pIC. Imaging of thalamic axons within the pIC revealed a similar thermo-tactile segregation, suggesting that the cortical organization is driven by thalamic input. To identify the thalamic source of these inputs, we combined anterograde and retrograde tracing of candidate thalamic nuclei. Finally, whole-cell patch clamp recordings combined with optogenetic activation of thalamocortical axons in acute brain slices are being used to assess the functional connectivity and synaptic properties of these pathways. Together, these results support a thalamic origin for the spatial segregration of thermal and tactile cortical sensory representations.