NEURONAL CIRCUITRY AND CELLULAR ORGANIZATION OF THE MOUSE CLAUSTRUM IN RELATION TO THE MPFC, AMYGDALA, AND CORTICAL LAYER 6B

Anatomical studies have suggested that the claustrum is reciprocally connected with a wide range of neocortical regions involved in multiple sensory modalities. The medial prefrontal cortex (mPFC) is recognized as a key center for top-down control of sensory processing, and the claustrum has been proposed to function as a network hub mediating top-down modulation of sensory attention. However, direct synaptic connectivity among the mPFC, claustrum, and sensory cortices has not yet been firmly established. In addition to cortical inputs, subcortical structures such as the basolateral amygdala (BLA) have been implicated in claustral circuitry, but it remains unclear whether individual claustral neurons send axonal collaterals to multiple target regions, including the BLA. Furthermore, despite their close anatomical proximity, the relationship between the claustrum and cortical layer 6b has not been systematically investigated. In the present study, we characterize the connectivity between the mPFC and the claustrum, as well as between the amygdala and the claustrum. We further compare the cellular architecture of layer 6b neurons and the claustrum to delineate their similarities and distinctions. Together, our findings reveal the extensive brain-wide connectivity of the claustrum and highlight its unique properties as a central hub positioned at the base of the cortex.