Preferential medial claustrum input and orbitofrontal output of the rostral-to-striatum claustrum in rats

The claustrum is a thin, elongated structure that forms widespread reciprocal connections with most cortical areas and has been proposed to support diverse functions. Recent studies in rats have suggested that the anterior claustrum, particularly the rostral-to-striatum claustrum (rsCla), may serve as a hub for information integration. However, the connectivity between the rsCla and other brain regions remains poorly understood. In the present study, we examined the connectivity of the rsCla in rats using retrograde tracers. Consistent with previous studies of other claustral regions in rodents, the rsCla exhibited widespread reciprocal connectivity with multiple cortical areas. In contrast, it received relatively strong input from the medial claustrum and showed preferential output to the orbitofrontal cortex. These findings suggest that the rsCla may integrate inputs from the medial claustrum, potentially reflecting more processed signals, together with distributed cortical information, and transmit this integrated representation preferentially to the orbitofrontal cortex, supporting outcome prediction.