New functional insights from the monkey claustrum.

The claustrum is a subcortical nucleus with widespread, reciprocal connections to the cortex and beyond, inspiring many models of its function. Decades of work from rodents provide a foundational understanding of the anatomy and functional organization of the claustrum, which is more recently aided by human functional neuroimaging studies. However, important questions remain with broad functional implications. These center on claustrum anatomical boundaries, functional organization, and the putative expansion of human claustrum connectivity over that predicted by rodent studies alone. Providing new insights by spanning the large rodent-to-human void, a landmark study by Lei and colleagues recently provided thorough molecular and connectivity profiling of the macaque claustrum. Surprising findings of lateralized and expanded claustrum connectivity with cortical and subcortical partners help to explain human functional connectivity data and the discovery of a well-developed organization of the monkey claustrum into overlapping functional sub-domains provides deep insight into claustrum function when considering rodent synaptic connectivity data. Contextualizing these findings, we provide an elaborated model of the function of the claustrum in cognition.