Third, the hypotheses we chose to test provide only an initial demonstration of the sensitivity of resting state fMRI functional connectivity to layer-specific functional microcircuits in the human brain. However, further fine-grained investigations are possible. This could involve specific thalamo-cortical pathways from other thalamic nuclei, specifically in systems that are unique in humans and for which we do not have reliable homologues in animals, and hence are not amenable to invasive investigations. For example, two parallel layer-specific pathways connect language-related thalamic nuclei to layer I and middle layers of Broca’s area. The cortico-thalamic radiations from Broca’s area in turn originate from cortical layers V and VI. Dysfunction in these pathways are important in aphasic patients with damage to the thalamic nuclei [76]. Our study opens the possibility of characterizing such layer-specific microcircuits, both in healthy and clinical populations, using ultra high field fMRI in the future.
