3. Less is more and more is less: hyper- and hypoconnectivity demystified

COEX 

This talk will demystify some misconceptions related to the use of fMRI connectivity to infer underlying patterns of brain activity and connectivity. Specifically, empirical evidence of topographic convergence between structural and functional connectivity has prompted the widely held assumption that structural connectivity (i.e., axonal output) drives fMRI connectivity. Within this framework, reduced or increased activity in a brain region should thus result in reduced (hypo-) or increased (hyper-) connectivity with the region’s targets. This talk will challenge this conceptual framework by presenting the results of chemogenetic and electrophysiological studies in mice showing how fMRI hyper- and hypoconnectivity may counterintuitively reflect reduced and increased cortical activity, respectively. This updated framework may offer novel opportunities to biologically decode fMRI dysconnectivity in human disorders.