Professor Massachusetts Institute of Technology, United States
Introduction: The brain consists of a complex network of interconnected regions that work together to process information and generate behavior. Studying how these regions communicate reveals how information flows and transforms during perception, cognition, and behavior. Functional imaging techniques such as functional MRI provide valuable insight into these functions at whole brain sclae, but lacks the specificity to pinpoint specific network activities for circuit level analysis.
Materials and
Methods: We studied interregional communication in the brain by applying a genetically encoded probe called NOSTIC in anesthetized rats and awake marmosets. NOSTIC transduces intracellular calcium activity into hemodynamic responses from neural circuit elements that express the probe; the hemodynamic responses can be detected at a brain-wide scale by functional neuroimaging techniques. We used a retrogradely transported viral vector to selectively target NOSTIC expression to neurons that project to viral injection sites. We then performed functional MRI in the presence and absence of a NOSTIC-specific inhibitor to measure information flow over the labeled projections in the rodent somatosensory system and the primate visual system, allowing patterns of input to be characterized and related to population activity throughout the brain.
Results, Conclusions, and Discussions: We discovered that sensory projections display tuning properties distinct from their source and target regions, indicating the importance of local processing in transforming information prior to generating output. We also identified distinct stimulus-dependent response properties among feedforward and feedback projections relating different nodes in the rodent and primate sensory hierarchies. Finally, we determined the extent to which popular linear models could account for population activity in sensory brain regions in terms of their inputs. These studies reveal fundamental aspects of integrated network function in mammalian brains and can inform the interpretation of systems-level neurophysiological data from animals and humans alike.
