Zelman Center Seminar - Dr. Yoav Adam - All-optical Dissection of hippocampal circuits using voltage imaging
Abstract: Hippocampal place cells form a cognitive map of space. My lab studies the role of the local hippocampal microcircuit in place cell formation and stabilization. We use a combination of genetically encoded voltage indicators, holographic illumination, and high-speed microscopes that enable in vivo recordings of supra- and subthreshold voltage dynamics in behaving mice. In this talk, I will describe the technology and present two stories in which we study the interplay of excitation and inhibition in CA1 during behavior. First, by combining voltage imaging with orthogonal optogenetic modulation, we recorded the intracellular dynamics and F-I curves of 4 major hippocampal cell types. We revealed behavioral state-dependent modulation of local network firing patterns, subthreshold oscillatory activity, and neuronal gain. Second, we recorded the intracellular activity of CA1 pyramidal cells and Somatostatin-positive (SST) interneurons during spatial navigation in familiar and novel virtual environments. Repeated imaging in familiar spaces revealed stable and dynamic tuning properties in the intracellular activity of both cell types. Transition to a novel space induced remapping as well as an increase in the global firing of the SST cells. Overall, these studies deepen our understanding of hippocampal microcircuit dynamics and plasticity during spatial navigation and highlight the new prospects opened by recently developed voltage imaging technology.
