Understanding Circuits

CRCNS US-German Research Proposal: Quantitative and computational dissection of glutamatergic crosstalk at tripartite synapses (1) Christine R Rose, Heinrich Heine University, Düsseldorf, Germany (2) Christian Henneberger, University of Bonn, Germany (3) Ghanim Ullah, University of South Florida, Tampa, FL, USA Project Description 1 Introduction and Background Transmission at chemical synapses is the central mechanism by which information is transferred between neurons.

Project Summary/Abstract Neural representations supporting spatial and episodic learning form, and transform rapidly in the mammalian hippocampus. Individual hippocampal pyramidal cells each fire at a specific location in an environment and together these place cells provide a striking substrate for a cognitive map. A critical step in achieving a mechanistic understanding of how place cell dynamics support hippocampal learning and memory is to be able to re-create endogenous neuronal representations experimentally, and test their behavioral relevance.

PROJECT SUMMARY The insular cortex (IC) is a multimodal hub that integrates interoceptive and exteroceptive information to control diverse aspects of animal behaviors related to cognition, emotion, and motivation. Among other functions, the IC receives information regarding an animal’s metabolic states and drives motivation and valence-specific behaviors. However, our understanding of the neuronal substrates and circuit principles underlying IC function is still in its infancy.

Cortical assembly formation through excitatory/inhibitory circuit plasticity. Project Summary Throughout the brain, sensory information is thought to be represented by the joint activity of neurons that form functionally connected assemblies. A long-standing premise is that assemblies are formed during sensory learn- ing by strengthening the excitatory connections between co-active neurons. However, the role of inhibition in this process has yet to be fully elucidated.

PROJECT SUMMARY Within every brain region, neurons can be classified into dozens or hundreds of different cell types, each with unique functional roles and unique impacts on disease states. Traditionally, in vivo electrophysiological recordings—which have made invaluable contributions to our understanding of the neural basis of behavior— have not been able to distinguish the activity of genetically defined cell types.

PROJECT SUMMARY/ABSTRACT Because neurons integrate and process information via modulation of their membrane potential, the ability to monitor voltage is critical to understanding how single and groups of neurons compute. Genetically encoded voltage indicators (GEVIs) —fluorescent proteins that report voltage dynamics as changes in brightness— are emerging as a preferred recording method because they can track voltage transients with high spatiotemporal resolution and cell type specificity.