Systems Neuroscience

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.

In natural vision, recognizing objects based on the retinal image is challenging and is often an ill-posed problem because a single image is compatible with multiple interpretations. Nevertheless, the primate brain has a remarkable ability to understand ambiguous scenes and solve difficult object recognition problems. Converging evidence suggests that this process, especially in challenging contexts—e.g., occlusion or low-visibility environments—is based on the integration of sensory information with prior knowledge built from experience.

PROJECT SUMMARY/ABSTRACT An important longstanding goal in neuroscience research is to understand how large-scale spatiotemporal patterns of neural activity emerge in the brain and whether they have a direct role in shaping the brain’s computational processes and thereby mammalian behavior.

SUMMARY Norepinephrine (NE) is a neurotransmitter released by a small number of neurons in the locus coeruleus (LC), with extensive innervation of the neocortex. Prior work in humans and other mammals led to the hypothesis that LC-NE neurons modulate multiple forms of decision making. This proposal aims to test this overall hypothesis by studying LC-NE neurons in mice performing multiple decision-making tasks.

PROJECT SUMMARY Serotonin is an evolutionarily conserved neurotransmitter that modulates the activity of excitatory and inhibitory neurons throughout the entire mammalian brain and is thus essential for diverse aspects of physiology and behavior. Drugs that impact the serotonin system have been used to treat numerous brain disorders including depression, anxiety, and post-traumatic stress disorder. In the mammalian brain, serotonin neurons are clustered in the raphe nuclei of the brainstem, but project axons across the entire brain.

PROJECT SUMMARY/ABSTRACT Effective interpretation of sensory stimuli relies on the ability to discriminate stimulus features and link them to appropriate behavioral responses depending on past experience. Much remains unknown, however, about the roles that different neural pathways play in representing and learning these associations, and in particular, how information is distributed and combined among different pathways during learning and execution of behavior.