MIT Colloquium on Brain & Cognition with Dr. Attila Losonczy
Description
Learning and remembering where and when salient events occur in space and time are essential for adaptive behaviors. Both spatial navigation and episodic memory have been linked to the mammalian hippocampus, but the detailed mechanisms at cellular and circuit levels remain poorly understood. To address these questions, we use in vivo functional imaging to monitor the activity of identified excitatory, inhibitory and neuromodulatory circuit motifs in the hippocampus of behaving mice during spatial exploration, fear learning and goal-directed learning. The talk will focus on our recent efforts aimed at dissecting functional roles of multimodal microcircuits at the dentate gyrus input and at the CA1 output nodes of the hippocampus. I will summarize how various types of dentate gyrus principal neurons – adult-born and mature granule cells, and hilar mossy cells contribute to context encoding and discrimination. We also monitored activity in deep and superficial subpopulations of CA1 pyramidal cells, and assessed the relationship between sublayer dynamics and learning. Finally, I will present findings on how goal-oriented learning is supported by disinhibitory GABAergic circuits in CA1. Together, our results demonstrate a functional division of labor among subpopulations of principal neurons during hippocampal-dependent behaviors.
Speaker Bio
A fundamental capacity of the mammalian cerebral cortex is to process information in a form conducive to encoding, storage and retrieval of memories. A general organizational principle of cortical memory circuits states that these steps all require a precisely orchestrated spatio-temporal interaction among a large number of relatively uniform excitatory and a numerically fewer but richly diverse population of inhibitory and neuromodulatory circuit elements. However, a mechanistic understanding of how these circuit motifs interact during elementary steps of memory processing is lacking. The goal of Attila Losonczy’s laboratory is to study the functional anatomical organization of memory circuits in the rodent hippocampus and to provide a biophysically-based characterization of elementary memory processing and storage mechanisms present in individual neurons. Losonczy uses high-resolution optical and electrophysiological methods together with optogenetic manipulations of specified circuit motifs in vitro, to study how dynamic interactions among excitatory, inhibitory and neuromodulatory inputs in various subcellular domains of neurons underlie information processing and storage in the hippocampal circuit. To link these elementary computations to memory functions, Losonczy applies high-resolution functional imaging in awake mice in vivo. He plan to investigate numerous fundamental questions including: (i) the role of specific spatio-temporal patterns of inhibitory and neuromodulatory inputs in determining neuronal input-output transformations, (ii) the effect of local inhibition and global neuromodulation on the dynamics of subcellular integration and compartmentalization of inputs, and (iii) regulation of various forms of synaptic and intrinsic plasticity by inhibitory and neuromodulatory inputs in the hippocampus.