George Dragoi
George Dragoi, MD, PhD
Assistant Professor of Psychiatry and of Neuroscience
Neuronal ensembles underlying internal representations
Abstract
Internal representations about the external world can be driven by the external stimuli or can be internally generated in their absence. It has been a matter of debate whether novel stimuli from the external world are instructive over the brain network to create de novo representations or, alternatively, are selecting from existing pre-representations hosted in preconfigured brain networks. The hippocampus is a brain area necessary for normal internally generated spatial-temporal representations and its dysfunctions have resulted in anterograde amnesia, impaired imagining of new experiences, and hallucinations. The compressed temporal sequence of place cell activity in the rodent hippocampus serves as an animal model of internal representation of the external space. Our recent results on the phenomenon of novel place cell sequence preplay, have shown that the place cell sequence of a novel spatial experience is determined, in part, by a selection of a set of cellular firing sequences from a repertoire of existing temporal firing sequences in the hippocampal network. Conceptually, this indicates that novel stimuli from the external world select from their pre-representations rather than create de novo our internal representations of the world.
Author
Dr. George Dragoi is Assistant Professor of Psychiatry and of Neuroscience in the Department of Psychiatry at Yale University School of Medicine in New Haven, CT.
He graduated Special Education at Alexandru Ioan Cuza University of Iasi, Romania. Also, he holds M.D. degree from the Gr. T. Popa University of Medicine and Pharmacy of Iasi, Romania and Ph.D. degree in Behavioral and Neural Science from Rutgers University where he worked in the laboratory of Dr. GyorgyBuzsaki. He completed his postdoctoral studies at the Picower Institute for Learning and Memory at the Massachusetts Institute of Technology in the laboratory of Dr. Susumu Tonegawa.
Dr. Dragoi studies the neurophysiological basis of the organization of hippocampal neurons into cellular assemblies and their dynamic grouping during novel spatial exploration and in response to long-term synaptic plasticity. Recently, he revealed the existence of preconfigured cellular assemblies that pre-play in time the spatial sequences occurring during a future novel spatial experience in naive animals.
Dr. Dragoi’ current research focuses on the role of neuronal activity and prior experience in cellular assembly organization and animal learning with implications for our better understanding of neuropsychiatric diseases.
Welcome to the Dragoi Lab
Our cognitive life depends on our ability to generate internal representations of the external world. Internal representations can be driven by the external stimuli (e.g., perceptions) or can be internally-generated in their absence (e.g., imagining, memory). The dynamic interplay between externally-driven and internally-generated representations is thought to be disrupted in neuropsychiatric conditions such as schizophrenia, autism, and Alzheimer’s disease. The long-term goal of the lab is to map and dissect the neural circuits and decipher the neuronal codes underlying the formation of internal representations within hippocampal-neocortical networks that support innate and learned behavior, with implications for our understanding of neuropsychiatric diseases.
Learned information is not encoded in isolation, but is integrated within a network of preexisting knowledge stored in patterns of neuronal ensemble functional connectivity. Our immediate goal is to investigate:
- How these patterns emerge and develop
- How are they utilized in behavior
- How are they disrupted in neuropsychiatric diseases
The hippocampus, a brain structure initially implicated in rapid learning and formation of episodic memory, is now recognized to encode internally-generated spatial-temporal sequence representations. Its dysfunctions have resulted in anterograde amnesia, impaired imagining of new experiences, and hallucinations. Achieving our goal will be facilitated by our use of electrophysiological recordings of ensembles of neurons in behaving mice and rats, optogenetic manipulation of neurons, optical imaging of neuronal ensembles, and computational methods for decoding neuronal population activity.
Welcome to the Dragoi Lab
