Further information
Dr Jozsef Csicsvari, MRC Anatomical Neuropharmacology Unit, University of Oxford presents this seminar.
Abstract: The hippocampus is involved in the formation of spatial and episodic memories, and hippocampal pyramidal cells fire in relation to space. Cells with similar spatially-selective firing fields (place fields) tend to fire together in subsequent sleep, suggesting that place cells encoding similar places form cell assemblies for reactivation. Such ‘reactivation’ is thought to be involved in the consolidation of episodic memories.
Here we examined the formation of reactivated cell assemblies by measuring changes in CA1 pyramidal cell firing-associations between sleep sessions before and after exploration. The largest increases in firing-association occurred between cells representing the most visited regions of the environment. These increases were also dependent on the number of times the cells fired together with short latencies during exploration. The largest increases were seen between cells firing <50 ms apart. Moreover, cell pairs with non-overlapping fields, which tended to fire independently, showed a reduction in association strength proportional to the amount of independent firing. We propose that reactivated cell assemblies are formed through Hebbian increases in firing-association, and are shaped by negative changes. Our results also provide evidence that reactivated patterns are determined by recent behaviour. Such experience-dependent replay may point to the recurrence of episodic-like memory traces.
Biography: Dr. Jozsef Csicsvari graduated in Informatics at the Technical University of Budapest, Hungary, in 1993. He then went to Rutgers University, USA, to study for his Ph.D. in Neuroscience under the supervision of Professor Gyorgy Buzsaki. Following the award of his Ph.D. in 1999, he remained in the laboratory of Prof. Buzsaki and continued with postdoctoral training between1999-2002. In January 2003, he joined the MRC Anatomical Neuropharmacology Unit as a group leader. His research interest has been to study oscillatory activity in the brain, and to understand the behavioural role and physiological mechanism of these oscillations in the hippocampus and other cortical areas.
Light refreshments served from 3.30pm in the Staff Breakout Room, Room 3.24, Royal School of Mines.