EVENT DETAILS AND ABSTRACT

Title: Mean theta phase of model CA1 pyramidal cell firing changes with location of synaptic stimuli
Speaker: Victoria Booth
Speaker Info: University of Michigan
Brief Description:
Special Note: More current information may be available at Plan-it Purple
Abstract:

In recordings from rat hippocampal CA1 place cells during learning and subsequent sleep episodes, Poe et al (2000) observed changes in place cell activity during REM reactivation that correlated with experience and followed the course of memory consolidation. The mean phase of place cell firing in relation to the theta rhythm membrane oscillation reversed during REM reactivation over the course of several days as the animal became familiar with the environment. Cells with place fields in an initially novel environment switched from firing near the theta rhythm peaks to firing near the theta troughs during REM while maintaining their theta peak activity during waking exploration. Theta trough firing during REM may uniquely facilitate depotentiation of intra- hippocampal synapses which are associated with now familiar, cortically- consolidated memories and allow for learning of new information and the integration of novel information with old memories. In a computational modeling study, we investigated neural mechanisms underlying experience- dependent theta phase reversal by incorporating the differential in the phase of the theta rhythm drive at the two excitatory afferent pathways to CA1 and testing model CA1 cell responses to inputs at these two paths. We will discuss simulation results that show that firing in response to proximal, Schaffer collateral synaptic input occurs preferentially near the peaks of the theta membrane oscillation while firing in response to distal dendritic, temporo-ammonic synaptic input occurs near the theta troughs. These results support the hypothesis that the gradual shift to theta trough firing would result from a growing potentiation of synapses in the direct, temporo-ammonic pat