Biopsychology 

Prof. Michael Hasselmo, Department of Psychology, Boston University

Tuesday, November 10, 2009, 12:00 pm – 1:00 pm
4448 East Hall

Event Information

ABSTRACT

Recent slice physiology, unit recording and computational modeling demonstrate the potential role in memory function of oscillatory dynamics and persistent firing in entorhinal cortex neurons.  Whole cell patch data from my laboratory shows that neurons have higher frequencies of resonance and membrane potential oscillations in dorsal compared to ventral entorhinal cortex (Giocomo et al., 2007; Giocomo and Hasselmo, 2008).  This data scales with the spacing between firing fields of entorhinal grid cells, which fire in a hexagonal array of locations as a rat explores the environment. The scaling of frequency to grid cell spacing provides experimental support for a model of grid cell firing by Burgess, Barry and O’Keefe in which interference between oscillations generates realistic grid cell spiking activity in a virtual rat.  Mechanisms for stable persistent firing of entorhinal neurons (Yoshida et al., 2008) may also underlie grid cell firing patterns (Hasselmo, 2008b) and could provide mechanisms for active maintenance for memory encoding (Hasselmo and Stern, 2006).  Grid cell models incorporated in a network model of episodic memory function allow accurate encoding and retrieval of spatiotemporal trajectories (Hasselmo, 2008a), using interactions with place cells and persistent spiking head direction cells (Yoshida and Hasselmo, 2009).  These models can replicate data on the context-dependent firing of neurons in a spatial alternation task (Lee et al., 2006) and the temporally structured replay of previously experienced episodes during sleep (Hasselmo, 2008a), and provide a potential neural mechanism for episodic memory and mental time travel in humans. 

Giocomo, L.M., Hasselmo, M.E. (2008) Time constant of I(h) differs along dorsal to ventral axis of medial entorhinal cortex. J. Neurosci., 28:9414-25

Giocomo LM, Zilli EA, Fransen E, Hasselmo ME. (2007) Temporal frequency of subthreshold oscillations scales with entorhinal grid cell field spacing. Science, 315:1719-22.

Hasselmo, M.E. (2008a) Temporally structured replay of neural activity in a model of entorhinal cortex, hippocampus and postsubiculum. Eur. J. Neurosci. 28:1301-1315

 

Hasselmo M.E. (2008b) Grid cell mechanisms and function: Contributions of entorhinal persistent spiking and phase resetting. Hippocampus. 2008;18(12):1213-29.

 Hasselmo, M.E., Stern, C.E. (2006) Mechanisms underlying working memory for novel information. Trends in Cognitive Sciences, 10(11):487-93.

 Lee I, Griffin AL, Zilli EA, Eichenbaum H, Hasselmo ME (2006) Gradual translocation of spatial correlates of neuronal firing in the hippocampus toward prospective reward locations. Neuron, 51: 639-50.

 Yoshida, M., Fransen, E., Hasselmo, M.E. (2008) mGluR-dependent persistent firing in entorhinal cortex layer III neurons. Eur. J. Neurosci. 28(6):1116-26.

 Yoshida M., Hasselmo M.E. (2009) Persistent firing supported by an intrinsic cellular mechanism in a component of the head direction system. J Neurosci. 29(15):4945-52.

For More Information

Website URL: http://www.bu.edu/hasselmo