The Bernstein Center for Computational Neuroscience Freiburg

Announcement for the next
Informal Seminar
Omar Ahmed
Department of Neuroscience
Brown University
Providence, RI, USA

Mechanisms and Functions of the Hippocampal Temporal Code:
In Vivo, In Silico, In Vitro

Monday, September 29th, 2008
17:00 h TIME
Lecture Hall
Bernstein Center
Hansastr. 9a
Cells in the rodent hippocampus show spatial selectivity and hence are called place cells. The activity of a place cell within its place field shows a prominent temporal code known as phase precession. The spikes from these cells occur in a coordinated manner with respect to the ongoing theta rhythm that arises in the septo-hippocampal system during active exploration. As a rat enters the place field of a cell, the cell fires late in the first theta cycle. The phase of the spikes with respect to theta steadily precess to earlier values in subsequent theta cycles, eventually precessing by almost 360 degrees as the rat reaches the end of the place field. The phase of the spikes is better correlated with position than with time, as differences in the rat's velocity do not alter the phase precession curve. It remains unclear how this temporal code is generated. Using a combination of in vivo tetrode recordings, in vitro dynamic clamp experiments and computational modeling we show how a simple rate based combination of inhibitory and excitatory inputs can give rise to all the properties of phase precession. We also show that hippocampal phase precession can only be inherited from entorhinal cortical grid cells under a restricted set of conditions.
The talk is open to the public. Guests are cordially invited!