Cosyne 2007 Workshops
February 26-27, 2007
The Canyons, Utah
George Dragoi
Oscillatory binding of place sequences by hippocampal cell assemblies
Among the most remarkable features of a memory episode are the sequential order of composing events and their fine spatial-temporal relationship that binds them together into a unique episode. Similar to episodic learning of serial events, sequential activation of hippocampal place cells on a track is believed to produce a representation that binds past, present, and future locations into a “spatial episode”. We showed that compressed spatial sequences were recurrently represented for several theta cycles by the temporally coordinated activity of hippocampal cell assemblies. The temporal correlation between place cell pairs was stronger than predicted by a pacemaker drive of independent neurons and varied in strength within the theta cycle. This indicates a critical role for synaptic interactions and precise timing within and across cell assemblies in sequence representation. CA1 and CA3 ensembles, identifying spatial locations, were active preferentially on the opposite phases of the theta cycles. These observations suggest that interleaving CA3 neuronal sequences bind CA1 assemblies representing overlapping past, present and future locations into single episodes.
