Mikael Lundqvist
Department of Computational Biology Royal Institute of Technology (KTH), Stockholm, Sweden

Investigating the functional role of nested oscillations in a biophysically-detailed spiking attractor network

Wednesday 03rd of July 2013 at 12:00pm
Evans 560

Nested oscillations, where the phase of the underlying slow rhythm modulates the power of faster oscillations, have recently attracted considerable research attention as the increased phase-coupling of cross-frequency oscillations has been shown to relate to memory processes. Here we investigate the hypothesis that reactivations of memory patterns, induced by either external stimuli or internal dynamics, are manifested as distributed cell assemblies oscillating at gamma-like frequencies with life-times on a theta scale. For this purpose we continue to study a meso-scale attractor memory network model which displays emergent oscillatory dynamics during memory retrieval. We investigate spatial interactions in single frequency bands as well as interactions between distinct frequency components in the synthesized field potential spectra with emphasis on the phenomenon referred to as nesting. A hierarchical nested organization of neural oscillations in theta and gamma frequency bands emerges during memory retrieval. In some conditions the network also displays nested alpha-like oscillations. Despite highly irregular firing during memory retrieval, and random connectivity within each cell assembly, we also observe, as a correlate of oscillatory dynamics, precise spatiotemporal firing patterns that were repeated across memory activations at a rate higher than expected from random firing. In contrast to earlier studies aimed at modeling neural oscillations, our attractor memory network allows us to elaborate on the functional context of emerging rhythms and discuss their relevance. We provide support for the hypothesis that the dynamics of coherent delta/theta oscillations constitute an important aspect of the formation and replay of neuronal assemblies.

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