Autaptic connections and synaptic depression constrain and promote gamma oscillations

Abstract

Computational models of gamma oscillations have helped increase our understanding of the mechanisms that shape these 40-80 Hz cortical rhythms. Evidence suggests that interneurons known as basket cells are responsible for the generation of gamma oscillations. However, current models of gamma oscillations lack the dynamic short term synaptic plasticity seen at basket cell-basket cell synapses as well as the large autaptic synapses basket cells are known to express. Hence, I sought to extend the Wang-Buzsáki model of gamma oscillations to include these features. I found that autapses increased the synchrony of basket cell membrane potentials across the network during neocortical gamma oscillations as well as allowed the network to oscillate over a broader range of depolarizing drive. I also found that including realistic synaptic depression filtered the output of the network. Depression restricted the network to oscillate in the 60-80 Hz range rather than the 40- 120 Hz range seen in the standard model. This work shows the importance of including accurate synapses in any future model of gamma oscillations. © 2014 William M. Connelly.