Slow N-Methyl-D-aspartic acid (NMDA) synaptic currents are assumed to strongly contribute to the persistently elevated firing rates observed in prefrontal cortex (PFC) during working memory. During persistent activity, spiking of many neurons is highly irregular. ... The highest interspike-interval (ISI) variability occurred in a transition regime where the subthreshold membrane potential distribution shifts from mono- to bimodality, ... Predictability within irregular ISI series was significantly higher than expected from a noise-driven linear process, indicating that it might best be described through complex (potentially chaotic) nonlinear deterministic processes. Accordingly, the phenomena observed in vitro could be reproduced in purely deterministic biophysical model neurons. High spiking irregularity in these models emerged within a chaotic, close-to-bifurcation regime characterized by a shift of the membrane potential distribution from mono- to bimodality and by similar ISI return maps as observed in vitro. ... NMDA-induced irregular dynamics may have important implications for computational processes during working memory and neural coding.
Model Type: Realistic Network
Region(s) or Organism(s): Neocortex; Prefrontal cortex (PFC)
Cell Type(s): Neocortex L5/6 pyramidal GLU cell
Currents: I Na,p; I Na,t; I L high threshold; I K; I Potassium
Model Concept(s): Activity Patterns; Working memory; Calcium dynamics; Bifurcation
Simulation Environment: NEURON; MATLAB
Implementer(s): Durstewitz, Daniel [daniel.durstewitz at plymouth.ac.uk]
References:
Durstewitz D, Gabriel T. (2007). Dynamical basis of irregular spiking in NMDA-driven prefrontal cortex neurons. Cerebral cortex (New York, N.Y. : 1991). 17 [PubMed]