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Front Neural Circuits. 2014 Jan 31;8:7. doi: 10.3389/fncir.2014.00007. eCollection 2014.

Modulatory effects of inhibition on persistent activity in a cortical microcircuit model.

Author information

1
Department of Biology, University of Crete Heraklion, Greece ; Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology - Hellas Heraklion, Greece.
2
Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology - Hellas Heraklion, Greece.

Abstract

Neocortical network activity is generated through a dynamic balance between excitation, provided by pyramidal neurons, and inhibition, provided by interneurons. Imbalance of the excitation/inhibition ratio has been identified in several neuropsychiatric diseases, such as schizophrenia, autism and epilepsy, which also present with other cognitive deficits and symptoms associated with prefrontal cortical (PFC) dysfunction. We undertook a computational approach to study how changes in the excitation/inhibition balance in a PFC microcircuit model affect the properties of persistent activity, considered the cellular correlate of working memory function in PFC. To this end, we constructed a PFC microcircuit, consisting of pyramidal neuron models and all three different interneuron types: fast-spiking (FS), regular-spiking (RS), and irregular-spiking (IS) interneurons. Persistent activity was induced in the microcircuit model with a stimulus to the proximal apical dendrites of the pyramidal neuron models, and its properties were analyzed, such as the induction profile, the interspike intervals (ISIs) and neuronal synchronicity. Our simulations showed that (a) the induction but not the firing frequency or neuronal synchronicity is modulated by changes in the NMDA-to-AMPA ratio on FS interneuron model, (b) removing or decreasing the FS model input to the pyramidal neuron models greatly limited the biophysical modulation of persistent activity induction, decreased the ISIs and neuronal synchronicity during persistent activity, (c) the induction and firing properties could not be altered by the addition of other inhibitory inputs to the soma (from RS or IS models), and (d) the synchronicity change could be reversed by the addition of other inhibitory inputs to the soma, but beyond the levels of the control network. Thus, generic somatic inhibition acts as a pacemaker of persistent activity and FS specific inhibition modulates the output of the pacemaker.

KEYWORDS:

NMDA; connectivity; fast-spiking interneurons; parvalbumin interneurons; prefrontal cortex; synchronicity

PMID:
24550786
PMCID:
PMC3907788
DOI:
10.3389/fncir.2014.00007
[Indexed for MEDLINE]
Free PMC Article
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