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Updated: Aug 19, 2026
Generation of Local CA1 γ Oscillations by Tetanic Stimulation
Published on: August 14, 2015
Transient depression of excitatory synapses on interneurons contributes to epileptiform bursts during gamma
Roger D Traub1, Isabel Pais, Andrea Bibbig
1Departments of Physiology and Pharmacology, and Neurology, State University of New York Downstate Medical Center, Brooklyn, NY 11203, USA. roger.traub@downstate.edu
Abstract:
Persistent gamma frequency (30-70 Hz) network oscillations occur in hippocampal slices under conditions of metabotropic glutamate receptor (mGluR) activation. Excessive mGluR activation generated a bistable pattern of network activity during which epochs of gamma oscillations of increasing amplitude were terminated by synchronized bursts and very fast oscillations (>70 Hz). We provide experimental evidence that, during this behavior, pyramidal cell-to-interneuron synaptic depression takes place, occurring spontaneously during the gamma rhythm and associated with the onset of epileptiform bursts. We further provide evidence that excitatory postsynaptic potentials (EPSPs) in pyramidal cells are potentiated during the interburst gamma oscillation. When these two types of synaptic plasticity are incorporated, phenomenologically, into a network model previously shown to account for many features of persistent gamma oscillations, we find that epochs of gamma do indeed alternate with epochs of very fast oscillations and epileptiform bursts. Thus the same neuronal network can generate either gamma oscillations or epileptiform bursts, in a manner depending on the degree of network drive and network-induced fluctuations in synaptic efficacies.
Insights
Persistent gamma oscillations in the hippocampus can switch to epileptiform bursts. This occurs due to synaptic plasticity, specifically depression between pyramidal cells and interneurons, and potentiation of excitatory postsynaptic potentials.
Area of Science:
- Neuroscience
- Computational Neuroscience
- Synaptic Plasticity
Background:
- Persistent gamma frequency (30-70 Hz) network oscillations are observed in hippocampal slices during metabotropic glutamate receptor (mGluR) activation.
- Excessive mGluR activation leads to a bistable network activity pattern, characterized by increasing amplitude gamma oscillations interrupted by synchronized bursts and very fast oscillations (>70 Hz).
Purpose of the Study:
- To investigate the synaptic mechanisms underlying the transition from gamma oscillations to epileptiform bursts.
- To model the role of synaptic plasticity in generating bistable network activity in the hippocampus.
Main Methods:
- Experimental investigation of synaptic plasticity during network oscillations in hippocampal slices.
- Incorporation of observed synaptic plasticity phenomena (synaptic depression and EPSP potentiation) into a computational network model.
Main Results:
- Experimental evidence shows pyramidal cell-to-interneuron synaptic depression occurs spontaneously during gamma rhythms, preceding epileptiform bursts.
- Excitatory postsynaptic potentials (EPSPs) in pyramidal cells are potentiated during the interburst gamma oscillation.
- A network model incorporating these synaptic plasticity rules successfully reproduces the alternating pattern of gamma oscillations and epileptiform bursts.
Conclusions:
- The same neuronal network can generate either gamma oscillations or epileptiform bursts, dependent on network drive and synaptic efficacy fluctuations.
- Synaptic plasticity, including depression and potentiation, plays a critical role in the dynamic switching between oscillatory and burst activity patterns in the hippocampus.
