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Tuning in the Hippocampal Theta Band In Vitro: Methodologies for Recording from the Isolated Rodent Septohippocampal Circuit
Published on: August 2, 2017
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On phasic inhibition during hippocampal theta.
Bruce P Graham1, Emiliano Spera
1Computing Science & Mathematics, School of Natural Science, University of Stirling , Scotland , UK.
Network (Bristol, England)
|February 28, 2014
Summary
Computational models reveal how distinct patterns of inhibition during theta oscillations in the hippocampus may enable distinct memory phases. This suggests a flexible mechanism for encoding and recall in rodent brains.
Area of Science:
- Computational neuroscience
- Systems neuroscience
- Neurobiology of learning and memory
Background:
- Theta frequency (4-10 Hz) oscillations are crucial for hippocampal function in rodents.
- A prevailing hypothesis suggests theta cycles are divided into encoding and recall phases.
- Synaptic plasticity, particularly long-term potentiation (LTP), is thought to be enhanced during encoding and suppressed during recall.
Purpose of the Study:
- To computationally explore the role of phasic inhibition in creating distinct encoding and recall phases during hippocampal theta oscillations.
- To investigate how different types of inhibition (perisomatic vs. dendritic) influence synaptic plasticity and neuronal output.
- To interpret recent experimental data on hippocampal activity during rodent navigation.
Main Methods:
- Utilized a compartmental model of a CA1 pyramidal neuron, incorporating dendritic spines.
- Employed a second model based on the sum-of-sinusoids to analyze neural activity patterns.
- Simulated the effects of out-of-phase perisomatic and dendritic inhibition on neuronal dynamics.
Main Results:
- Demonstrated that out-of-phase perisomatic and dendritic inhibition can establish conditions for distinct encoding and recall half-cycles.
- Showed that perisomatic inhibition facilitates dendritic calcium spikes for LTP while minimizing output.
- Indicated that dendritic inhibition controls output and suppresses calcium spikes, thereby preventing LTP.
- Proposed that the phase relationship between these sub-cycles may be flexible, with recall cycles adapting to excitatory drive.
Conclusions:
- Phasic inhibition provides a mechanism to segregate encoding and recall processes within hippocampal theta cycles.
- A flexible recall phase, following excitatory drive and phase precession, may be a key feature of memory processing in spatial navigation.
- Computational modeling offers valuable insights into the dynamic interplay of inhibition and plasticity in the hippocampus.
