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The rectification of an electrical synapse can change the functional output of a pattern-generating circuit
BMC Neuroscience volume 14, Article number: P259 (2013)
Electrical synapses are known to promote synchrony and speed in neuronal systems. However, other studies have found that electrical synapses can have the opposite effect by desynchronizing network neurons. Although they are mechanistically simple, electrical synapses can have unintuitive effects on neuronal network activity. The present study aims to further our understanding of electrical synapses by exploring their rectification in a neuronal circuit model. Rectification is the asymmetrical passage of current through a gap junction between two neurons and it is often likened to a diode in an electrical circuit. Rectifying electrical synapses have been shown to support specialized functions in several biological preparations . We investigate how rectification affects the functional output of a 5-cell, pattern-generating, model network and its sensitivity to synaptic modulation. The circuit is composed of heterogeneous neurons with different intrinsic oscillation frequencies. Neurons were modeled as Morris-Lecar  neurons modified by a hyperpolarization-activated current as in a previous study .
We find that circuit output depends on the polarity and placement of the rectifying electrical synapse and the intrinsic properties of the neurons on either side of it (Figure 1). Furthermore, using the parameterscape visualization method , we find that rectification can affect the circuit's sensitivity to modulation of synaptic strength - including modulation of chemical synapse strength. This can have a dramatic effect on the functional output of a pattern-generating circuit. For a multi-functional motor network, it is important to be able to switch between stable network patterns by synaptic neuromodulation. However, our results show that some kinds of electrical synapse rectification can switch off multi-functionality even when there are degenerate synaptic pathways. In conclusion, these results demonstrate how a rectifying electrical synapse has the potential to specialize a neuronal circuit for robust output or for flexibility.
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Morris C, Lecar H: Voltage oscillations in the barnacle giant muscle fiber. Biophysical Journal. 1981, 35 (1): 193-213. 10.1016/S0006-3495(81)84782-0.
Gutierrez GJ, O'Leary T, Marder E: Multiple mechanisms switch an electrically coupled, synaptically inhibited neuron between competing rhythmic oscillators. Neuron. 2013
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Gutierrez, G.J., Marder, E. The rectification of an electrical synapse can change the functional output of a pattern-generating circuit. BMC Neurosci 14, P259 (2013) doi:10.1186/1471-2202-14-S1-P259
- Neuronal Circuit
- Synaptic Strength
- Motor Network
- Circuit Output
- Chemical Synapse