Neuron
Volume 97, Issue 6, 21 March 2018, Pages 1341-1355.e6
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Article
Rapid Rebalancing of Excitation and Inhibition by Cortical Circuitry

https://doi.org/10.1016/j.neuron.2018.01.045Get rights and content
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Highlights

  • Suppressing PV+ cells increased feedforward excitation, which outweighed suppression

  • This led to a paradoxical increase in downstream PV+ spiking

  • PNs thus showed a tightly coordinated increase in both excitation and inhibition

  • This rebalancing constrained PN spiking, producing nonlinear changes in tuning

Summary

Excitation is balanced by inhibition to cortical neurons across a wide range of conditions. To understand how this relationship is maintained, we broadly suppressed the activity of parvalbumin-expressing (PV+) inhibitory neurons and asked how this affected the balance of excitation and inhibition throughout auditory cortex. Activating archaerhodopsin in PV+ neurons effectively suppressed them in layer 4. However, the resulting increase in excitation outweighed Arch suppression and produced a net increase in PV+ activity in downstream layers. Consequently, suppressing PV+ neurons did not reduce inhibition to principal neurons (PNs) but instead resulted in a tightly coordinated increase in both excitation and inhibition. The increase in inhibition constrained the magnitude of PN spiking responses to the increase in excitation and produced nonlinear changes in spike tuning. Excitatory-inhibitory rebalancing is mediated by strong PN-PV+ connectivity within and between layers and is likely engaged during normal cortical operation to ensure balance in downstream neurons.

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