Excitability and Threshold Mechanism for Enhanced Neuronal Response Induced by Inhibition Preceding Excitation

Abstract

Postinhibitory facilitation (PIF) of neural firing presents a paradoxical phenomenon that the inhibitory effect induces enhancement instead of reduction of the firing activity, which plays important roles in sound location of the auditory nervous system, awaited theoretical explanations. In the present paper, excitability and threshold mechanism for the PIF phenomenon is presented in the Morris-Lecar model with type I, II, and III excitabilities. Firstly, compared with the purely excitatory stimulations applied to the steady state, the inhibitory preceding excitatory stimulation to form pairs induces the firing rate increased for type II and III excitabilities instead of type I excitability, when the interval between the inhibitory and excitatory stimulation within each pair is suitable. Secondly, the threshold mechanism for the PIF phenomenon is acquired. For type II and III excitabilities, the inhibitory stimulation induces subthreshold oscillations around the steady state. During the middle and ending phase of the ascending part and the beginning phase of the descending part within a period of the subthreshold oscillations, the threshold to evoke an action potential by an excitatory stimulation becomes weaker, which is the cause for the PIF phenomenon. Last, a theoretical estimation for the range of the interval between the inhibitory and excitatory stimulation for the PIF phenomenon is acquired, which approximates half of the intrinsic period of the subthreshold oscillations for the relatively strong stimulations and becomes narrower for the relatively weak stimulations. The interval for the PIF phenomenon is much shorter for type III excitability, which is closer to the experiment observation, due to the shorter period of the subthreshold oscillations. The results present the excitability and threshold mechanism for the PIF phenomenon, which provide comprehensive and deep explanations to the PIF phenomenon.

Negative self-feedback induced enhancement and transition of spiking activity for class-3 excitability

“…A recent study shows PIF of class-3 neuron, where inhibition preceding excitation can promote the membrane potential to the threshold of action potential, but whether inhibition can induce the PIR spike is unknown. [53] In this study, the PIR spike is identified to be elicited for class-3 excitability that is far from the bifurcation point, which extends the condition for the PIR spikes. This result is consistent with an electrophysiology experiment wherein the PIR spike can be induced in phasic spiking neurons [8] such as caudal mesopallium neurons.…”

“…[23,52] Recently, the PIF phenomenon has been simulated for both class-2 excitability and class-3 excitability. [19,53] Compared with class-2 excitability, there are fewer reports about the PIR spike and enhancement of spiking activity induced by the inhibitory effect for class-3 neurons. [7,8] In this study, the effects of an inhibitory autapse with time delay on dynamical behaviors of the Morris-Lecar (ML) neuron with class-3 excitability are investigated.…”

Predicting the Influence of Axon Myelination on Sound Localization Precision Using a Spiking Neural Network Model of Auditory Brainstem

“…First, a low-threshold potassium current shown to interact with the synaptic inhibition in MSO and sharpen the temporal sensitivity of the binaural integration ( Khurana et al, 2011 ; Roberts et al, 2013 ; Myoga et al, 2014 ) was omitted. Second, post-inhibitory facilitation that can raise the firing rate under certain conditions ( Beiderbeck et al, 2018 ; Ma et al, 2021 ) and had been observed in the MSO of juvenile mice ( Dodla et al, 2006 ) was also not considered. This phenomenon could possibly compensate for a decreased firing rate induced by the leading contralateral inhibition in MSO.…”

Predicting the Influence of Axon Myelination on Sound Localization Precision Using a Spiking Neural Network Model of Auditory Brainstem

“…First, a low-threshold potassium current shown to interact with the synaptic inhibition in MSO and sharpen the temporal sensitivity of the binaural integration (Khurana et al, 2011;Roberts et al, 2013;Myoga et al, 2014) was omitted. Furthermore, post-inhibitory facilitation that can raise the firing rate under certain conditions (Beiderbeck et al, 2018;Ma et al, 2021) and had been observed in the MSO of juvenile mice (Dodla et al, 2006) was also not considered. This phenomenon could possibly compensate for a decreased firing rate induced by the leading contralateral inhibition in MSO.…”