Brownian Optogenetic-Noise-Photostimulation on the Brain Amplifies Somatosensory-Evoked Field Potentials

Abstract

Stochastic resonance (SR) is an inherent and counter-intuitive mechanism of signal-to-noise ratio (SNR) facilitation in biological systems associated with the application of an intermediate level of noise. As a first step to investigate in detail this phenomenon in the somatosensory system, here we examined whether the direct application of noisy light on pyramidal neurons from the mouse-barrel cortex expressing a light-gated channel channelrhodopsin-2 (ChR2) can produce facilitation in somatosensory evoked field potentials. Using anesthetized Thy1-ChR2-YFP transgenic mice, and a new neural technology, that we called Brownian optogenetic-noise-photostimulation (BONP), we provide evidence for how BONP directly applied on the barrel cortex modulates the SNR in the amplitude of whisker-evoked field potentials (whisker-EFP). In all transgenic mice, we found that the SNR in the amplitude of whisker-EFP (at 30% of the maximal whisker-EFP) exhibited an inverted U-like shape as a function of the BONP level. As a control, we also applied the same experimental paradigm, but in wild-type mice, as expected, we did not find any facilitation effects. Our results show that the application of an intermediate intensity of BONP on the barrel cortex of ChR2 transgenic mice amplifies the SNR of somatosensory whisker-EFPs. This result may be relevant to explain the improvements found in sensory detection in humans produced by the application of transcranial-random-noise-stimulation (tRNS) on the scalp.

Noisy Light Augments the Na+ Current in Somatosensory Pyramidal Neurons of Optogenetic Transgenic Mice

“…Our results are consistent with the idea that an inherent action of random noise is related to the observed augmentation-effects, thus in line with the previous hypothesis claiming that the stochastic resonance is an inherent property of rate-modulated random series of events (Bezrukov, 1998). Our results provide support to previous observations, claiming that the short-duration BONP on the barrel cortex of ChR2 transgenic mice can increase the evoked field potentials and the firing frequency response of pyramidal neurons to somatosensory mechanical stimulation (Huidobro et al, 2017(Huidobro et al, , 2018. Finally, to exclude an optonongenetic effect due to temperature changes induced by the delivered light (Ait Ouares et al, 2019;Ghirga et al, 2020) we examined whether our intensities of BONP up to 0.67 mW produce similar effects in wild type mice.…”

“…It means that an intermediate level of BONP can increase the peak amplitude of the Na + inward current and its inverse of latency of pyramidal neurons from the somatosensory cortex elicited by voltage-clamp microstimulation. The technique employed in the present article was based on two previous studies from our laboratory, in which we introduced a new type of brain stimulation with noisy light, termed BONP (Huidobro et al, 2017;Huidobro et al, 2018). Both studies provided support to the findings of the present article.…”

“…The BONP stimulus exhibited a flashing-like behavior with random fluctuations in the intensities of light. The power spectrum of this light was Brownian in the frequency range from 0 to 5,000 Hz (see power spectrum of BONP in previous studies, Huidobro et al, 2017Huidobro et al, , 2018. The optical power of the blue light was measured with an optical power meter PM100D and sensor S150C from Thorlabs.…”

Stochastic resonance enhances the rate of evidence accumulation during combined brain stimulation and perceptual decision-making

“…Recently, animal work has shown that optogenetic-noise-photostimulation of the barrel cortex in mice enhances both evoked-field and spike-firing responses to mechanical stimulation of the whiskers [ 54 , 55 ]. Optogenetic-noise-photostimulation could be used in combination with a decision task in mice [ 56 ] to further investigate the mechanism underlying our observed behavioral effect in human perceptual-decision making.…”

When the Ostrich-Algorithm Fails: Blanking Method Affects Spike Train Statistics

“…In laboratory settings, where the mechanism of action is being explored, alternative stimulation modalities such as optogenetic stimulation can be used, even at high frequencies, to examine the effects on firing rates (Deisseroth, 2015 ; Huidobro et al, 2017 , 2018 ). However, even this modality comes with its own difficulties and traps (Ayling et al, 2009 ; Cardin et al, 2009 ; Han et al, 2009 ).…”