Auditory Noise Facilitates Lower Visual Reaction Times in Humans.

Noise is commonly seen as a disturbance but can influence any system it interacts with. This influence may not always be desirable, but sometimes it can improve the system's performance. For example, stochastic resonance is a phenomenon where adding the right amount of noise to a weak signal makes it easier to detect. This is known as sub-threshold detection. This sub-threshold detection's natural fingerprint is the fact that the threshold values follow an inverse U-shaped curve as the noise intensity increases. The minimum threshold value is the point of maximum sensitivity and represents the optimal point that divides the dynamics in two. Below that point, we can find the beneficial noise branch, where the noise can facilitate better detection. Above that point, the common detrimental noise concept can be found: adding noise hinders signal detection. The nervous system controls the movements and bodily functions in the human body. By reducing the sensory thresholds, we can improve the balance of these functions. Additionally, researchers have wondered if noise could be applied to different senses or motor mechanisms to enhance our abilities. In this work, noise is used to improve human reaction times. We tested the hypothesis that visual reaction times decrease significantly when the subject's perception is in the beneficial noise branch and closer to the optimal point than outside of this condition. Auditory noise was introduced in 101 human subjects using an interface capable of searching for the right amount of noise to place the subject in the beneficial noise branch close to the optimal point. When comparing the results, the reaction times decreased when the subjects were at the optimal point compared to when the subjects were outside of such conditions. These results reveal the possibility of using this approach to enhance human performance in tasks requiring faster reaction times, such as sports.

Contrarian Majority Rule Model with External Oscillating Propaganda and Individual Inertias.

We study the Galam majority rule dynamics with contrarian behavior and an oscillating external propaganda in a population of agents that can adopt one of two possible opinions. In an iteration step, a random agent interacts with three other random agents and takes the majority opinion among the agents with probability p(t) (majority behavior) or the opposite opinion with probability 1-p(t) (contrarian behavior). The probability of following the majority rule p(t) varies with the temperature T and is coupled to a time-dependent oscillating field that mimics a mass media propaganda, in a way that agents are more likely to adopt the majority opinion when it is aligned with the sign of the field. We investigate the dynamics of this model on a complete graph and find various regimes as T is varied. A transition temperature Tc separates a bimodal oscillatory regime for TTc in which m oscillates around zero. These regimes are characterized by the distribution of residence times that exhibit a unique peak for a resonance temperature T*, where the response of the system is maximum. An insight into these results is given by a mean-field approach, which also shows that T* and Tc are closely related.

Contrarian Voter Model under the Influence of an Oscillating Propaganda: Consensus, Bimodal Behavior and Stochastic Resonance.

We study the contrarian voter model for opinion formation in a society under the influence of an external oscillating propaganda and stochastic noise. Each agent of the population can hold one of two possible opinions on a given issue­against or in favor­and interacts with its neighbors following either an imitation dynamics (voter behavior) or an anti-alignment dynamics (contrarian behavior): each agent adopts the opinion of a random neighbor with a time-dependent probability p(t), or takes the opposite opinion with probability 1−p(t). The imitation probability p(t) is controlled by the social temperature T, and varies in time according to a periodic field that mimics the influence of an external propaganda, so that a voter is more prone to adopt an opinion aligned with the field. We simulate the model in complete graph and in lattices, and find that the system exhibits a rich variety of behaviors as T is varied: opinion consensus for T=0, a bimodal behavior for TTc, and full disorder for T≫1. The transition temperature Tc vanishes with the population size N as Tc≃2/lnN in complete graph. In addition, the distribution of residence times tr in the bimodal phase decays approximately as tr−3/2. Within the oscillatory regime, we find a stochastic resonance-like phenomenon at a given temperature T*. Furthermore, mean-field analytical results show that the opinion oscillations reach a maximum amplitude at an intermediate temperature, and that exhibit a lag with respect to the field that decreases with T.

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

In previous reports, we developed a method to apply Brownian optogenetic noise-photostimulation (BONP, 470 nm) up to 0.67 mW on the barrel cortex of in vivo ChR2 transgenic mice. In such studies, we found that the BONP produces an increase in the evoked field potentials and the neuronal responses of pyramidal neurons induced by somatosensory mechanical stimulation. Here we extended such findings by examining whether the same type of BONP augments the Na+ current amplitude elicited by voltage-clamp ramps of dissociated pyramidal neurons from the somatosensory cortex of ChR2 transgenic and wild type mice. We found that in all neurons from the ChR2 transgenic mice, but none of the wild type mice, the peak amplitude of a TTX-sensitive Na+ current and its inverse of latency exhibited inverted U-like graphs as a function of the BONP level. It means that an intermediate level of BONP increases both the peak amplitude of the Na+ current and its inverse of latency. Our research suggests that the impact of BONP on the Na+ channels of pyramidal neurons could be associated with the observed augmentation-effects in our previous in vivo preparation. Moreover, it provides caution information for the use of an appropriate range of light intensity, <0.67 mW, which could avoid opto non-genetics (also termed "optonongenetic") related responses due to light-induced temperature changes.

Augmenting Global Coherence in EEG Signals with Binaural or Monaural Noises.

Internal stochastic resonance (internal SR) is a phenomenon of non-linear systems in which the addition of a non-zero level of noise produces an enhancement in the coherence between two or more signals. In a previous study, we found that the simultaneous administration of multisensory visual and auditory noise augments global coherence in electroencephalographic (EEG) signals via this phenomenon. Here, we examined whether such global coherence can also be augmented with at least one noisy acoustic source. We performed experiments on healthy subjects and applied the following binaural and monaural noise-stimulation protocols. First, we administered to the left ear Gaussian noise of fixed intensity, while we delivered to the right ear a second Gaussian noise of variable intensity levels (binaural protocol). Second, we applied the Gaussian noise of the same variable intensity levels but only to one ear (monaural protocol). We performed a permutation test analysis, finding that during both noise protocols there was a significant enhancement in the global coherence in EEG signals via the occurrence of internal SR within central pathways of the auditory system.

Effects of Short-Term Random Noise Electrical Stimulation on Dissociated Pyramidal Neurons from the Cerebral Cortex.

Transcranial random noise electrical stimulation (tRNS) of the human brain is a non-invasive technique that can be employed to increase the excitability of the cerebral cortex; however, the physiological mechanisms remain unclear. Here we report for the first time the effects of short-term (250 ms) random noise electrical stimulation (RNS) on in-vitro acutely-isolated brain pyramidal neurons from the somatosensory and auditory cerebral cortex. We analyzed the correlation between the peak amplitude of the Na+ current and its latency for different levels of RNS. We found three groups of neurons. The first group exhibited a positive correlation, the second, a negative correlation, and the third group of neurons did not exhibit correlation. In the first group, both the peak amplitude of a TTX-sensitive Na+ current and its inverse of latency followed similar inverted U-like functions relative to the electrical RNS level. In this group, the RNS levels in which the maximal values of the inverted U-like functions occurred were the same. In the second group, the maximal values of the inverted U-like functions occurred at different levels. In the third group, only the peak amplitude of the Na+ current exhibited a clear inverted U-like function, but the inverse of the latency versus the electrical RNS, did not exhibit a clear inverted U-like function. A Hodgkin-Huxley neuron model reproduces our experimental results and shows that the observed behavior in the Na+ current could be due to the impact of RNS on the kinetics of activation and inactivation of the Na+ channels.

[Combination of noise plus weight-bearing accelerates consolidation time in tibial shaft fractures: A preliminary report]. / La combinación de ruido más carga de peso acelera la consolidación en las fracturas de la diáfisis tibial: Un informe preliminar.

Introduction: Long bones fractures are responsible for prolonged periods of incapacity and economic losses. New therapies for shortening the time of consolidation are needed. Thus, the purpose of this clinical study was to evaluate the efficacy of noise plus weight-bearing over the bone consolidation of tibial shaft fractures. Methods: In this clinical trial, 12 patients with tibial shaft fractures were recruited during a 24-month period. Participants were treated with intramedullary nails and randomized to two groups: an experimental group and a control group. Both groups underwent a rehabilitation program consisting of two daily walking sessions with progressive weight-bearing. Simultaneously, the experimental group received a noise stimulus on the fracture site with intensities of 0.1-0.6 N and frequencies of 0.1-50 Hz. Radiographic consolidation was evaluated by Radiographic Unión Scale of Tibia. Results: X-ray consolidation was achieved at 18.6 ± 3.6 weeks and 27.2 ± 6.9 weeks, for experimental and control group, respectively (p < 0.05). Recovery of mobility ranges in the knee and ankle was faster in the experimental group than in the control group. Conclusions: This new method to stimulate fracture consolidation has the following advantages: it is effective, portable, easy to use, and inexpensive.

Introducción: Las fracturas de huesos largos son causa de períodos prolongados de incapacidad y pérdidas económicas. Se necesitan nuevas terapias para acortar el tiempo de consolidación. Por lo tanto, el objetivo de este estudio clínico fue evaluar la eficacia del ruido más el soporte de peso sobre la consolidación ósea de las fracturas de la diáfisis tibial. Método: En este ensayo clínico, 12 pacientes con fracturas de la diáfisis tibial fueron reclutados durante un período de 24 meses. Los participantes fueron tratados con clavos intramedulares y luego aleatorizados a dos grupos: un grupo experimental y un grupo control. Ambos grupos se sometieron a un programa de rehabilitación que consta de dos sesiones diarias de caminata con soporte progresivo de peso. Simultáneamente, el grupo experimental recibió un estímulo de ruido en el sitio de la fractura con intensidades de 0.1-0.6 N y frecuencias de 0.1-50 Hz. La consolidación radiográfica se evaluó mediante la escala RUST. Resultados: La consolidación radiográfica se logró a las 18.6 ± 3.6 semanas en el grupo experimental y a las 27.2 ± 6.9 semanas en el grupo control (p < 0.05). La recuperación de los rangos de movilidad en la rodilla y el tobillo fue más rápida en el grupo experimental que en el grupo control. Conclusiones: Este nuevo método para estimular la consolidación de fracturas tiene las siguientes ventajas: es eficaz, portátil, fácil de usar y económico.

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

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.

Hippocampal-cerebellar involvement in enhancement of performance in word-based BRT with the presence of background noise: an initial fMRI study

Background noise may impose deleterious effects on cognitive processing. However, noise below the threshold level may increase the ability to detect stimuli via stochastic resonance mechanisms (SR). The present study investigates whether task performance is deteriorated or enhanced by 5-dB SNR and, if the task performance is enhanced, whether this facilitation in performance points to a particular neural area that serves to attenuate noise and/or increase effective task performance. The areas of interest are the cerebellum and hippocampus due to their roles in working memory (WM) and their links with attention. Fifteen healthy young Malay adults performed three tasks during fMRI scanning: listening to babble noise (N), WM task in quiet (WMQ), and WM task in noise (WMN). Activated regions during N are bilateral STG and MTG. Both WM tasks produced similar activation in a network of areas in the frontal, temporal and parietal lobes. However, the two tasks demonstrated marked differences in the left hippocampus, right posterior cerebellum, and bilateral anterior cerebellum. Moreover, the results obtained from the behavioral task demonstrated that participants responded better in the presence of noise. These results support the hypothesis that the left hippocampus, right posterior cerebellum, and bilateral anterior cerebellum may be involved in attenuating noise and/or increasing attention to task performance, which could be due to SR mechanisms operating in the presence of noise. These results collectively suggest leftward asymmetries during the tasks with the right posterior cerebellum, bilateral anterior cerebellum, and left hippocampus providing compensatory attention processes, at least in the context of this study.(AU)

Hippocampal-cerebellar involvement in enhancement of performance in word-based BRT with the presence of background noise: an initial fMRI study

Background noise may impose deleterious effects on cognitive processing. However, noise below the threshold level may increase the ability to detect stimuli via stochastic resonance mechanisms (SR). The present study investigates whether task performance is deteriorated or enhanced by 5-dB SNR and, if the task performance is enhanced, whether this facilitation in performance points to a particular neural area that serves to attenuate noise and/or increase effective task performance. The areas of interest are the cerebellum and hippocampus due to their roles in working memory (WM) and their links with attention. Fifteen healthy young Malay adults performed three tasks during fMRI scanning: listening to babble noise (N), WM task in quiet (WMQ), and WM task in noise (WMN). Activated regions during N are bilateral STG and MTG. Both WM tasks produced similar activation in a network of areas in the frontal, temporal and parietal lobes. However, the two tasks demonstrated marked differences in the left hippocampus, right posterior cerebellum, and bilateral anterior cerebellum. Moreover, the results obtained from the behavioral task demonstrated that participants responded better in the presence of noise. These results support the hypothesis that the left hippocampus, right posterior cerebellum, and bilateral anterior cerebellum may be involved in attenuating noise and/or increasing attention to task performance, which could be due to SR mechanisms operating in the presence of noise. These results collectively suggest leftward asymmetries during the tasks with the right posterior cerebellum, bilateral anterior cerebellum, and left hippocampus providing compensatory attention processes, at least in the context of this study.