Weighted Coherence Analysis as a Window into the Neurophysiological Effects of Traumatic Brain Injury.

Traumatic brain injury (TBI), resulting from external forces, is a leading cause of disability and death, often leading to cognitive deficits that affect attention, concentration, speech and language, learning and memory, reasoning, planning, and problem-solving. Given the diverse mechanisms underlying TBI symptoms, it is essential to characterize its neurophysiological and neuropsychological effects. To address this, we employed weighted coherence (WC) analysis in patients performing the Halstead-Reitan categorization task, alongside a control group of eight healthy individuals.

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 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.

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.

The Hemodynamic Mass Action of a Central Pattern Generator.

The hemodynamic response is a neurovascular and metabolic process in which there is rapid delivery of blood flow to a neuronal tissue in response to neuronal activation. The functional magnetic resonance imaging (fMRI) and the functional near-infrared spectroscopy (fNIRS), for instance, are based on the physiological principles of such hemodynamic responses. Both techniques allow the mapping of active neuronal regions in which the neurovascular and metabolic events are occurring.

Afterdischarges of Spinal Interneurons Following a Brief High-Frequency Stimulation of Ia Afferents in the Cat.

Spinal motoneurons exhibit sustained afterdischarges and plateau potentials following a brief high-frequency stimulation of Ia afferents. Also, there is evidence that spinal cord interneurons exhibit plateau potentials. However, to our knowledge, there are no reports about the possible afterdischarge behavior of lumbar spinal interneurons activated by Ia afferents.

Resetting the Respiratory Rhythm with a Spinal Central Pattern Generator.

There is evidence that a variety of central and afferent stimuli, including swallowing, can produce phase resetting in the respiratory rhythmicity. Also, there are reports about the intrinsic linkage between locomotion and respiration. However, little is known about the interaction between the central pattern generators (CPGs) for scratching and respiration.

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.

Augmenting EEG-global-coherence with auditory and visual noise: Multisensory internal stochastic resonance.

The present investigation documents the electrophysiological occurrence of multisensory internal stochastic resonance (MISR) in the human electroencephalographic (EEG) coherence elicited by auditory and visual noise.We define MISR of EEG coherence as the phenomenon for which an intermediate level of input noise of a sensory modality enhances EEG coherence in response to another noisy sensory modality. Here, EEG coherence is computed by the global weighted coherence (GWC), modulated by quasi-Brownian noise.

The Spinal Neurons Exhibit an ON-OFF and OFF-ON Firing Activity Around the Onset of Fictive Scratching Episodes in the Cat.

In a previous report, we found neurons with ON-OFF and OFF-ON firing activity in the obex reticular formation during scratching. The aim of the present study was to examine whether the spinal neurons also exhibit this type of activity in relation to the "postural stage" of fictive scratching in the cat. We found that the extensor and intermediate scratching neurons exhibit an ON-OFF firing rate; conversely, the flexor neurons show an OFF-ON activity, relative to every scratching episode.

The Complexity of H-wave Amplitude Fluctuations and Their Bilateral Cross-Covariance Are Modified According to the Previous Fitness History of Young Subjects under Track Training.

The Hoffmann reflex (H-wave) is produced by alpha-motoneuron activation in the spinal cord. A feature of this electromyography response is that it exhibits fluctuations in amplitude even during repetitive stimulation with the same intensity of current. We herein explore the hypothesis that physical training induces plastic changes in the motor system.

Optogenetic noise-photostimulation on the brain increases somatosensory spike firing responses.

We examined whether the optogenetic noise-photostimulation (ONP) of the barrel cortex (BC) of anesthetized Thy1-ChR2-YFP transgenic mice increases the neuronal multiunit-activity response evoked by whisker mechanical stimulation (whisker-evoked MUA). In all transgenic mice, we found that the signal-to-noise ratio (SNR) of such whisker-evoked MUA signals exhibited an inverted U-like shape as a function of the ONP level. Numerical simulations of a ChR2-expressing neuron model qualitatively support our experimental data.

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).

Stochastic resonance in the synaptic transmission between hair cells and vestibular primary afferents in development.

The stochastic resonance (SR) is a phenomenon of nonlinear systems in which the addition of an intermediate level of noise improves the response of such system. Although SR has been studied in isolated hair cells and in the bullfrog sacculus, the occurrence of this phenomenon in the vestibular system in development is unknown. The purpose of the present study was to explore for the existence of SR via natural mechanical-stimulation in the hair cell-vestibular primary afferent transmission.

Effect of mechanical tactile noise on amplitude of visual evoked potentials: multisensory stochastic resonance.

The present investigation documents the electrophysiological occurrence of multisensory stochastic resonance in the human visual pathway elicited by tactile noise. We define multisensory stochastic resonance of brain evoked potentials as the phenomenon in which an intermediate level of input noise of one sensory modality enhances the brain evoked response of another sensory modality. Here we examined this phenomenon in visual evoked potentials (VEPs) modulated by the addition of tactile noise.

Transition of pattern generation: the phenomenon of post-scratching locomotion.

A fundamental problem in neurophysiology is the understanding of neuronal mechanisms by which the central nervous system produces a sequence of voluntary or involuntary motor acts from a diverse repertory of movements. These kinds of transitions between motor acts are extremely complex; however, they could be analyzed in a more simple form in decerebrate animals in the context of spinal central pattern generation. Here, we present for the first time a physiological phenomenon of post-scratching locomotion in which decerebrate cats exhibit a compulsory locomotor activity after an episode of scratching.