Cognitive, Mood, and Electroencephalographic Effects of Noninvasive Cortical Stimulation With Weak Electrical Currents

Objectives: The use of noninvasive cortical electrical stimulation with weak currents has significantly increased in basic and clinical human studies. Initial, preliminary studies with this technique have shown encouraging results; however, the safety and tolerability of this method of brain stimulation have not been sufficiently explored yet. The purpose of our study was to assess the effects of direct current (DC) and alternating current (AC) stimulation at different intensities in order to measure their effects on cognition, mood, and electroencephalogram. Methods: Eighty-two healthy, right-handed subjects received active and sham stimulation in a randomized order. We conducted 164 ninety-minute sessions of electrical stimulation in 4 different protocols to assess safety of (1) anodal DC of the dorsolateral prefrontal cortex (DLPFC); (2) cathodal DC of the DLPFC; (3) intermittent anodal DC of the DLPFC and; (4) AC on the zygomatic process. We used weak currents of 1 to 2 mA (for DC experiments) or 0.1 to 0.2 mA (for AC experiment). Results: We found no significant changes in electroencephalogram, cognition, mood, and pain between groups and a low prevalence of mild adverse effects (0.11% and 0.08% in the active and sham stimulation groups, respectively), mainly, sleepiness and mild headache that were equally distributed between groups. Conclusions: Here, we show no neurophysiological or behavioral signs that transcranial DC stimulation or AC stimulation with weak currents induce deleterious changes when comparing active and sham groups. This study provides therefore additional information for researchers and ethics committees, adding important results to the safety pool of studies assessing the effects of cortical stimulation using weak electrical currents. Further studies in patients with neuropsychiatric disorders are warranted.

Imperceptible electrical noise attenuates isometric plantar flexion force fluctuations with correlated reductions in postural sway

Optimal levels of noise stimulation have been shown to enhance the detection and transmission of neural signals thereby improving the performance of sensory and motor systems. The first series of experiments in the present study aimed to investigate whether subsensory electrical noise stimulation applied over the triceps surae (TS) in seated subjects decreases torque variability during a force-matching task of isometric plantar flexion and whether the same electrical noise stimulation decreases postural sway during quiet stance. Correlation tests were applied to investigate whether the noise-induced postural sway decrease is linearly predicted by the noise-induced torque variability decrease. A second series of experiments was conducted to investigate whether there are differences in torque variability between conditions in which the subsensory electrical noise is applied only to the TS, only to the tibialis anterior (TA) and to both TS and TA, during the force-matching task with seated subjects. Noise stimulation applied over the TS muscles caused a significant reduction in force variability during the maintained isometric force paradigm and also decreased postural oscillations during quiet stance. Moreover, there was a significant correlation between the reduction in force fluctuation and the decrease in postural sway with the electrical noise stimulation. This last result indicates that changes in plantar flexion force variability in response to a given subsensory random stimulation of the TS may provide an estimate of the variations in postural sway caused by the same subsensory stimulation of the TS. We suggest that the decreases in force variability and postural sway found here are due to stochastic resonance that causes an improved transmission of proprioceptive information. In the second series of experiments, the reduction in force variability found when noise was applied to the TA muscle alone did not reach statistical significance, suggesting that TS proprioception gives a better feedback to reduce force fluctuation in isometric plantar flexion conditions.

Comparison between the C5 or C6-Cz electrode assembly and C3 or C4-Cz assembly for transcranial electric motor activation of muscular response of the contralateral facial nerve

We used an assembly of electrodes C3 and C4-Cz in order to activate the motor cortical area of the corticobulbar tract to elucidate the motor-evoked potential of the contralateral mentalis muscle. We compared this setup to that of an assembly with electrodes C5 or C6-Cz using a train of electrical pulses and a single electrical pulse. This analysis was made in 23 consecutive patients who underwent several varied surgeries and were prospectively operated on at Santa Paula Hospital between January and June 2011. The results showed that the assembly with C5 or C6-Cz produced a multisynaptic motor-evoked potential in the contralateral mentalis muscle in 86.9 % of the patients, whereas 82.6 % of patients stimulated at points C3 or C4-Cz presented the same response. However, both assemblies showed similar behavior with the use of a single electrical pulse for peripheral contralateral nerve stimulation. We concluded that the C5 or C6-Cz assembly was similar to C3 or C4-Cz in obtaining a multisynaptic response in the contralateral mentalis muscle, although it required less intensive stimulation than the C3 or C4- Cz assembly.

Bat-Inspired Optimization Approach for the Brushless DC Wheel Motor Problem

This paper presents a metaheuristic algorithm inspired in evolutionary computation and swarm intelligence concepts and fundamentals of echolocation of micro bats. The aim is to optimize the mono and multiobjective optimization problems related to the brushless DC wheel motor problems, which has 5 design parameters and 6 constraints for the mono-objective problem and 2 objectives, 5 design parameters, and 5 constraints for multiobjective version. Furthermore, results are compared with other optimization approaches proposed in the recent literature, showing the feasibility of this newly introduced technique to high nonlinear problems in electromagnetics.

Motor cortex stimulation inhibits thalamic sensory neurons and enhances activity of PAG neurons: Possible pathways for antinociception

Motor cortex stimulation is generally suggested as a therapy for patients with chronic and refractory neuropathic pain. However, the mechanisms underlying its analgesic effects are still unknown. In a previous study, we demonstrated that cortical stimulation increases the nociceptive threshold of naive conscious rats with opioid participation. In the present study, we investigated the neurocircuitry involved during the antinociception induced by transdural stimulation of motor cortex in naive rats considering that little is known about the relation between motor cortex and analgesia. The neuronal activation patterns were evaluated in the thalamic nuclei and midbrain periaqueductal gray. Neuronal inactivation in response to motor cortex stimulation was detected in thalamic sites both in terms of immunolabeling (Zif268/Fos) and in the neuronal firing rates in ventral posterolateral nuclei and centromedian-parafascicular thalamic complex. This effect was particularly visible for neurons responsive to nociceptive peripheral stimulation. Furthermore, motor cortex stimulation enhanced neuronal firing rate and Fos immunoreactivity in the ipsilateral periaqueductal gray. We have also observed a decreased Zif268, delta-aminobutyric acid (GABA), and glutamic acid decarboxylase expression within the same region, suggesting an inhibition of GABAergic interneurons of the midbrain periaqueductal gray, consequently activating neurons responsible for the descending pain inhibitory control system. Taken together, the present findings suggest that inhibition of thalamic sensory neurons and disinhibition of the neurons in periaqueductal gray are at least in part responsible for the motor cortex stimulation-induced antinociception. (C) 2012 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

Speed Neuro-fuzzy Estimator Applied To Sensorless Induction Motor Control

This work proposes the development of an Adaptive Neuro-fuzzy Inference System (ANFIS) estimator applied to speed control in a three-phase induction motor sensorless drive. Usually, ANFIS is used to replace the traditional PI controller in induction motor drives. The evaluation of the estimation capability of the ANFIS in a sensorless drive is one of the contributions of this work. The ANFIS speed estimator is validated in a magnetizing flux oriented control scheme, consisting in one more contribution. As an open-loop estimator, it is applied to moderate performance drives and it is not the proposal of this work to solve the low and zero speed estimation problems. Simulations to evaluate the performance of the estimator considering the vector drive system were done from the Matlab/Simulink(R) software. To determine the benefits of the proposed model, a practical system was implemented using a voltage source inverter (VSI) to drive the motor and the vector control including the ANFIS estimator, which is carried out by the Real Time Toolbox from Matlab/Simulink(R) software and a data acquisition card from National Instruments.