Inhibition of motor cortex excitability with 15 Hz transcranial alternating current stimulation (tACS)

There remains a lack of solid evidence showing whether transcranial stimulation with weak alternating current (transcranial alternating current stimulation, tACS) can in fact induce significant neurophysiological effects. Previously, a study in which tACS was applied for 2 and 5 min with current density = 0.16-0.25 A/m(2) was unable to show robust effects on cortical excitability. Here we applied tACS at a significantly higher current density (0.80 A/m(2)) for a considerably longer duration (20 min) and were indeed able to demonstrate measurable changes to cortical excitability. Our results show that active 15 Hz tACS of the motor cortex (electrodes placed at C3 and C4) significantly diminished the amplitude of motor evoked potentials and decreased intracortical facilitation (ICF) as compared to baseline and sham stimulation. In addition, we show that our method of sham tACS is a reliable control condition. These results support the notion that AC stimulation with weak currents can induce significant changes in brain excitability; in this case, 15 Hz tACS led to a pattern of inhibition of cortical excitability. We propose that tACS may have a dampening effect on cortical networks and perhaps interfere with the temporal and spatial summation of weak subthreshold electric potentials. (C) 2010 Elsevier Ireland Ltd. All rights reserved.

Transcranial Electrocortical Stimulation to Monitor the Facial Nerve Motor Function During Cerebellopontine Angle Surgery

OBJECTIVE: This study was conducted to investigate the success rate of using the facial motor evoked potential (FMEP) of orbicularis oculi and oris muscles for facial nerve function monitoring with use of a stepwise protocol, and its usefulness in predicting facial nerve outcome during cerebellopontine angle (CPA) surgeries. METHODS: FMEPs were recorded intraoperatively from 60 patients undergoing CPA surgeries. Transcranial electrocortical stimulation (TES) was performed using corkscrew electrodes positioned at hemispheric montage (C3/C4 and CZ). The contralateral abductor pollicis brevis muscle was used as the control response. Stimulation was always applied contralaterally to the affected side using 1, 3, or 5 rectangular pulses ranging from 200 to 600 V with 50 mu s of pulse duration and an interstimulus interval of 2 ms. Facial potentials were recorded from needles placed in the orbicularis oculi and oris muscles. RESULTS: FMEP from the orbicularis oris and oculi muscles could be reliably monitored in 86.7% and 85% of the patients, respectively. The immediate postoperative facial function correlated significantly with the FMEP ratio in the orbicularis oculi muscle at 80% amplitude ratio (P =.037) and orbicularis oris muscle at 35% ratio (P =.000). FMEP loss was always related to postoperative facial paresis, although in different degrees. CONCLUSION: FMEPs can be obtained reliably by using TES with 3 to 5 train pulses. Stable intraoperative FMEPs can predict a good postoperative outcome of facial function. However, further refinements of this technique are necessary to minimize artifacts and to make this method more reliable.

Gamma band oscillations under influence of bromazepam during a sensorimotor integration task: An EEG coherence study

The goal of the present study was to explore the dynamics of the gamma band using the coherence of the quantitative electroencephalography (qEEG) in a sensorimotor integration task and the influence of the neuromodulator bromazepam on the band behavior. Our hypothesis is that the needs of the typewriting task will demand the coupling of different brain areas, and that the gamma band will promote the binding of information. It is also expected that the neuromodulator will modify this coupling. The sample was composed of 39 healthy subjects. We used a randomized double-blind design and divided subjects into three groups: placebo (n = 13), bromazepam 3 mg (n = 13) and bromazepam 6 mg (n = 13). The two-way ANOVA analysis demonstrated a main effect for the factors condition (i.e., C4-CZ electrode pair) and moment (i.e., C3-CZ, C3-C4 and C4-CZ pairs of electrodes). We propose that the gamma band plays an important role in the binding among several brain areas in complex motor tasks and that each hemisphere is influenced in a different manner by the neuromodulator. (C) 2009 Elsevier Ireland Ltd. All rights reserved.

Effects of bromazepam in frontal theta activity on the performance of a sensorimotor integration task: A quantitative electroencephalography study

Our objective is to verify the modulatory effects of bromazepam on EEG theta absolute power when subjects were submitted to a visuomotor task (i.e., car driver task). Sample was composed of 14 students (9 males and 5 females), right handed, with ages varying between 23 and 42 years (mean = 32.5 +/- 9.5), absence of mental or physical impairments, no psychoactive or psychotropic substance use and no neuromuscular disorders (screened by a clinical examination). The results showed an interaction between condition and electrodes (p=0.034) in favor of F8 electrode compared with F7 in both experimental conditions (t-test; p=0.001). Additionally, main effects were observed for condition (p=0.001), period (p=0.001) and electrodes (p=0.031) in favor of F4 electrode compared with F3. In conclusion, Br 6 mg of bromazepam may interfere in sensorimotor processes in the task performance in an unpredictable scenario allowing that certain visuospatial factors were predominant. Therefore, the results may reflect that bromazepam effects influence the performance of the involved areas because of the acquisition and integration of sensory stimuli processes until the development of a motor behavior based on the same stimuli. (C) 2009 Elsevier Ireland Ltd. All rights reserved.

The effects of bromazepam over the temporo-parietal areas during the performance of a visuomotor task: A qEEG study

This study investigated the effects of bromazepam on qEEG when 14 healthy subjects were asked to perform a visuomotor task (i.e., motor vehicle driving task). The subjects were exposed to two experimental conditions: the placebo (PL) and 6 mg of bromazepam (Br 6 mg), following a randomized, double-blind design on different days. Specifically, we observe absolute power extracted from qEEG data for theta band. We expected to see a decrease in absolute theta power in the temporal and parietal areas due to the influence of bromazepam for the experimental group when compared with the placebo group. We found a main effect for the condition factor for electrodes T3, T4, P3 and P4. We also observed a main effect for the period factor for electrodes P3 and P4. We observed that the ingestion of 6 mg of bromazepam induces different patterns in theta power at the temporal and parietal sites. We concluded that 6 mg of bromazepam was an important factor in the fluctuation of the activities in the temporal and parietal areas. We then hypothesize about the specific role of this drug during the execution of a visuomotor task and within the sensorimotor integration process. (C) 2011 Elsevier Ireland Ltd. All rights reserved.

The role played by the parietoocciptal cortex in the process of sensory-motor integration: An electroencephalographic study

Introduction. A fundamental aspect of planning future actions is the performance and control of motor tasks. This behaviour is done through sensory-motor integration. Aim. To explain the electrophysiological mechanisms in the cortex (modifications to the alpha band) that are involved in anticipatory actions when individuals have to catch a free-falling object. Subjects and methods. The sample was made up of 20 healthy subjects of both sexes (11 males and 9 females) with ages ranging between 25 and 40 years (32.5 +/- 7.5) who were free of mental or physical diseases (previous medical history); the subjects were right-handed (Edinburgh Inventory) and were not taking any psychoactive or psychotropic substances at the time of the study. The experiment consisted in a task in which subjects had to catch freely falling objects. The experiment was made up of six blocks of 15 tests, each of which lasted 2 minutes and 30 seconds before and two seconds after each ball was dropped. Results. An interaction of the factors moment and position was only observed for the right parietooccipital cortex, in the combination of electrodes P4-O2. Conclusion. These findings suggest that the right parietooccipital cortex plays an important role in increasing expectation and swiftness in the process of preparing for a motor task.

High and Low Frequency TENS Reduce Postoperative Pain Intensity After Laparoscopic Tubal Ligation A Randomized Controlled Trial

Background: Transcutaneous electrical nerve stimulation (TENS) is an effective adjunctive therapy for postoperative pain; however, effects of different frequencies Of stimulation have not been systematically investigated. Laparoscopic sterilization (LS) causes significant pain in the early postoperative period and requires substantial postoperative medication. Therefore, we studied the effects of TENS on postoperative pain after LS through placement of Yoon fallopian rings in a prospective, randomized, double-blinded, and placebo-controlled study. Methods: Sixty-four patients undergoing LS for uterine tube ligation were randomly allocated to receive either active TENS or placebo TENS. Postoperative pain was evaluated using a standard I I-point numeric rating scale and the McGill Pain Questionnaire (MPQ)-pain rating index and number of words chosen. Both high frequency (100 Hz) and low frequency (4 Hz) TENS, at strong, but comfortable sensory intensity, were applied for 20 minutes through 4 electrodes placed around the surgical incision immediately after Surgery. Pain was assessed before and after application of TENS when patients were at postanesthesia care unit (PACU). Results: Both high and low frequency TENS significantly decreased postoperative pain intensity when compared with before administration of TENS using the numeric rating scale (P = 0.001), pain rating index (P = 0.001), and number of words chosen (P 0.001) compared with placebo TENS (P = 0.001). TENS in combination with standard pharmacologic analgesic treatment was efficacious for postoperative pain relief after LS. Conclusions: We recommend regular use of multimodal therapy with TENS and analgesic drugs after LS with placement of Yoon rings.

Activation of the shoulder and arm muscles during axial load exercises on a stable base of support and on a medicine ball

The purpose of this study was to compare SEMG activities during axial load exercises on a stable base of support and on a medicine ball (relatively unstable). Twelve healthy male volunteers were tested (x = 23 +/- 7y). Surface EMG was recorded from the biceps brachii, anterior deltoid, clavicular portion of pectoralis major, upper trapezius and serratus anterior using surface differential electrodes. All SEMG data are reported as percentage of RMS mean values obtained in maximal voluntary contractions for each muscle studied. A 3-way within factor repeated measures analysis of variance was performed to compare RMS normalized values. The RMS normalized values of the deltoid were always greater during the exercises performed on a medicine ball in relation to those performed on a stable base of support. The trapezius showed greater mean electric activation amplitude values on the wall-press exercise on a medicine ball, and the pectoralis major on the push-up. The serratus and biceps did not show significant differences of electric activation amplitude in relation to both tested bases of support. Independent of the base of support, none of the studied muscles showed significant differences of electric activation amplitude during the bench-press exercise. The results contribute to the identification of the levels of muscular activation amplitude during exercises that are common in clinical practice of rehabilitation of the shoulder and the differences in terms of type of base of support used. (C) 2006 Elsevier Ltd. All rights reserved.

ELECTROMYOGRAPHIC AMPLITUDE RATIO OF SERRATUS ANTERIOR AND UPPER TRAPEZIUS MUSCLES DURING MODIFIED PUSH-UPS AND BENCH PRESS EXERCISES

Imbalance and weakness of the serratus anterior and upper trapezius force couple have been described in patients with shoulder dysfunction. There is interest in identifying exercises that selectively activate these muscles and including it in rehabilitation protocols. This study aims to verify the UT/SA electromyographic (EMG) amplitude ratio, performed in different upper limb exercises and on two bases of support. Twelve healthy men were tested (average age = 22.8 +/- 3.1 years), and surface EMG was recorded from the upper trapezius and serratus anterior using single differential surface electrodes. Volunteers performed isometric contractions over a stable base of support and on a Swiss ball during the wall push-up (WP), bench press (BP), and push-up (PU) exercises. All SEMG data are reported as a percentage of root mean square or integral of linear envelope from the maximal value obtained in one of three maximal voluntary contractions for each muscle studied. A linear mixed-effect model was performed to compare UT/SA ratio values. The WP, BP, and PU exercises showed UT/SA ratio mean +/- SD values of 0.69 +/- 0.72, 0.14 +/- 0.12, and 0.39 +/- 0.37 for stable surfaces, respectively, whereas for unstable surfaces, the values were 0.73 +/- 0.67, 0.43 +/- 0.39, and 0.32 +/- 0.30. The results demonstrate that UT/SA ratio was influenced by the exercises and by the upper limb base of support. The practical application is to show that BP on a stable surface is the exercise preferred over WP and PU on either surfaces for serratus anterior muscle training in patients with imbalance between the UT/SA force couple or serratus anterior weakness.

Evaluation of swallowing in children with vomiting after feeding

Vomiting after feeding is a symptom of gastroesophageal reflux (GER) and of eosinophilic esophagitis (EE), which are considered to be a cause of infant feeding disorder. The objective of the present study was to evaluate swallowing in children with feeding disorder manifested by vomiting after feeding. Using clinical and videofluoroscopic methods we studied the swallowing of 37 children with vomiting after feeding (mean age = 15.4 months), and of 15 healthy children (mean age = 20.5 months). In the videofluoroscopic examination the children swallowed a free volume of milk and 5 ml of mashed banana, both mixed with barium sulfate. We evaluated five swallows of liquid and five swallows of paste. The videofluoroscopic examination was recorded at 60 frames/s. Patients had difficulty during feeding, pneumonia, respiratory distress, otitis, and irritability more frequently than controls. During feeding, children with vomiting, choke were irritable, and refused food more frequently than controls, and during the videofluoroscopic examination the patients had more backward movement of the head than controls for both the liquid and paste boluses. There was no difference in the timing of oral swallowing transit, pharyngeal swallowing transit, or pharyngeal clearance between patients and controls. We conclude that children with vomiting after feeding may have difficulties in accepting feeding, although they have no alteration of oral and pharyngeal phases of swallowing.

A new DTL-electrode holder for recording of electroretinograms in animals

Purpose: Contact lens electrodes (CLEs) are frequently used to register electroretinograms (ERGs) in small animals such as mice or rats. CLEs are expensive to buy or difficult to be produced individually. In addition, CLE`s have been noticed to elicit inconstant results and they carry potential to injure the cornea. Therefore, a new electrode holder was constructed based on the clinically used DTL-electrode and compared to CLEs. Material and methods: ERGs were recorded with both electrode types in nine healthy Brown-Norway rats under scotopic conditions. For low intensity responses a Naka-Rushton function was fitted and the parameters V(max), k and n were analyzed. The a-wave, b-wave and oscillatory potentials were analyzed for brighter flash intensities (1-60 scot cd s/m(2)). Repeatability was assessed for both electrode types in consecutive measurements. Results: The new electrode holder was faster in setting up than the CLE and showed lower standard deviations. No corneal alterations were observed. Slightly higher amplitudes were recorded in most of the measurements with the new electrode holder (except amplitudes induced by 60 cd s/m(2)). A Bland-Altman test showed good agreement between the DTL holder and the CLE (mean difference 35.2 mu V (Holder-CLE)). Pearson`s correlation coefficient for test-retest-reliability was r = 0.783. Conclusions: The DTL holder was superior in handling and caused far less corneal problems than the CLE and produced comparable or better electrophysiological results. The minimal production costs and the possibility of adapting the DTL holder to bigger eyes, such as for dogs or rabbits, offers with broader application prospects. (C) 2010 Elsevier B.V. All rights reserved.

Transcorneal Electrical Stimulation for Patients with Retinitis Pigmentosa: A Prospective, Randomized, Sham-Controlled Exploratory Study

PURPOSE. To assess the safety of transcorneal electrical stimulation (TES) and explore its efficacy in various subjective and objective parameters of visual function in patients with retinitis pigmentosa (RP). METHODS. Twenty-four patients in this prospective, randomized, partially blinded, good-clinical-practice study underwent TES (5-ms biphasic pulses; 20 Hz; DTL electrodes) 30 minutes per week for 6 consecutive weeks. The patients were randomly assigned to one of three groups: sham, 66%, or 150% of individual electrical phosphene threshold (EPT). Visual acuity (VA), visual field (VF; kinetic, static), electroretinography (Ganzfeld, multifocal), dark-adaptation (DA), color discrimination, and EPTs were assessed at all visits or four times, according to the study plan. RESULTS. TES using DTL electrodes was tolerated well; all patients finished the study. Two adverse (foreign body sensation), but no serious adverse events were encountered. There was a tendency for most functional parameters to improve (8/18) or to remain constant (8/18) in the 150% group. VF area and scotopic b-wave amplitude reached statistical significance (P < 0.027 and P < 0.001, respectively). Only desaturated color discrimination and VF mean sensitivity decreased. There was no obvious trend in the 66% group. CONCLUSIONS. TES was found to be safe in RP patients. Positive trends were discovered, but due to the small sample size of this exploratory study, statistical significance was reached only for VF area and scotopic b-wave amplitude. Further studies with larger sample sizes and longer duration are needed to confirm the findings and to define optimal stimulation parameters. (ClinicalTrials.gov number, NCT00804102.) (Invest Ophthalmol Vis Sci. 2011;52:4485-4496) DOI:10.1167/iovs.10-6932

The ACB technique: a biomagentic tool for monitoring gastrointestinal contraction directly from smooth muscle in dogs

The aim of this paper was to verify whether AC biosusceptometry (ACB) is suitable for monitoring gastrointestinal (GI) contraction directly from smooth muscle in dogs, comparing with electrical recordings simultaneously. All experiments were performed in dogs with magnetic markers implanted under the serosa of the right colon and distal stomach, and their movements were recorded by ACB. Monopolar electrodes were implanted close to the magnetic markers and their electric potentials were recorded by electromyography (EMG). The effects of neostigmine, hyoscine butylbromide and meal on gastric and colonic parameters were studied. The ACB signal from the distal stomach was very similar to EMG; in the colonic recordings, however, within the same low-frequency band, ACB and EMG signals were characterized by simultaneity or a widely changeable frequency profile with time. ACB recordings were capable of demonstrating the changes in gastric and colonic motility determined by pharmacological interventions as well as by feeding. Our results reinforce the importance of evaluating the mechanical and electrical components of motility and show a temporal association between them. ACB and EMG arecomplementary for studying motility, with special emphasis on the colon. ACB offers an accurate method for monitoring in vivo GI motility.

Effect of Gender on Swallow Event Duration Assessed by Videofluoroscopy

There are data suggesting that women swallow liquids at a lower flow rate and ingest smaller volumes in each swallow than men. Our objective in this work was to compare swallowing in asymptomatic men and women by videofluoroscopy. We studied 18 men [age = 33-77 years, mean = 61 (10) years] and 12 women [age = 29-72 years, mean = 53 (15) years] who swallowed in duplicate 5 and 10 ml of liquid and paste barium boluses. None of the volunteers had dysphagia, neurologic diseases, or oral, pharyngeal, or esophageal diseases. The videofluoroscopic examination showed that for the 5-ml bolus, women had a longer oropharyngeal transit [liquid: men, 0.63 (0.21) s, women, 0.88 (0.39) s; paste: men, 0.64 (0.35) s, women, 0.94 (0.58) s], longer oral transit [liquid: men, 0.41 (0.21) s, women, 0.59 (0.35) s; paste: men, 0.39 (0.28) s, women, 0.59 (0.42) s], and longer pharyngeal clearance [liquid: men, 0.36 (0.11) s, women, 0.45 (0.16) s; paste: men, 0.42 (0.25) s, women, 0.56 (0.27) s] compared with men (p < 0.05). We conclude that there are differences in swallowing between men and women, with women having a longer oropharyngeal transit than men for a 5-ml bolus.

Hypoalgesic effect of the transcutaneous electrical nerve stimulation following inguinal herniorrhaphy: A randomized, controlled trial

We investigated the effect of transcutaneous electrical nerve stimulation (TENS) for inguinal herniorrhaphy postoperative pain control in a prospective, randomized, double-blinded, placebo-controlled study. Forty patients undergoing unilateral inguinal herniorrhaphy with an epidural anesthetic technique were randomly allocated to receive either active TENS or placebo TENS. Postoperative pain was evaluated using a standard 10-point numeric rating scale (NRS). Analgesic requirements were also recorded. TENS (100 Hz, strong but comfortable sensory intensity) was applied for 30 minutes through 4 electrodes placed around the incision twice, 2 and 4 hours after surgery. Pain was assessed before and after each application of TENS and 8 and 24 hours after surgery. In the group treated with active TENS, pain intensity was significantly lower 2 hours (P = .028), 4 hours (P = .022), 8 hours (P = .006), and 24 hours (P = .001) after the surgery when compared with the group that received placebo TENS. Active TENS also decreased analgesic requirements in the postoperative period when compared with placebo TENS (P = .001). TENS is thus beneficial for postoperative pain relief, after inguinal herniorrhaphy; it has no observable side effects, and the pain-reducing effect continued for at least 24 hours. Consequently, the routine use of TENS after inguinal herniorrhaphy is recommended. Perspective: This study presents the hypoalgesic effect of high-frequency TENS for postoperative pain after inguinal herniorrhaphy. This may reinforce findings from basic science showing an opioid-like effect provided by TENS, given that high-frequency TENS has been shown to activate delta-opioid receptors. (C) 2008 by the American Pain Society.