Site Dependency of Anodal Transcranial Direct-Current Stimulation on Reaction Time and Transfer of Learning during a Sequential Visual Isometric Pinch Task.

Considering the advantages of brain stimulation techniques in detecting the role of different areas of the brain in human sensorimotor behaviors, we used anodal transcranial direct-current stimulation (a-tDCS) over three different brain sites of the frontoparietal cortex (FPC) in healthy participants to elucidate the role of these three brain areas of the FPC on reaction time (RT) during a sequential visual isometric pinch task (SVIPT). We also aimed to assess if the stimulation of these cortical sites affects the transfer of learning during SVIPT. A total of 48 right-handed healthy participants were randomly assigned to one of the four a-tDCS groups: (1) left primary motor cortex (M1), (2) left dorsolateral prefrontal cortex (DLPFC), (3) left posterior parietal cortex (PPC), and (4) sham. A-tDCS (0.3 mA, 20 min) was applied concurrently with the SVIPT, in which the participants precisely controlled their forces to reach seven different target forces from 10 to 40% of the maximum voluntary contraction (MVC) presented on a computer screen with the right dominant hand. Four test blocks were randomly performed at the baseline and 15 min after the intervention, including sequence and random blocks with either hand. Our results showed significant elongations in the ratio of RTs between the M1 and sham groups in the sequence blocks of both the right-trained and left-untrained hands. No significant differences were found between the DLPFC and sham groups and the PPC and sham groups in RT measurements within the SVIPT. Our findings suggest that RT improvement within implicit learning of an SVIPT is not mediated by single-session a-tDCS over M1, DLPFC, or PPC. Further research is needed to understand the optimal characteristics of tDCS and stimulation sites to modulate reaction time in a precision control task such as an SVIPT.

The Correlation between Neck Pain and Disability, Forward Head Posture, and Hyperkyphosis with Opium Smoking: A Cross-Sectional Study from Iran.

Opium smoking has been a common practice in Iran for many years, with people often smoking for long hours. During the COVID-19 pandemic, there was an increase in opium smoking due to false beliefs about its protective effects against COVID-19 infection. In this study, we aimed to examine the association between the non-ergonomic positions associated with traditional opium smoking in Iran and the development of neck pain and disability, forward head posture (FHP), and hyperkyphosis (HK). In this cross-sectional, correlational study, a total of 120 individuals who smoked opium were selected based on the inclusion criteria. They were interviewed about their addiction profile using the Lite version of the Addiction Severity Index and the Leeds Dependence Questionnaire. The presence of neck pain and disability was also evaluated using the Visual Analog Scale and the Neck Disability Index. The participants were examined for FHP via side-view photography and for HK using a flexible ruler. Data were analyzed using correlation coefficient tests and stepwise linear regression analysis. Based on the results, homelessness, the lifetime duration of opium smoking (in months), the duration of daily opium smoking (in minutes), and the severity of drug dependence had significant relationships with the severity of neck pain, neck disability, FHP, and HK. Homelessness was the strongest predictor of neck pain and disability (R2 = 0.367, p < 0.001), FHP (R2 = 0.457, p < 0.001), and HK (R2 = 0.476, p < 0.001), followed by the lifetime duration of opium smoking and the duration of daily opium smoking, respectively, in which R2 increased to 0.505 (p = 0.011), 0.546 (p = 0.022), and 0.570 (p = 0.004) with the addition of two other variables. Overall, an increase in the duration of sitting in non-ergonomic positions could lead to neck pain and disability, FHP, and HK due to the non-neutral posture of opium smokers.

The correlation between strength and range of motion of the neck muscles and opium smoking in Iran.

Objectives: Opium smoking is commonly practiced via traditional and novel routes in Iran. Both smoking methods are practiced in a non-ergonomic position. According to previous studies and our hypothesis, it can be potentially harmful to the cervical spine. Thus, the present study aimed to investigate the relationship between opium smoking and neck range of motion and neck muscle strength. Methods: In this cross-sectional and correlational study, the range of motion and strength of the neck muscles of 120 men with drug use disorder were measured by a CROM goniometer and a hand-held dynamometer. Other data gathering was performed using a demographic questionnaire, the Maudsley Addiction Profile, and the Persian version of Leeds Dependence Questionnaire. The obtained data were analyzed by Shapiro-Wilks test, Pearson's correlation coefficient and stepwise linear regression. Results: There was no significant correlation between the age of drug use onset and range of motion and muscle strength of the neck; however, the daily duration of opium smoking and the number of years of opium smoking were inversely and significantly correlated with the range of motion and muscle strength of the neck in some directions. Daily opium smoking time for decreasing in neck range of motion and total duration of opium smoking for reduction of neck muscles strength are stronger predictor variables. Conclusion: Opium smoking by traditional routes causes non-ergonomic positions and has a moderate significant correlation with reduced range of motion and neck muscle strength, in Iran. Highlights: - The harm of drug use disorder is not only AIDS and hepatitis, and harm reduction programs should go beyond the prevention of AIDS and hepatitis. According to more than 90% of smoking use of drug compared to other methods (oral and injectable, etc.) musculoskeletal disorders caused by the smoking use of drugs, have a greater cost burden in reducing the quality of life and the need for rehabilitation.- Drug abuse treatment and harm reduction programs should focus more seriously on replacing smoking use of drugs with oral medications assisted treatment.- Although in Iran and some countries in the region, a large number of people smoke opium for many years and sometimes all their lives, daily in a completely non-ergonomic position, but studying the deformation of the posture and musculoskeletal disorders related to the body position in them, is not a scientific concern and neither physical therapy researchers have paid attention to it nor addiction researchers.- Neck muscles strength and range of motion in opium addicts are correlated to the number of years of opium smoking and daily minutes of opium smoking, but not to its oral use.- There is no significant correlation between the onset age of continues and permanent opium smoking and substance dependence severity with neck range of motion and muscles strength.- People with drug use disorder (especially smoking users) as a large group of vulnerable people, should be the target population of musculoskeletal disorders researchers and addiction harm reduction researchers, and more experimental, comparative, cohort, etc. researches should be designed and implemented for them.

The effects of inter-trial interval on implicit learning of sequential visual isometric pinch task.

Sequential visual isometric pinch task (SVIPT) has been recently used as a visuomotor sequence task in clinical research. The influence of varying intervals between sequenced trials on the acquisition of implicit sequence learning is not yet determined for SVIPT. The aim of this study was to investigate the effects of inter-trial interval (ITI) on implicit motor sequence learning using SVIPT. A total of 32 healthy participants with mean age 31.3 ± 4.5 years participated in this study. Participants were randomly assigned to one of four ITI groups; (1, 2, 3 and 4 s). They were instructed to control their force on a force transducer to reach a number of targets which appeared on the computer screen by changing the pinch force exerted onto the transducer. In this study, outcome measures were movement time, error rate and skill, which were measured before and after training. Our results indicated that motor sequence learning similarly affected various ITIs. Indeed, all participants exhibited same improvement in implicit learning of SVIPT even though the ITIs varied from 1 to 4 s. Our findings suggest that implicit learning of SVIPT is independent of ITI within this range in healthy individuals.

Single-Session Anodal tDCS with Small-Size Stimulating Electrodes Over Frontoparietal Superficial Sites Does Not Affect Motor Sequence Learning.

Due to the potential of anodal transcranial direct current stimulation (a-tDCS) for enhancement of fine sequenced movements and increasing interest in achieving high level of fine movements in the trained and untrained hands especially at initial stage of learning, we designed this study to investigate whether the application of single-session a-tDCS with small-size stimulating electrodes over FPN sites, such as dorsolateral prefrontal cortex (DLPFC), primary motor cortex (M1) or posterior parietal cortex (PPC) could enhance sequence learning with the trained hand and these effects are transferred into the untrained hand or not. A total of 51 right-handed healthy participants were randomly assigned to one of the four stimulation groups: a-tDCS of left M1, DLPFC, PPC, or sham. Stimulation was applied for 20 min during a sequential visual isometric pinch task (SVIPT). Eight blocks of training using SVIPT were completed with the right hand during stimulation. Two blocks of sequence training with each hand were performed by participants as assessment blocks at three time points: baseline, 15 min and one day following the intervention. Behavioral outcomes including movement time, error rate and skill were assessed in all assessment blocks across three time points. We also measured corticospinal excitability, short-interval intracortical inhibition, and intracortical facilitation using single- and paired-pulse transcranial magnetic stimulation. The results indicated that the behavioral outcomes were significantly improved with the right trained hand, but this learning effect was not modulated by a-tDCS with small-size stimulating electrodes over the FPN. Transfer of learning into the untrained hand was observed in all four groups for movement time but not for the error rate or skill. Our results suggest that sequential learning in SVIPT and its transfer into the untrained hand were not sensitive to a single-session a-tDCS with small-size stimulating electrodes over left M1, DLPFC or PPC in young healthy participants.

Reliability of Motor Evoked Potentials Induced by Transcranial Magnetic Stimulation: The Effects of Initial Motor Evoked Potentials Removal.

INTRODUCTION: Transcranial magnetic stimulation (TMS) is a useful tool for assessment of corticospinal excitability (CSE) changes in both healthy individuals and patients with brain disorders. The usefulness of TMS-elicited motor evoked potentials (MEPs) for the assessment of CSE in a clinical context depends on their intra-and inter-session reliability. This study aimed to evaluate if removal of initial MEPs elicited by using two types of TMS techniques influences the reliability scores and whether this effect is different in blocks with variable number of MEPs. METHODS: Twenty-three healthy participants were recruited in this study. The stimulus intensity was set at 120% of resting motor threshold (RMT) for one group while the stimulus intensity was adjusted to record MEPs up to 1 mV for the other group. Twenty MEPs were recorded at 3 time points on 2 separate days. An intra-class correlation coefficient (ICC) reliability with absolute agreement and analysis of variance model were used to assess reliability of the MEP amplitudes for blocks with variable number of MEPs. RESULTS: A decrease in ICC values was observed with removal of 3 or 5 MEPs in both techniques when compared to all MEP responses in any given block. Therefore, removal of the first 3 or 5 MEPs failed to further increase the reliability of MEP responses. CONCLUSION: Our findings revealed that a greater number of trials involving averaged MEPs can influence TMS reliability more than removal of the first trials.

The effect of Kinesio taping technique on trigger points of the piriformis muscle.

BACKGROUND: Kinesio taping (KT) is a novel method which has recently emerged as a viable option to treat various musculoskeletal and neuromuscular deficits. The aim of this study was to determine the effects of KT on pain and hip joint range of motion (ROM) in individuals with myofacial trigger points in the piriformis muscle. METHODS: 51 patients with involvement of the piriformis muscle were assigned to experimental (N = 33) or control (N = 18) groups. The experimental group received KT with unloading techniques on the piriformis muscle and they were asked to keep this tape in place for three days. Pain and internal rotation (IR) of hip joints were measured at baseline, immediately after the KT application, and at a 72-h follow-up. RESULTS: The analysis of repeated measurement ANOVA yielded no main effects, but the interactions between group and time for each dependent variable (pain and ROM) were significant. A post-hoc analysis revealed significant improvement in pain and hip IR immediately postapplication and at a 72-h follow up in the KT group, while no significant change were found on dependent variables in the control group. DISCUSSION: Our findings suggests that KT application may be effective for pain relief and increasing ROM in patients with myofacial trigger points in the piriformis muscle.

The effect of anodal transcranial direct current stimulation on motor sequence learning in healthy individuals: A systematic review and meta-analysis.

A large number of studies have indicated the effect of anodal transcranial direct current stimulation (a-tDCS) on the primary motor cortex (M1) during motor skill training. The effects of a-tDCS on different stages of motor sequence learning are not yet completely understood. The purpose of this meta-analysis was to determine the effects of single and multiple sessions of a-tDCS on two different tasks: the sequential finger tapping task/serial reaction time task (SEQTAP/SRTT) and the sequential visual isometric pinch task (SVIPT). We searched electronic databases for M1 a-tDCS studies. Thirteen studies met the inclusion criteria. The results indicate that application of multiple sessions of a-tDCS, compared to single session a-tDCS induced a significant improvement in skill in both SEQTAP/SRTT and SVIPT. Retention after a single day and multiple days of a-tDCS was statistically significant for the SEQTAP/SRTT task but not for SVIPT. Therefore, our findings suggest that application of M1 a-tDCS across the three or five consecutive days can be helpful to improve motor sequence learning.

Validity and reliability of skin markers for measurement of intersegmental mobility at L2-3 and L3-4 during lateral bending in healthy individuals: a fluoroscopy study.

It is clinically important to assess kinematic parameters of lumbar spine movement to increase our understanding of lumbar mobility impairments in patients with low back pain. This is the first step for restoration of motor function. The use of non-invasive surface markers has currently attracted the interests of many researchers but scientific utilization of this technique for clinical research requires validity and reliability studies. The aim of the present study was to examine whether skin markers can be used to measure lumbar motions during lateral bending. Twelve healthy individuals were lying in prone position on the video fluoroscopy table and skin markers were attached over their spinous processes. Fluoroscopy images were taken in two positions of neutral and right lateral bending (RLB). The correlation of the L2-3 and L3-4 angles and lumbar curvature between markers and vertebrae measurements in the neutral and RLB positions was determined by Pearson Correlation Coefficient. The Intraclass correlation coefficient (ICC) was used to measure inter-examiner reliability of measurement in five participants. The results showed high reliability (ranging from 0.94 to 0.99) for angular measurements at L2-3 and L3-4 and lumbar curvature and also significant correlation between angular measurement derived from markers and vertebrae at L2-3 (r = 0.7, p = 0.015), L3-4 and lumbar curvature (r = 0.91 p = 0.001). The results showed that motions of skin markers follow the motions of the assigned underlying lumbar vertebrae. Therefore, skin markers can be confidently used for estimation of lumbar movements during lateral bending.

Effect of pain on the timing pattern of masseter muscle activity during the open-close-clench cycle in the migraine without aura and tension type headaches.

BACKGROUND: The existence of a pathophysiological link between headaches and muscle activity pattern is still being debated. The purpose of this study was to investigate the effect of pain on the timing pattern of the masseter muscle in patients with tension-type headache (TTH) and migraine without aura (MOA). METHODS: 57 women (22 controls, 19 MOA and 16 TTH) participated in the study. The electromyographic (EMG) activity of masseter during the open-close-clench cycle (OCC) was recorded in the interictal and ictal stages. RESULTS: In the interictal stage, the results showed no significant difference in EMG activity between patients and control groups. However, masseter muscles in subjects with TTH (both sides) and in MOA patients (left side) activated significantly earlier than the control in the ictal stage. The duration of left masseter was also significantly greater in the TTH than in the control group (P < 0.05). CONCLUSION: The findings of this study showed that activity pattern of masticatory muscles in headaches patients were affected by existence of pain. Furthermore, this study confirmed that temporal variables of EMG such as onset and duration rather than amplitude could be more reliable to identify altered activity pattern of muscles.