Transcranial direct current stimulation over the primary motor cortex improves speech production in post-stroke dysarthric speakers: A randomized pilot study.

PURPOSE: The current study investigated the therapeutic potential of transcranial direct current stimulation (tDCS) on speech intelligibility, speech-related physiological and vocal functions among post-stroke dysarthric patients. METHOD: Nine chronic post-stroke dysarthric patients were randomly assigned to the stimulation or sham group. The stimulation group received 2mA of anodal tDCS over the left inferior primary motor cortex for 15 minutes, while the sham group received 30s of stimulation under the same settings. All the participants received 10 daily 15 minutes of individualized speech therapy targeting their dominant phonological process or phonemes with the greatest difficulty. The outcome measures included (1) perceptual analysis of single words, passage reading and diadochokinetic rate, (2) acoustic analysis of a sustained vowel, and (3) kinematic analysis of rapid syllable repetitions and syllable production in sentence, conducted before and after the treatment. RESULTS: The results revealed that both the stimulation and sham groups had improved perceptual speech intelligibility at the word level, reduced short rushes of speech during passage reading, improved rate during alternating motion rate, AMR-kha1, and improved articulatory kinematics in AMR-tha1 and syllables /tha1/ and /kha1/ production in sentence. Compared to the sham group, the stimulation group showed significant improvement in articulatory kinematics in AMR-kha1 and syllable /kha1/ production in sentence. The findings also showed that anodal stimulation led to reduced shimmer value in sustained vowel /a/ phonation, positive changes in articulatory kinematics in AMR-tha1 and syllables /pha1/ and /kha1/ production in sentence at the post treatment measure. In addition to positive effects on articulatory control, reduced perturbation of voice amplitude documented in the stimulation group post treatment suggests possible tDCS effects on the vocal function. CONCLUSIONS: The current study documented the beneficial effects of anodal tDCS over the primary motor cortex on speech production and suggested that combined tDCS and speech therapy may promote recovery from post-stroke dysarthria.

Effect of dry-electrode-based transcranial direct current stimulation on chronic low back pain and low back muscle activities: A double-blind sham-controlled study.

BACKGROUND: Dry-electrode-based transcranial direct current stimulation is a new type of non-invasive brain stimulation system which relieves chronic low back pain and improves related muscle movement, in a way that overcomes the drawback of conventional systems. OBJECTIVE: To investigate the effectiveness of dry-electrode-based transcranial direct current stimulation in relieving chronic low back pain and altering pain-related low back muscles movement, by using pain assessment tool and surface electromyographic topography. METHODS: We conducted a prospective, double-blind, randomized, sham-controlled study. 60 patients with non-specific chronic low back pain were randomly and evenly allocated into tDCS and sham groups. Each group accepted a single 20-minute stimulation at 2 mA on the primary motor cortex. Numeric rating scale for pain intensity assessment and root-mean-square difference parameter from surface electromyographic topography were measured before and after stimulation. The current direction in brain using finite element method was simulated to verify the current distribution under dry stimulation electrode. RESULTS: After stimulation, the pain intensity in the tDCS group significantly decreased, while it did not show evident change in the sham group. However, change of root-mean-square difference parameters between tDCS and sham groups showed no significant difference. Simulation results based on finite element method showed most of current focused on primary motor cortex while peak value of current density was 0.225 A/m2. CONCLUSIONS: Dry-electrode-based transcranial direct current stimulation can lower pain perception in patients with chronic low back pain. The analgesic mechanism can affect the top-down modulation pathway of pain.

Investigating Changes in Real-time Conscious Postural Processing by Older Adults during Different Stance Positions Using Electroencephalography Coherence.

Background/Study Context: Adjustments of posture in response to balance challenges may lead to subsequent increases in conscious posture processing. If cognitive resources are stretched by conscious processing of postural responses fewer resources will be available to attend to environmental trip or fall hazards. The objective of the study was to explore brain activity related to conscious processing of posture as a function of movement specific reinvestment and fear of falling. Method: Forty-three older adults (M = 71.4, SD = 4.1) stood with a wide or narrow stance on a force-plate while neural coherence between verbal-analytical (T3) and motor planning (Fz) regions of the brain was assessed using electroencephalography. The propensity for movement specific reinvestment was assessed using the Chinese version Movement Specific Reinvestment Scale (MSRS-C) and fear of falling was assessed using the Chinese version Fall Efficacy Scale International (FES-I[CH]). Results: Scores from the MSRS-C were negatively correlated with changes in T3-Fz coherence that occurred when participants shifted from wide to narrow stance. Together, MSRS-C and FES-I(CH) uniquely predicted the percentage change in T3-Fz coherence between the two stance conditions. Conclusion: Presented with two postural tasks of different complexities, participants with a lower propensity for conscious control of their movements (movement specific reinvestment) exhibited larger changes in real-time brain activity (neural coherence) associated with conscious postural processing.

Effects of transcranial direct current stimulation over the Broca's area on tongue twister production.

PURPOSE: The present study aimed to explore the short-term effect of anodal transcranial direct current stimulation (tDCS) on tongue twister production. METHOD: Thirty healthy native Cantonese adult speakers were randomly assigned to the anodal tDCS group or the sham tDCS group. Anodal tDCS of 2 mA was applied over the Broca's area of the brain. The stimulation lasted for 20 min for the anodal tDCS group and 30 s for the sham tDCS group. The participants were instructed to produce a list of tongue twisters before, immediately after and 4 h after tDCS. RESULT: Speech rate and response accuracy measured immediately after stimulation were significantly faster and higher, respectively, than before stimulation. Although there was no change in speech rate measured at 4 h after stimulation, response accuracy at that time point was significantly lower than that measured immediately after stimulation. However, there were no significant differences between the anodal tDCS and sham tDCS groups in either speech rate or response accuracy. CONCLUSION: The findings revealed that a single session of anodal tDCS over the Broca's area did not significantly improve speech production during tongue twister production.

Transcranial direct current stimulation of the primary motor cortex on postoperative pain and spontaneous oscillatory electroencephalographic activity following lumbar spine surgery: A pilot study.

BACKGROUND: Transcranial direct current stimulation (tDCS) on primary motor cortex (M1) provides a new way to relieve postoperative pain. Previous studies only found postoperative analgesia dosage significantly reduced in tDCS group while the patient-controlled analgesia (PCA) was applied. However, there lacks the study about the effect of M1-tDCS on pain intensity and brain activity while the analgesia dosage is the same for both groups. OBJECTIVE: To investigate whether M1-tDCS can (1) reduce pain intensity and (2) change spontaneous electroencephalography (EEG) oscillations in prefrontal cortex, in patients with postoperative pain, after taking the constant dosage of analgesics. METHODS: A prospective, single-blind, randomized, sham-controlled study was conducted. 32 patients with postoperative pain after lumbar spine surgery were recruited. All patients received same dosage of dezocine before intervention. In the morning of the first day after surgery and before dezocine injection, a single 20-minute session of anodal M1-tDCS was applied to 'tDCS' group while sham stimulation to 'sham' group. Numeric rating scale (NRS) and resting-state EEG with eyes-closed were measured and analyzed. EEG spectral powers were analyzed using repeated measures analysis of variance (ANOVA). Correlation analysis was conducted between the change of NRS and the change of spectral power. RESULTS: The NRS in "tDCS" group significantly decreased (p < 0.01) while not in "sham" group after intervention. Only spectral power within alpha2 band (10-13 Hz) in Fp1 and beta1 band (13-20 Hz) in Fp1 showed significant Time×Intervention interaction effect. These changes of the spectral power also showed significant correlation with the change of NRS. CONCLUSIONS: The postoperative pain intensity in patients receiving surgery could reduce after a single session of anodal M1-tDCS compared to sham M1-tDCS. The effect to the top-down dimension of postoperative pain might account for the analgesic effect of M1-tDCS, which reflecting slow oscillations in left prefrontal EEG.

Multitask training promotes automaticity of a fundamental laparoscopic skill without compromising the rate of skill learning.

BACKGROUND: A defining characteristic of expertise is automated performance of skills, which frees attentional capacity to better cope with some common intraoperative stressors. There is a paucity of research on how best to foster automated performance by surgical trainees. This study examined the use of a multitask training approach to promote automated, robust laparoscopic skills. METHODS: Eighty-one medical students completed training of a fundamental laparoscopic task in either a traditional single-task training condition or a novel multitask training condition. Following training, participants' laparoscopic performance was tested in a retention test, two stress transfer tests (distraction and time pressure) and a secondary task test, which was included to evaluate automaticity of performance. The laparoscopic task was also performed as part of a formal clinical examination (OSCE). RESULTS: The training groups did not differ in the number of trials required to reach task proficiency (p = .72), retention of skill (ps > .45), or performance in the clinical examination (p = .14); however, the groups did differ with respect to the secondary task (p = .016). The movement efficiency (number of hand movements) of single-task trainees, but not multitask trainees, was negatively affected during the secondary task test. The two stress transfer tests had no discernable impact on the performance of either training group. CONCLUSION: Multitask training was not detrimental to the rate of learning of a fundamental laparoscopic skill and added value by providing resilience in the face of a secondary task load, indicative of skill automaticity. Further work is needed to determine the extent of the clinical utility afforded by multitask training.

Cathodal Transcranial Direct Current Stimulation Over Left Dorsolateral Prefrontal Cortex Area Promotes Implicit Motor Learning in a Golf Putting Task.

BACKGROUND: Implicit motor learning is characterized by low dependence on working memory and stable performance despite stress, fatigue, or multi-tasking. However, current paradigms for implicit motor learning are based on behavioral interventions that are often task-specific and limited when applied in practice. OBJECTIVE: To investigate whether cathodal transcranial direct current stimulation (tDCS) over the left dorsolateral prefrontal cortex (DLPFC) area during motor learning suppressed working memory activity and reduced explicit verbal-analytical involvement in movement control, thereby promoting implicit motor learning. METHODS: Twenty-seven healthy individuals practiced a golf putting task during a Training Phase while receiving either real cathodal tDCS stimulation over the left DLPFC area or sham stimulation. Their performance was assessed during a Test phase on another day. Verbal working memory capacity was assessed before and after the Training Phase, and before the Test Phase. RESULTS: Compared to sham stimulation, real stimulation suppressed verbal working memory activity after the Training Phase, but enhanced golf putting performance during the Training Phase and the Test Phase, especially when participants were required to multi-task. CONCLUSION: Cathodal tDCS over the left DLPFC may foster implicit motor learning and performance in complex real-life motor tasks that occur during sports, surgery or motor rehabilitation.

Implicit motor learning promotes neural efficiency during laparoscopy.

BACKGROUND: An understanding of differences in expert and novice neural behavior can inform surgical skills training. Outside the surgical domain, electroencephalographic (EEG) coherence analyses have shown that during motor performance, experts display less coactivation between the verbal-analytic and motor planning regions than their less skilled counterparts. Reduced involvement of verbal-analytic processes suggests greater neural efficiency. The authors tested the utility of an implicit motor learning intervention specifically devised to promote neural efficiency by reducing verbal-analytic involvement in laparoscopic performance. METHODS: In this study, 18 novices practiced a movement pattern on a laparoscopic trainer with either conscious awareness of the movement pattern (explicit motor learning) or suppressed awareness of the movement pattern (implicit motor learning). In a retention test, movement accuracy was compared between the conditions, and coactivation (EEG coherence) was assessed between the motor planning (Fz) region and both the verbal-analytic (T3) and the visuospatial (T4) cortical regions (T3-Fz and T4-Fz, respectively). RESULTS: Movement accuracy in the conditions was not different in a retention test (P = 0.231). Findings showed that the EEG coherence scores for the T3-Fz regions were lower for the implicit learners than for the explicit learners (P = 0.027), but no differences were apparent for the T4-Fz regions (P = 0.882). CONCLUSIONS: Implicit motor learning reduced EEG coactivation between verbal-analytic and motor planning regions, suggesting that verbal-analytic processes were less involved in laparoscopic performance. The findings imply that training techniques that discourage nonessential coactivation during motor performance may provide surgeons with more neural resources with which to manage other aspects of surgery.

Target-directed visual attention is a prerequisite for action-specific perception.

Witt et al. (2008) have recently shown that golfers who putt with more success perceive the hole to be bigger than golfers who putt with less success. In three experiments, we systematically examined whether this phenomenon, labelled action-specific perception, depends on directing visual attention towards the action target. In Experiment 1 we replicated previously reported action-specific effects on perception in golf putting. In Experiments 2 and 3 we directly assessed whether action-specific effects on perception in golf putting are dependent on focusing visual attention on the target. To this end, the participants performed the putting task while visual attention towards the target was either completely withheld (Experiment 2) or divided over the target and other task-relevant objects (Experiment 3). No action-specific effects were found when visual attention towards the action target was occluded or partially diverted from the target. Together, our results provide evidence to suggest that focusing visual attention on the target while performing the action is a prerequisite for the emergence of action-specific perception.