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To examine whether transcranial direct current stimulation (tDCS) applied over the posterior parietal cortex (PPC) improves visuospatial attention in stroke patients with left visuospatial neglect.
Patients were randomly assigned to 1 of 3 treatment groups: anodal tDCS over the right PPC, cathodal tDCS over the left PPC, or sham tDCS. Each patient underwent 15 sessions of tDCS (5 sessions per week for 3 weeks; 2 mA for 30 minutes in each session). Outcome measures were assessed before treatment and 1 week after completing the treatment.
From pre- to post-treatment, there was an improvement in the motor-free visual perception test (MVPT), line bisection test (LBT), star cancellation test (SCT), Catherine Bergego Scale (CBS), Korean version of Modified Barthel Index (K-MBI), and Functional Ambulation Classification in all 3 groups. Improvements in the MVPT, SCT, and LBT were greater in the anodal and cathodal groups than in the sham group. However, improvements in other outcomes were not significantly different between the 3 groups, although there was a tendency for improved CBS or K-MBI scores in the anodal and cathodal groups, as compared with the sham group.
The study results indicated that the facilitatory effect of anodal tDCS applied over the right PPC, and the inhibitory effect of cathodal tDCS applied over the left PPC, improved symptoms of visuospatial neglect. Thus, tDCS could be a successful adjuvant therapeutic modality to recover neglect symptom, but this recovery might not lead to improvements in activities of daily living function and gait function.
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To investigate the effects of simultaneous, bihemispheric, dual-mode stimulation using repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) on motor functions and cortical excitability in healthy individuals.
Twenty-five healthy, right-handed volunteers (10 men, 15 women; mean age, 25.5 years) were enrolled. All participants received four randomly arranged, dual-mode, simultaneous stimulations under the following conditions: condition 1, high-frequency rTMS over the right primary motor cortex (M1) and sham tDCS over the left M1; condition 2, high-frequency rTMS over the right M1 and anodal tDCS over the left M1; condition 3, high-frequency rTMS over the right M1 and cathodal tDCS over the left M1; and condition 4, sham rTMS and sham tDCS. The cortical excitability of the right M1 and motor functions of the left hand were assessed before and after each simulation.
Motor evoked potential (MEP) amplitudes after stimulation were significantly higher than before stimulation, under the conditions 1 and 2. The MEP amplitude in condition 2 was higher than both conditions 3 and 4, while the MEP amplitude in condition 1 was higher than condition 4. The results of the Purdue Pegboard test and the box and block test showed significant improvement in conditions 1 and 2 after stimulation.
Simultaneous stimulation by anodal tDCS over the left M1 with high-frequency rTMS over the right M1 could produce interhemispheric modulation and homeostatic plasticity, which resulted in modulation of cortical excitability and motor functions.
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To investigate the analgesic effect of transcranial direct current stimulation (tDCS) over the primary motor (M1), dorsolateral prefrontal cortex (DLPFC), and sham tDCS in patients with painful diabetic polyneuropathy (PDPN).
Patients with PDPN (n=60) were divided randomly into the three groups (n=20 per group). Each group received anodal tDCS with the anode centered over the left M1, DLPFC, or sham stimulation for 20 minutes at intensity of 2 mA for 5 consecutive days. A blinded physician rated the patients' pain using a visual analog scale (VAS), Clinical Global Impression (CGI) score, anxiety score, sleep quality, Beck Depression Inventory (BDI), and the pain threshold (PT) to pressure.
After the tDCS sessions, the M1 group showed a significantly greater reduction in VAS for pain and PT versus the sham and DLPFC groups (p<0.001). The reduction in VAS for pain was sustained after 2 and 4 weeks of follow-up in the M1 group compared with the sham group (p<0.001, p=0.007). Significant differences were observed among the three groups over time in VAS for pain (p<0.001), CGI score (p=0.01), and PT (p<0.001). No significant difference was observed among the groups in sleep quality, anxiety score, or BDI score immediately after tDCS.
Five daily sessions of tDCS over the M1 can produce immediate pain relief, and relief 2- and 4-week in duration in patients with PDPN. Our findings provide the first evidence of a beneficial effect of tDCS on PDPN.
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To investigate any additional effect of dual transcranial direct current stimulation (tDCS) compared with single tDCS in chronic stroke patients with aphasia.
Eleven chronic stroke patients (aged 52.6±13.4 years, nine men) with aphasia were enrolled. Single anodal tDCS was applied over the left inferior frontal gyrus (IFG) and a cathodal electrode was placed over the left buccinator muscle. Dual tDCS was applied as follows: 1) anodal tDCS over the left IFG and cathodal tDCS over the left buccinator muscle and 2) cathodal tDCS over the right IFG and anodal tDCS over the right buccinator muscle. Each tDCS was delivered for 30 minutes at a 2-mA intensity. Speech therapy was provided during the last 15 minutes of the tDCS. Before and after the stimulation, the Korean-Boston Naming Test and a verbal fluency test were performed.
The dual tDCS produced a significant improvement in the response time for the Korean-Boston Naming Test compared with the baseline assessment, with a significant interaction between the time and type of interventions. Both single and dual tDCS produced a significant improvement in the number of correct responses after stimulation with no significant interaction. No significant changes in the verbal fluency test were observed after single or dual tDCS.
The results conveyed that dual tDCS using anodal tDCS over the left IFG and cathodal tDCS over the right IFG may be more effective than a single anodal tDCS over the left IFG.
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To investigate the effects of transcranial direct current stimulation (tDCS) applied over the prefrontal cortex on the improvement of verbal, visuospatial working memory and naming in healthy adults.
Thirty two healthy adults (15 males and 17 females, mean age 37.3±13.0 years) were enrolled in this study. The subjects were divided into four groups randomly. They underwent sham or anodal tDCS over the left or right prefrontal cortex, for 20 minutes at a direct current of 1 mA. Before and immediately after tDCS, the subjects performed the Korean version of the mini-mental state exam (K-MMSE) and stroop test (color/word/interference) for the screening of cognitive function. For working memory and language evaluation, the digit span test (forward/backward), the visuospatial attention test in computer assisted cognitive program (CogPack®) and the Korean-Boston Naming Test (K-BNT) were assessed before tDCS, immediately after tDCS, and 2 weeks after tDCS.
The stroop test (word/interference), backward digit span test and K-BNT were improved in the left prefrontal tDCS group compared with that of the sham group (p<0.05). The stroop test (interference) and visuospatial attention test were in the right prefrontal tDCS group compared with that of the sham group (p<0.05). Their improvement lasted for 2 weeks after stimulation.
tDCS can induce verbal working memory improvement and naming facilitation by stimulating the left prefrontal cortex. It can also improve the visuospatial working memory by stimulating the right prefrontal cortex. Further studies which are lesion and symptom specific tDCS treatment for rehabilitation of stroke can be carried out.
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To evaluate motor excitability and hand function on the non-dominant side according to the polarity of transcranial direct current stimulation (tDCS) on the motor cortex in a healthy person.
tDCS was applied to the hand motor cortex for 15 minutes at an intensity of 1 mA in 28 healthy right-handed adults. Subjects were divided randomly into four groups: an anodal tDCS of the non-dominant hemisphere group, a cathodal tDCS of the non-dominant hemisphere group, an anodal tDCS of the dominant hemisphere group, and a sham group. We measured the motor evoked potential (MEP) in the abductor pollicis brevis and Jabsen-Taylor hand function test (JTT) in the non-dominant hand prior to and following tDCS. All study procedures were done under double-blind design.
There was a significant increase in the MEP amplitude and a significant improvement in the JTT in the non-dominant hand following anodal tDCS of the non-dominant hemisphere (p<0.05). But there was no change in JTT and a significant decrease in the MEP amplitude in the non-dominant hand following cathodal tDCS on the non-dominant hemisphere and anodal tDCS of the dominant hemisphere.
Non-dominant hand function is improved by increased excitability of the motor cortex. Although motor cortex excitability is decreased in a healthy person, non-dominant hand function is maintained. A homeostatic mechanism in the brain might therefore be involved in preserving this function. Further studies are warranted to examine brain functions to clarify this mechanism.
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To determine factors associated with good responses to speech therapy combined with transcranial direct current stimulation (tDCS) in aphasic patients after stroke.
The language function was evaluated using Korean version of Western aphasia battery (K-WAB) before and after speech therapy with tDCS in 37 stroke patients. Patients received speech therapy for 30 minutes over 2 to 3 weeks (10 sessions) while the cathodal tDCS was performed to the Brodmann area 45 with 1 mA for 20 minutes. We compared the improvement of aphasia quotient % (AQ%) between two evaluation times according to age, sex, days after onset, stroke type, aphasia type, brain lesion confirmed by magnetic resonance image and initial severity of aphasia. The factors related with good responses were also checked.
AQ% improved from pre- to post-therapy (14.94±6.73%, p<0.001). AQ% improvement was greater in patients with less severe, fluent type of aphasia who received treatment before 30 days since stroke was developed (p<0.05). The adjusted logistic regression model revealed that patients with hemorrhagic stroke were more likely to achieve good responses (odds ratio=4.897, p<0.05) relative to infarction. Initial severity over 10% in AQ% was also found to be significantly associated with good improvement (odds ratio=8.618, p<0.05).
Speech therapy with tDCS was established as a treatment tool for aphasic patients after stroke. Lower initial severity was associated with good responses.
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