treating cognitive impairment , along with motor recovery and improving performance in daily activities , is one of the key focus areas of stroke rehabilitation .
as cognition is closely related to patient motivation and motor function improvement , implementing cognitive function treatment in a timely and effective manner is crucial for the overall success of poststroke rehabilitation .
previous reports showed 25%-40% of patients suffer from dementia by three months after stroke , and the number increased to 50%-75% when patients with minor symptoms of cognitive impairment are included [ 2 - 4 ] . among patients with brain lesions ,
memory disturbance is commonly a critical challenge in rehabilitating patients to enable them to return to active participation in society and the workforce .
research has suggested that rehabilitation programs designed to maximize neuroplasticity are effective for improving memory functions in these patients .
recently , transcranial direct - current stimulation ( tdcs ) and repetitive transcranial magnetic stimulation ( rtms ) , noninvasive methods for stimulating the cerebral cortex , have been intensively studied as a treatment for brain injury . while both modalities are used to treat brain injury ,
tdcs is the preferred method , as it allows simultaneous application of brain stimulation and conventional rehabilitation .
concluded that applying tdcs to the brain region improved motor functions and increased motor cortex excitability .
recent studies also suggested that tdcs was useful in treating cognitive dysfunction , and improving attention , memory , and executive function [ 7 - 9 ] .
however , there are still insufficient data to confirm its effect on the cognitive functions of stroke patients .
thus , in this study , we determined the effectiveness of tdcs in cognitive recovery in acute and subacute stroke patients .
we selected stroke patients with cognitive impairment and a score of  27 on the korean version of mini mental state exam ( k - mmse ) from patients treated at the department of rehabilitation medicine , asan medical center , from october 1 , 2010 to march 30 , 2012 .
the guardians of the patients indicated that the patients had experienced their first stroke , and had no previous history of abnormal cognitive functions .
patients who were classified as acute or subacute , within 6 months from their stroke , and who showed no damage to their temporal lobe on magnetic resonance imaging , were selected .
subjects were then included when they were willing and available for five treatment sessions per week .
patients with apraxia , aphasia , and neglect were excluded , given that these factors may have an impact on the outcome of cognitive function tests . for the safety of patients , we excluded those who had a history of craniectomy or seizure .
we used the double - blind method to randomly divide the subjects into three test groups : ( 1 ) the left fronto - temporal anode stimulation ( left - ftas ) group , ( 2 ) the right fronto - temporal anode stimulation ( right - ftas ) group , and ( 3 ) the sham group .
patients in each group received tdcs treatment for 30 min , five times a week , for 3 weeks .
the treatments were performed using a phoresor ii auto model pm850 ( iomed , salt lake city , ut , usa ) , an fda - approved device , with 5  5 cm sponge electrodes attached to the patient s scalp .
the intensity of the current was set at 2 ma , which was confirmed as safe by iyer et al .
tdcs anodal electrodes were placed according to the 10 - 20 international eeg system , at t3 for the left - ftas group and at t4 for the right - ftas group . for the sham group ,
sponge electrodes were attached using the same method as for the left - ftas group , but without any current running . the cognitive rehabilitation program used in the study was comcog ( maxmedica inc . ,
seoul , korea ) , with the focus on attention and memory improvement for cognitive disorder patients .
the subjects were evaluated before the treatment and after completing the 3-week program , using the k - mmse and computerized neurocognitive function tests ( cnt , maxmedica , seoul , korea ) to assess cognitive function , and the korean version of the modified barthel index ( k - mbi ) to assess activities of daily living .
the cnt included visual and auditory continuous performance tests ( cpts ) to evaluate continuous concentration on visual and auditory stimuli .
the kruskal - wallis test was used to test the homogeneity among the three groups , and the wilcoxon signed - rank test was used to analyze the preand post - treatment data for each test group .
the kruskal - wallis test was used to compare the three test groups , and the mann - whitney test was used as the follow - up test .
we selected stroke patients with cognitive impairment and a score of  27 on the korean version of mini mental state exam ( k - mmse ) from patients treated at the department of rehabilitation medicine , asan medical center , from october 1 , 2010 to march 30 , 2012 .
the guardians of the patients indicated that the patients had experienced their first stroke , and had no previous history of abnormal cognitive functions .
patients who were classified as acute or subacute , within 6 months from their stroke , and who showed no damage to their temporal lobe on magnetic resonance imaging , were selected .
subjects were then included when they were willing and available for five treatment sessions per week .
patients with apraxia , aphasia , and neglect were excluded , given that these factors may have an impact on the outcome of cognitive function tests . for the safety of patients
we used the double - blind method to randomly divide the subjects into three test groups : ( 1 ) the left fronto - temporal anode stimulation ( left - ftas ) group , ( 2 ) the right fronto - temporal anode stimulation ( right - ftas ) group , and ( 3 ) the sham group .
patients in each group received tdcs treatment for 30 min , five times a week , for 3 weeks .
the treatments were performed using a phoresor ii auto model pm850 ( iomed , salt lake city , ut , usa ) , an fda - approved device , with 5  5 cm sponge electrodes attached to the patient s scalp .
the intensity of the current was set at 2 ma , which was confirmed as safe by iyer et al .
tdcs anodal electrodes were placed according to the 10 - 20 international eeg system , at t3 for the left - ftas group and at t4 for the right - ftas group . for the sham group , sponge electrodes were attached using the same method as for the left - ftas group , but without any current running . the cognitive rehabilitation program used in the study was comcog ( maxmedica inc . ,
seoul , korea ) , with the focus on attention and memory improvement for cognitive disorder patients .
the subjects were evaluated before the treatment and after completing the 3-week program , using the k - mmse and computerized neurocognitive function tests ( cnt , maxmedica , seoul , korea ) to assess cognitive function , and the korean version of the modified barthel index ( k - mbi ) to assess activities of daily living . the cnt included visual and auditory continuous performance tests ( cpts ) to evaluate continuous concentration on visual and auditory stimuli .
the kruskal - wallis test was used to test the homogeneity among the three groups , and the wilcoxon signed - rank test was used to analyze the preand post - treatment data for each test group .
the kruskal - wallis test was used to compare the three test groups , and the mann - whitney test was used as the follow - up test .
the subjects for this study included : ( 1 ) six male and nine female patients in the left - ftas group , ( 2 ) seven male and eight female patients in the right - ftas group , and ( 3 ) seven male and eight female patients in the sham group .
the mean age of patients in each group was as follows : ( 1 ) 60.9 12.9 years for the left - ftas group , ( 2 ) 58.915.0 years for the right - ftas group , and ( 3 ) 68.514.6 years for the control group , with no significant differences between the groups .
the mean time elapsed from the onset of stroke to the start of the treatment program was : ( 1 ) 42.231.9 days for the left - ftas group , ( 2 ) 38.127.0 days for the right - ftas group , and ( 3 ) 39.529.6 days for the sham group , with no significant differences between the groups ( table 1 ) .
the results from post - treatment cnt suggested that the left - ftas group showed significant improvement in the backward digit span test , the verbal learning test - delayed recall , a visual span test , and the k - mmse .
all three groups showed significant improvement in k - mbi scores ( table 2 ) .
comparison of pre- and post - treatment data for each group suggests that the left - ftas group showed significant improvement in auditory memory , compared to the other groups .
however , there were no significant differences between the groups in terms of visual memory and attention .
there were no differences between the groups in terms of k - bmi ( table 3 ) .
the subjects for this study included : ( 1 ) six male and nine female patients in the left - ftas group , ( 2 ) seven male and eight female patients in the right - ftas group , and ( 3 ) seven male and eight female patients in the sham group .
the mean age of patients in each group was as follows : ( 1 ) 60.9 12.9 years for the left - ftas group , ( 2 ) 58.915.0 years for the right - ftas group , and ( 3 ) 68.514.6 years for the control group , with no significant differences between the groups .
the mean time elapsed from the onset of stroke to the start of the treatment program was : ( 1 ) 42.231.9 days for the left - ftas group , ( 2 ) 38.127.0 days for the right - ftas group , and ( 3 ) 39.529.6 days for the sham group , with no significant differences between the groups ( table 1 ) .
the results from post - treatment cnt suggested that the left - ftas group showed significant improvement in the backward digit span test , the verbal learning test - delayed recall , a visual span test , and the k - mmse .
all three groups showed significant improvement in k - mbi scores ( table 2 ) .
comparison of pre- and post - treatment data for each group suggests that the left - ftas group showed significant improvement in auditory memory , compared to the other groups .
however , there were no significant differences between the groups in terms of visual memory and attention .
there were no differences between the groups in terms of k - bmi ( table 3 ) .
the objective of this study was to determine the effect of tdcs treatment on the temporal lobe in terms of cognitive recovery of poststroke patients . to date
, only a small number of studies have been done on tdcs as a treatment method for cognitive impairment . while montie et al .
suggested that cathode stimulation to the left fronto - temporal lobe resulted in improvement in naming in aphasia , other studies concluded that anode stimulation to the left perisylvian region resulted improvement in word memory in healthy patients .
boggio et al . also concluded that anode stimulation to the left fronto - temporal lobe helped to improve memory performance in alzheimer disease .
the results of our study suggested that anodal stimulation to the left fronto - temporal lobe improved auditory memory , confirming the conclusion of earlier studies , although the treatment did not affect visual memory .
cnt test showed that the treatment had been positively effective in all areas , but other three groups , excluding auditory memory , showed no statistical difference .
only few studies have been done on the effect of tdcs on cognitive function in stroke patients . while kang et al .  
suggested that anode stimulation at the dorso - lateral prefrontal cortex improved attention , kim et al .   concluded that rtms on the same region was only effective in treating depression , and
there have been two reports on patients with stroke who experienced linguistic improvement , but these studies only involved 10 and 13 patients , respectively .
no studies have clearly defined the effects of noninvasive brain stimulation on the cognitive function of stroke patients .
studies have discovered that tdcs affects the brain by activating n - methyl - d - aspartic acid ( nmda ) receptors and suppressing the cerebral cortex via gamma - aminobutyric acid ( gaba ) receptors . the effect of tdcs is known to last for approximately 90 minutes , during which the cerebral cortex remains excited , but there are too few studies to be able to draw conclusions on the accumulated effect .
this report showed that marked improvements are noted after 3 weeks of tdcs treatment , but the accumulated effect could not be determined because serial cognitive function was not assessed .
the findings from this study may have been limited by the small number of patients in each test group .
cerebral infarction and hemorrhage were both included and lesions varied largely , so that spontaneous recovery could not be fully excluded . as well as excluding cathode stimulation from the treatment .
additionally , the subjects were not tested for depression , which may have affected the outcome . as it has been suggested that depression is prominent among stroke patients and as depression may affect attention and memory ,
the possibility remains that the study may have included patients with depression , whose depression symptoms were affected by tdcs , which then subsequently resulted in improved cognitive function . furthermore , poststroke apathy can affect cognitive function , but this could not be addressed in this study . since the subjects were evaluated for cognitive performance at 24 hours after completion of the 3-week treatment program , the long - term effect of tdcs treatment remains undetermined .
moreover , we excluded patients with abnormal cognitive function based on the guardian s statement , but we had not tested the cognitive function of patients before they suffered their stroke , which may have an impact on the study result
. nevertheless , this study confirmed that tdcs is effective in treating poststroke cognitive impairment .
we were also able to conclude that stimulation on the temporal lobe , as well as on the prefrontal lobe , as suggested by earlier studies , is helpful in cognitive recovery .
the results from this study confirmed that applying tdcs to the left temporal lobe effectively improved auditory memory of patients with poststroke cognitive impairment .
we concluded that tdcs can be employed as a treatment sub - protocol in a cognitive treatment program .
however , further studies with a larger subject pool and various stimulation methods should be conducted to confirm these findings .
 background and purposeto investigate whether transcranial direct - current stimulation ( tdcs ) can improve cognition in stroke patients.methodsforty-five stroke patients ( 20 males and 25 females , average age : 62.7 years ) with cognitive dysfunction were included in this prospective , double - blinded , randomized case  
 control study . 
 all patients were right - handed and the mean elapsed time after stroke was 39.3 days . 
 three different treatments groups were used : ( 1 ) anodal stimulation of the left anterior temporal lobe , ( 2 ) anodal stimulation of the right anterior temporal lobe , and ( 3 ) sham stimulation . 
 tdcs was delivered for 30 minutes at 2 ma with 25 cm2 electrodes , five times / week , for a total of 3 weeks , using a phoresor ii auto model pm 850 ( iomed ) . 
 the evaluation of cognitive impairment was based on a computerized neuropsychological test ( cnt ) , korean mini - mental state examination ( k - mmse ) . 
 the korean version of the modified barthel index ( k - mbi ) was used to assess activities of daily living functionality . 
 these evaluations were conducted in all patients before and after treatment.resultseach group included 15 patients . 
 pre - treatment evaluation showed no significant differences between the three groups for any of the parameters . 
 there was significant improvement in the verbal learning test on the cnt in the left anodal stimulation group ( p < 0.05 ) . 
 there were , however , no significant differences in the k - mmse or k - mbi scores among the three groups.conclusionsthese results demonstrated the beneficial effects of anodal tdcs on memory function . 
 thus , tdcs can successfully be used as a treatment modality for patients with cognitive dysfunction after stroke . 
Introduction
Methods
Subjects
Treatments
Statistical analysis
Results
General characteristics of the subjects
Pre- and post-treatment comparison
Comparison between the three groups
Discussion
Conclusions