Therapeutic Effects of Transcranial Magnetic Stimulation on Visuospatial Neglect Revealed With Event-Related Potentials.

This study aimed to investigate changes in attention processing after low-frequency repetitive transcranial magnetic stimulation (rTMS) over the left posterior parietal cortex to better understand its role in visuospatial neglect (VSN) rehabilitation. The current study included 10 subacute stroke patients with VSN consecutively recruited from the inpatient stroke rehabilitation center at Xuanwu Hospital (the teaching hospital affiliated with Capital Medical University) between March and November 2019. All patients performed a battery of tasks (including line bisection, line cancellation, and star cancellation tests) two weeks before treatment and at the beginning and end of treatment; the attentive components of the test results were analyzed. In addition, low-frequency rTMS was used to stimulate the left posterior parietal cortex for 14 days and event-related potential data were collected before and after the stimulation. Participants were evaluated using a target-cue paradigm and pencil-paper tests. No significant differences were detected on the battery of tasks before rTMS. However, we found that rTMS treatment significantly improved the response times and accuracy rates of patients with VSN. After rTMS, the treatment side (left) amplitude of P300 following an event-related potential was higher than that before treatment (left target, p = 0.002; right target, p = 0.047). Thus, our findings suggest that rTMS may be an effective treatment for VSN. The observed increase in event-related potential amplitude supports the hypothesized compensational role of the contralesional hemisphere in terms of residual performance. Our results provide electrophysiological evidence that may help determine the mechanisms mediating the therapeutic effects of rTMS.

Recovery from prolonged disorders of consciousness: A dual-center prospective cohort study in China.

BACKGROUND: Recent innovations in intensive care have improved the prognosis of patients with severe brain injuries and brought more patients with disorders of consciousness (DoC). Data are lacking regarding the long-term outcomes of those patients in China. It is necessary to study the long-term outcomes of patients with prolonged DoC in light of many factors likely to influence crucial decisions about their care and their life. AIM: To present the preliminary results of a DoC cohort. METHODS: This was a two-center prospective cohort study of inpatients with vegetative state (VS)/unresponsive wakefulness syndrome (UWS). The study outcomes were the recovery from VS/UWS to minimally conscious state (MCS) and the long-term status of patients with prolonged DoC considered in VS/UWS or MCS for up to 6 years. The patients were evaluated using the Glasgow coma scale, coma recovery scale-revised, and Glasgow outcome scale. The endpoint of follow-up was recovery of full consciousness or death. The changes in the primary clinical outcome improvement in clinical diagnosis were evaluated at 12 mo compared with baseline. RESULTS: The study population included 93 patients (62 VS/UWS and 31 MCS). The post-injury interval range was 28-634 d. Median follow-up was 20 mo (interquartile range, 12-37 mo). At the endpoint, 33 transitioned to an emergence from MCS or full consciousness, eight had a locked-in syndrome, and there were 35 patients remaining in a VS/UWS and 11 in an MCS. Seven (including one locked-in syndrome) patients (7.5%) died within 12 mo of injury. Compared with the unresponsive group (n = 52) at 12 mo, the responsive group (n = 41) had a higher proportion of males (87.8% vs 63.5%, P = 0.008), shorter time from injury (median, 40.0 d vs 65.5 d, P = 0.006), higher frequency of vascular etiology (68.3% vs 38.5%, P = 0.007), higher Glasgow coma scale score at admission (median, 9 vs 6, P < 0.001), higher coma recovery scale-revised score at admission (median, 9 vs 2.5, P < 0.001), at 1 mo (median, 14 vs 5, P < 0.001), and at 3 mo (median, 20 vs 6, P < 0.001), lower frequency of VS/UWS (36.6% vs 90.0%, P < 0.001), and more favorable Glasgow outcome scale outcome (P < 0.001). CONCLUSION: Patients with severe DoC, despite having strong predictors of poor prognosis, might recover consciousness after a prolonged time of rehabilitation. An accurate initial diagnosis of patients with DoC is critical for predicting outcome and a long-term regular follow-up is also important.

Visual-spatial neglect after right-hemisphere stroke: behavioral and electrophysiological evidence.

BACKGROUND: Visual-spatial neglect (VSN) is a neuropsychological syndrome, and right-hemisphere stroke is the most common cause. The pathogenetic mechanism of VSN remains unclear. This study aimed to investigate the behavioral and event-related potential (ERP) changes in patients with or without VSN after right-hemisphere stroke. METHODS: Eleven patients with VSN with right-hemisphere stroke (VSN group) and 11 patients with non-VSN with right-hemisphere stroke (non-VSN group) were recruited along with one control group of 11 age- and gender-matched healthy participants. The visual-spatial function was evaluated using behavioral tests, and ERP examinations were performed. RESULTS: The response times in the VSN and non-VSN groups were both prolonged compared with those of normal controls (P < 0.001). In response to either valid or invalid cues in the left side, the accuracy in the VSN group was lower than that in the non-VSN group (P < 0.001), and the accuracy in the non-VSN group was lower than that in controls (P < 0.05). The P1 latency in the VSN group was significantly longer than that in the control group (F[2, 30] = 5.494, P = 0.009), and the N1 amplitude in the VSN group was significantly lower than that in the control group (F[2, 30] = 4.343, P = 0.022). When responding to right targets, the left-hemisphere P300 amplitude in the VSN group was significantly lower than that in the control group (F[2, 30] = 4.255, P = 0.025). With either left or right stimuli, the bilateral-hemisphere P300 latencies in the VSN and non-VSN groups were both significantly prolonged (all P < 0.05), while the P300 latency did not differ significantly between the VSN and non-VSN groups (all P > 0.05). CONCLUSIONS: Visual-spatial attention function is impaired after right-hemisphere stroke, and clinicians should be aware of the subclinical VSN. Our findings provide neuroelectrophysiological evidence for the lateralization of VSN.

Low frequency repetitive transcranial magnetic stimulation improves motor dysfunction after cerebral infarction.

Low frequency (≤ 1 Hz) repetitive transcranial magnetic stimulation (rTMS) can affect the excitability of the cerebral cortex and synaptic plasticity. Although this is a common method for clinical treatment of cerebral infarction, whether it promotes the recovery of motor function remains controversial. Twenty patients with cerebral infarction combined with hemiparalysis were equally and randomly divided into a low frequency rTMS group and a control group. The patients in the low frequency rTMS group were given 1-Hz rTMS to the contralateral primary motor cortex with a stimulus intensity of 90% motor threshold, 30 minutes/day. The patients in the control group were given sham stimulation. After 14 days of treatment, clinical function scores (National Institute of Health Stroke Scale, Barthel Index, and Fugl-Meyer Assessment) improved significantly in the low frequency rTMS group, and the effects were better than that in the control group. We conclude that low frequency (1 Hz) rTMS for 14 days can help improve motor function after cerebral infarction.

Application of noninvasive brain stimulation for post-stroke dysphagia rehabilitation.

Noninvasive brain stimulation (NIBS), commonly consisting of transcranial magnetic stimulation (TMS), transcranial direct-current stimulation (tDCS), as well as paired associative stimulation (PAS), has attracted increased interest and been applied experimentally in the treatment of post-stroke dysphagia (PSD). This review presented a synopsis of the current research for the application of NIBS on PSD. The intention here was to understand the current research progress and limitations in this field and to stimulate potential research questions not yet investigated for the application of NIBS on patients with PSD. Here we successively reviewed advances of repetitive TMS (rTMS), tDCS, and PAS techniques on both healthy participants and PSD patients in three aspects, including scientific researches about dysphagia mechanism, applied studies about stimulation parameters, and clinical trials about their therapeutic effects. The techniques of NIBS, especially rTMS, have been used by the researchers to explore the different mechanisms between swallowing recovery and extremity rehabilitation. The key findings included the important role of intact hemisphere reorganization for PSD recovery, and the use of NIBS on the contra-lesional side as a therapeutic potential for dysphagia rehabilitation. Though significant results were achieved in most studies by using NIBS on swallowing rehabilitation, it is still difficult to draw conclusions for the efficacy of these neurostimulation techniques, considering the great disparities between studies.

Brain dynamic mechanisms of scale effect in visual spatial attention.

The dynamic mechanisms of the early event-related potential scale effect of different attentive regions in the brain was studied. The paradigm of this experiment is the precue-target visual search paradigm by event-related potential technique. The results showed that the reaction time was shortened with the reduction of cue scale, a cue to how big the search area would be, and fixed target stimulus, while the amplitudes of P1 and N1 components of event-related potentials increased. These results not only provided the electrophysiological evidences that supported the zoom-lens theory, but also indicated that the zoom-lens effect happened at the early selected attention period. The results also showed that there existed two kinds of separation in the P2 effect.

Connecting the P300 to the diagnosis and prognosis of unconscious patients.

The residual consciousness of unconscious patients can be detected by studying the P300, a wave among event-related potentials. Previous studies have applied tones, the subject's name and other names as stimuli. However, the results were not satisfactory. In this study, we changed the constituent order of subjects' two-character names to create derived names. The subject's derived names, together with tones and their own names, were used as auditory stimuli in event-related potential experiments. Healthy controls and unconscious patients were included in this study and made to listen to these auditory stimuli. In the two paradigms, a sine tone followed by the subject's own name and the subject's derived name followed by the subject's own name were used as standard and deviant stimuli, respectively. The results showed that all healthy controls had the P300 using both paradigms, and that the P300 in the second paradigm had a longer latency and two peaks. All minimally conscious state patients had the P300 in the first paradigm and the majority of them had the P300 in the second paradigm. Most vegetative state patients had no P300. Patients who showed the P300 in the two paradigms had more residual consciousness, and patients with the two-peak P300 had a higher probability of awakening within a short time. Our experimental findings suggest that the P300 event-related potential could reflect the conscious state of unconscious patients.

[Early scale effects of the visual spatial attention].

OBJECTIVE: To investigate the visual attention mechanisms of brain, the "cue-target" experimental paradigm was adopted, and the attended range was cued by different Chinese characters. METHOD: Sixteen healthy young participants (8 male and 8 female, 19-24 years old with an average of 21) served as the subjects. The stimulus sequence was "background-cue-target". The background was comprised of three homocentric white circles. Cue was the Chinese character " large", "median" and " small ". There were 8 capital English letters in each circle, which formed three homocentric circles. "T" was designed as the target stimulus. When the cue was large, the target "T" appeared within the three circles. When the cue was medium, "T" appeared within the medium and small circles. When the cue was small, the T maybe appeared only within the small circle. RESULT: The reaction time became short with the decrease of the cue scale, while P1 and N1 components amplitudes increased. CONCLUSION: These results not only provided the electrophysiological evidence for the spot light theory, but also indicated that the spot-light effect happened at the early period of the information processing.

[Aging study of event-related potential on visual spatial attention precued by Chinese words].

OBJECTIVE: Based on the visual experimental paradigm "precue-target", the search range should be affected by different Chinese characters and the dynamic mechanisms of aging in the brain on the visual attention were investigated. METHOD: 16 young and 16 old subjects participated the experiment. Cue was comprised of three Chinese words "Large", or "Median" or "Small." The letter "T" was designed as the target stimulus. When the cue was the "large", "T" may appear within 3 circles. When the cue was the "median", "T" may appear within either the median and small circles. When the cue was small, the target "T" may appear only within the small circle. RESULT: The reaction time (RT) of the two groups of subjects became quick with the reduction of the cue size, while amplitudes of the P1 and N1 component of ERPs increased with the decrease of the cue scale. Old subjects showed longer RT than younger subjects did. The posterior P1 was enhanced significantly and the N1 was inhibited obviously in the old group. The P2 was manifested as significantly inhibitory effect not only in the amplitude but also in the abnormal and unstable waveform. CONCLUSION: The cognitive function of elderly subjects declined in the task of visual spatial attention. We demonstrated for the first time that the P2 was manifested as significantly inhibitory effect, which suggested that the age-related reduction could lead to dysfunction in the anterior scalp to visual spatial attention (voluntary attention).

Evaluation of spasticity after stroke by using ultrasound to measure the muscle architecture parameters: a clinical study.

OBJECTIVE: This study aims to compare the difference and the change trend of Muscle Architecture Parameters (MAP) between spastic and normal muscle tone patients after stroke, and analysis the application and value of Muscle Architecture Parameters in evaluating spasticity after stroke. METHODS: 41 stroke patients were divided into spastic group (26 cases), normal muscle tone control group (15 cases). Modified Ashworth Scale (MAS) was applied in both groups for assessing muscle tone of lower limbs (no influence, contralateral). Muscle architectural parameters of ultrasound measurement include muscle thickness, fascicle length and pennation angle. The difference of three muscle architectural parameters between the affected side and the contralateral side in spastic group and the difference of MAS and three muscle architectural parameters between spastic group and normal control group were compared. RESULTS: MAS score, Pennation Angle (PA) and Muscular Thickness (MT) value of MAP in spastic group were significantly higher than the control group, Fascicle length (FL) is significantly lower than the control group (P < 0.05). In spastic group, MAS score, PA and MT value of MAP of affected side muscle was substantially higher than that of contralateral, FL value significantly lower than that of contralateral (P < 0.05). There was positive correlation between MAS and PA and MT but was negative correlation between MAS and FL, rank correlation coefficient test was statistical significant (p < 0.05). Logistic multivariate regression analysis showed that spasticity can lead PA and FL to change (p < 0.05), there is no clear correlation between MT and spasticity occurs (P > 0.05). CONCLUSION: MAP has a better sensitivity in evaluating muscle tone between spastic patients and non-spastic patients, and degrees of spasticity have a clear corresponding exponential relationship to MAP. Combing MAS and MAP can assess muscle tone more objectively and accurately because subtle changes can be observed by testing values of architecture parameters that compensating for the shortcomings of MAS in reliability and validity. Thus it is helpful for guiding clinical antispastic practice.

Application of nonlinear dynamics analysis in assessing unconsciousness: a preliminary study.

OBJECTIVES: To quantify the degree of unconsciousness with EEG nonlinear analysis and investigate the change of EEG nonlinear properties under different conditions. METHODS: Twenty-one subjects in persistent vegetative state (PVS), 16 in minimally conscious state (MCS) and 30 normal conscious subjects (control group) with brain trauma or stroke were involved in the study. EEG was recorded under three conditions: eyes closed, auditory stimuli and painful stimuli. EEG nonlinear indices such as Lempel-Ziv complexity (LZC), approximate entropy (ApEn) and cross-approximate entropy (cross-ApEn) were calculated for all the subjects. RESULTS: The PVS subjects had the lowest nonlinear indices followed by the MCS subjects and the control group had the highest. The PVS and MCS group had poorer response to auditory and painful stimuli than the control group. Under painful stimuli, nonlinear indices of subjects who recovered (REC) increased more significantly than non-REC subjects. CONCLUSIONS: With EEG nonlinear analysis, the degree of suppression for PVS and MCS could be quantified. The changes of brain function for unconscious subjects could be captured by EEG nonlinear analysis. SIGNIFICANCE: EEG nonlinear analysis could characterise the changes of brain function for unconscious state and might have some value in predicting prognosis of unconscious subjects.

Measuring interconnection of the residual cortical functional islands in persistent vegetative state and minimal conscious state with EEG nonlinear analysis.

OBJECTIVES: The aim of the study is to investigate the cortical response to painful and auditory stimuli for subjects in persistent vegetative state (PVS) and minimal conscious state (MCS), and measure the interconnection of the residual cortical functional islands with electroencephalographic (EEG) nonlinear dynamic analysis (NDA). METHODS: Thirty PVS subjects, 20 MCS subjects and 30 subjects in normal conscious state (NCS) were involved in the study. EEG was recorded under three conditions: eyes closed, auditory stimuli and painful stimuli. EEG nonlinear index of cross-approximate entropy (C-ApEn) was calculated for all subjects. RESULTS: Interconnection of local and distant cortical networks of patients in PVS was generally suppressed, and painful or auditory stimulation could hardly cause any activation of associative cortices. Instead, interconnection of local cortical networks of patients in MCS improved significantly. The only significant difference with the NCS existed in the unaffected distant cortical networks. CONCLUSIONS: Interconnection of local and distant cortical networks in MCS is superior to that of PVS. NDA could measure interconnection of the residual cortical functional islands with associative cortices in the unconscious patients. SIGNIFICANCE: NDA can characterise the interconnection of cortical networks for the unconscious state and provide some information of unconsciousness at the awareness level.