Cognitive function influences cognitive-motor interference during dual task walking in multiple sclerosis.

BACKGROUND: Both physical and cognitive impairments are common in people with multiple sclerosis (PwMS). Performing a cognitive task while walking (i.e., dual-task walking) can introduce cognitive-motor interference (CMI), resulting in changes in walking performance. The association between the levels of cognitive impairment and of CMI in MS remains unclear. OBJECTIVES: To examine the association between cognitive functioning and differences in walking performance arise between single- and dual-task walking. METHODS: Ninety-five PwMS performed self-preferred pace walking and dual-task walking. The gait parameters recorded were used to compute dual task costs (DTC) as a metric of CMI. Cognitive functioning was assessed using Match, an unsupervised test developed based on the Symbol Digit Modalities Test. Participants were categorized as higher (HCF) and lower cognitive functioning (LCF) based on a Match z-score < -1.5. RESULTS: LCF group had elevated DTC for stride velocity, relative to the HCF group. Higher DTC for stride velocity was associated with lower cognition, as assessed by Match test. CONCLUSION: The findings support the hypothesis that CMI is associated with cognitive functioning in PwMS.

Effects of transcranial alternating current stimulation on cognitive function in people with multiple sclerosis: A randomized controlled trial.

BACKGROUND: Cognitive impairment is a core symptom that profoundly impacts the lives of people with multiple sclerosis (PwMS). Since the existing disease modifying therapies can only stabilize, but not actively treat, cognition in PwMS, there is an unmet need to expand approaches to treat these cognitive symptoms. Transcranial alternating current stimulation (tACS) permits frequency-specific entrainment of neural oscillations intrinsic to cognitive activity. However, the effects of the tACS on cognitive function in PwMS have not yet been assessed. We aimed to evaluate the potential efficacy of applying frontal theta-tACS to improve information processing speed in PwMS. METHODS: 60 PwMS with cognitive complaints were enrolled in a double-blinded, randomized, controlled trial with three stimulation groups: 2 mA, 1 mA, or sham control. A single session of theta-tACS was applied while participants were engaged in a cognitive program which has shown to improve processing speed in PwMS. tACS effects were examined by the Symbol Digit Modalities Test (SDMT). Tolerability, side effects and acceptability were measured. RESULTS: 1 mA groups had a significantly higher SDMT score after stimulation compared to their pre-stimulation score, 2 mA group showed a marginally significant improvement of their SDMT score, while the SDMT score in the sham group did not change. Overall, 49% of the stimulation group participants showed a clinically meaningful SDMT improvement (4+-point increase). CONCLUSION: tACS is a well-tolerated, non-pharmacological intervention. Based on the positive effects observed in the current study of a single session of tACS applied during cognitive engagement, the effects of repeated tACS on cognitive function in PwMS merit further research. TRIAL REGISTRATION: ClinicalTrials.gov NCT04466228.

A virtual reality program to assess cognitive function in multiple sclerosis: A pilot study.

Introduction: Cognitive impairment is a debilitating symptom in people with multiple sclerosis (MS). Most of the neuropsychological tasks have little resemblance to everyday life. There is a need for ecologically valid tools for assessing cognition in real-life functional contexts in MS. One potential solution would involve the use of virtual reality (VR) to exert finer control over the task presentation environment; however, VR studies in the MS population are scarce. Objectives: To explore the utility and feasibility of a VR program for cognitive assessment in MS. Methods: A VR classroom embedded with a continuous performance task (CPT) was assessed in 10 non-MS adults and 10 people with MS with low cognitive functioning. Participants performed the CPT with distractors (i.e., WD) and without distractors (i.e., ND). The Symbol Digit Modalities Test (SDMT), California Verbal Learning Test-II (CVLT-II), and a feedback survey on the VR program was administered. Results: People with MS exhibited greater reaction time variability (RTV) compared to non-MS participants, and greater RTV in both WD and ND conditions was associated with lower SDMT. Conclusions: VR tools warrant further research to determine their value as an ecologically valid platform for assessing cognition and everyday functioning in people with MS.

Capturing cognitive changes in multiple sclerosis by performance-based functional and virtual reality assessments.

Cognitive impairment (CI) has been recognized as one of the core multiple sclerosis (MS) symptoms that profoundly impact lives of people with MS (PwMS). Clinical trials have begun to focus on cognition as a primary or secondary outcome, but translating improvements in cognitive testing scores to functioning in the real world is difficult. Performance-based functional assessments and virtual reality (VR) assessments, which incorporate real-world challenges, have been proposed as a way to better assess functional cognition (i.e., cognitive performance and its impact on real-life cognitive functioning of PwMS) and could address the difficulty in evaluating the impact of a treatment on real-world functioning. In this narrative review, we identify and summarize some of the promising recent research applications of performance-based functional assessments and VR tools to assess functional cognition in MS. Overall, most of the studies suggest that functional and VR assessments can detect cognitive differences between people with and without MS and between PwMS with and without CI. Furthermore, performance on some of the functional and VR assessments was associated with performance on standard cognitive assessments. However, developing any guidelines on how to implement these assessments in clinical practice is difficult because of the relatively small sample size across these studies. Performance-based functional and VR assessments represent an innovative approach to increasing sensitivity of how cognitive impairments/abilities present in the daily life of PwMS. More studies, with a larger sample size, robust research methods, and pre- and post-treatment assessments, are warranted to validate relevant, accessible functional and VR assessments before implementing these assessment approaches in clinical practice.

Leveraging technology to personalize cognitive enhancement methods in aging.

As population aging advances at an increasing rate, efforts to help people maintain or improve cognitive function late in life are critical. Although some studies have shown promise, the question of whether cognitive training is an effective tool for improving general cognitive ability remains incompletely explored, and study results to date have been inconsistent. Most approaches to cognitive enhancement in older adults have taken a 'one size fits all' tack, as opposed to tailoring interventions to the specific needs of individuals. In this Perspective, we argue that modern technology has the potential to enable large-scale trials of public health interventions to enhance cognition in older adults in a personalized manner. Technology-based cognitive interventions that rely on closed-loop systems can be tailored to individuals in real time and have the potential for global testing, extending their reach to large and diverse populations of older adults. We propose that the future of cognitive enhancement in older adults will rely on harnessing new technologies in scientifically informed ways.

Transitioning From S1P Receptor Modulators to B Cell-Depleting Therapies in Multiple Sclerosis: Clinical, Radiographic, and Laboratory Data.

BACKGROUND AND OBJECTIVES: Patients with multiple sclerosis (MS) transition from oral sphingosine-1-receptor (S1P) modulators to anti-CD20 therapies for several circumstances. Optimal timing of this transition is uncertain, given competing concerns of rebound disease activity and ensuring immune reconstitution. The objective of this study was to evaluate the relationship between inflammatory activity and the transition period from fingolimod to anti-CD20 therapies in a real-world MS cohort. METHODS: Medical records were reviewed for all patients at our center transitioning from fingolimod to rituximab or ocrelizumab between 2010 and October 2020. Time periods reviewed were the following: before fingolimod discontinuation, interval between fingolimod and anti-CD20 treatments, and after the first anti-CD20 infusion. The primary outcome was clinical relapses; MRI activity, time to absolute lymphocyte count (ALC) recovery, and infections were secondary. Clinical and demographic factors significant in univariable analyses were included in multivariable analyses. RESULTS: Transition data were available for 108 patients (68.5% women, 68.5% relapsing-remitting MS, mean age 44.6 years). The median (interquartile range) interval between fingolimod and anti-CD20 therapy was 28 (1-115.2) days. Six of 51 patients (11.8%) with intervals >1 month and 0/57 patients with shorter intervals experienced a relapse (MRI confirmed) within 6 months of fingolimod discontinuation. In the year following anti-CD20 initiation, 4/108 patients (3.7%) experienced a relapse (median 214.5 days after infusion). An additional 7% of those undergoing contrast-enhanced MRIs developed Gd+ lesions. ALC normalized following treatment switch in 89/92; the interval between treatments was unrelated to ALC recovery or infection. DISCUSSION: Delaying anti-CD20 start to monitor ALC after S1P modulator discontinuation may not be necessary and could increase rebound risk. ALC monitoring could instead occur after a rapid switch to anti-CD20 treatment.

Remote Assessments of Hand Function in Neurological Disorders: Systematic Review.

BACKGROUND: Loss of fine motor skills is observed in many neurological diseases, and remote monitoring assessments can aid in early diagnosis and intervention. Hand function can be regularly assessed to monitor loss of fine motor skills in people with central nervous system disorders; however, there are challenges to in-clinic assessments. Remotely assessing hand function could facilitate monitoring and supporting of early diagnosis and intervention when warranted. OBJECTIVE: Remote assessments can facilitate the tracking of limitations, aiding in early diagnosis and intervention. This study aims to systematically review existing evidence regarding the remote assessment of hand function in populations with chronic neurological dysfunction. METHODS: PubMed and MEDLINE, CINAHL, Web of Science, and Embase were searched for studies that reported remote assessment of hand function (ie, outside of traditional in-person clinical settings) in adults with chronic central nervous system disorders. We excluded studies that included participants with orthopedic upper limb dysfunction or used tools for intervention and treatment. We extracted data on the evaluated hand function domains, validity and reliability, feasibility, and stage of development. RESULTS: In total, 74 studies met the inclusion criteria for Parkinson disease (n=57, 77% studies), stroke (n=9, 12%), multiple sclerosis (n=6, 8%), spinal cord injury (n=1, 1%), and amyotrophic lateral sclerosis (n=1, 1%). Three assessment modalities were identified: external device (eg, wrist-worn accelerometer), smartphone or tablet, and telerehabilitation. The feasibility and overall participant acceptability were high. The most common hand function domains assessed included finger tapping speed (fine motor control and rigidity), hand tremor (pharmacological and rehabilitation efficacy), and finger dexterity (manipulation of small objects required for daily tasks) and handwriting (coordination). Although validity and reliability data were heterogeneous across studies, statistically significant correlations with traditional in-clinic metrics were most commonly reported for telerehabilitation and smartphone or tablet apps. The most readily implementable assessments were smartphone or tablet-based. CONCLUSIONS: The findings show that remote assessment of hand function is feasible in neurological disorders. Although varied, the assessments allow clinicians to objectively record performance in multiple hand function domains, improving the reliability of traditional in-clinic assessments. Remote assessments, particularly via telerehabilitation and smartphone- or tablet-based apps that align with in-clinic metrics, facilitate clinic to home transitions, have few barriers to implementation, and prompt remote identification and treatment of hand function impairments.

Assessing Cognitive Function in Multiple Sclerosis With Digital Tools: Observational Study.

BACKGROUND: Cognitive impairment (CI) is one of the most prevalent symptoms of multiple sclerosis (MS). However, it is difficult to include cognitive assessment as part of MS standard care since the comprehensive neuropsychological examinations are usually time-consuming and extensive. OBJECTIVE: To improve access to CI assessment, we evaluated the feasibility and potential assessment sensitivity of a tablet-based cognitive battery in patients with MS. METHODS: In total, 53 participants with MS (24 [45%] with CI and 29 [55%] without CI) and 24 non-MS participants were assessed with a tablet-based cognitive battery (Adaptive Cognitive Evaluation [ACE]) and standard cognitive measures, including the Symbol Digit Modalities Test (SDMT) and the Paced Auditory Serial Addition Test (PASAT). Associations between performance in ACE and the SDMT/PASAT were explored, with group comparisons to evaluate whether ACE modules can capture group-level differences. RESULTS: Correlations between performance in ACE and the SDMT (R=-0.57, P<.001), as well as PASAT (R=-0.39, P=.01), were observed. Compared to non-MS and non-CI MS groups, the CI MS group showed a slower reaction time (CI MS vs non-MS: P<.001; CI MS vs non-CI MS: P=.004) and a higher attention cost (CI MS vs non-MS: P=.02; CI MS vs non-CI MS: P<.001). CONCLUSIONS: These results provide preliminary evidence that ACE, a tablet-based cognitive assessment battery, provides modules that could potentially serve as a digital cognitive assessment for people with MS. TRIAL REGISTRATION: ClinicalTrials.gov NCT03569618; https://clinicaltrials.gov/ct2/show/NCT03569618.

Effects of melatonin on sleep disturbances in multiple sclerosis: A randomized, controlled pilot study.

BACKGROUND: Sleep disturbances are commonly reported by people with multiple sclerosis (PwMS). However, optimal management of sleep disturbances is uncertain, and objective studies of sleep quality in PwMS are scarce. OBJECTIVES: To determine the effect of exogenous melatonin on sleep quality and sleep disturbances in PwMS. METHODS: Thirty adult PwMS reporting sleep difficulties were recruited in a randomized, controlled, double-blind cross-over study. They took either melatonin or placebo for 2 weeks, and the opposite for the following 2 weeks. During weeks 2 and 4, an actigraph was used to capture mean total sleep time and sleep efficiency. Patient-reported outcomes (PROs) were collected at weeks 0, 2 and 4. RESULTS: Melatonin use significantly improved mean total sleep time (p = 0.03), with a trend towards higher sleep efficiency (p = 0.06). No PROs were significantly different; there was a trend for melatonin use to decrease mean Insomnia Severity Index score (p = 0.07), improve Pittsburgh Sleep Quality Index sleep quality component (p = 0.07), and improve NeuroQoL-Fatigue (p = 0.06). No other PROs showed differences between melatonin and placebo; nor did step count measured by actigraphy (all p > 0.45). CONCLUSION: These results provide preliminary evidence that melatonin, a low-cost, over-the-counter supplement, could improve objective measures of sleep quality in PwMS.

Individual differences in neuroanatomy and neurophysiology predict effects of transcranial alternating current stimulation.

BACKGROUND: Noninvasive transcranial electrical stimulation (tES) research has been plagued with inconsistent effects. Recent work has suggested neuroanatomical and neurophysiological variability may alter tES efficacy. However, direct evidence is limited. OBJECTIVE: We have previously replicated effects of transcranial alternating current stimulation (tACS) on improving multitasking ability in young adults. Here, we attempt to assess whether these stimulation parameters have comparable effects in older adults (aged 60-80 years), which is a population known to have greater variability in neuroanatomy and neurophysiology. It is hypothesized that this variability in neuroanatomy and neurophysiology will be predictive of tACS efficacy. METHODS: We conducted a pre-registered study where tACS was applied above the prefrontal cortex (between electrodes F3-F4) while participants were engaged in multitasking. Participants were randomized to receive either 6-Hz (theta) tACS for 26.67 min daily for three days (80 min total; Long Exposure Theta group), 6-Hz tACS for 5.33 min daily (16-min total; Short Exposure Theta group), or 1-Hz tACS for 26.67 min (80 min total; Control group). To account for neuroanatomy, magnetic resonance imaging data was used to form individualized models of the tACS-induced electric field (EF) within the brain. To account for neurophysiology, electroencephalography data was used to identify individual peak theta frequency. RESULTS: Results indicated that only in the Long Theta group, performance change was correlated with modeled EF and peak theta frequency. Together, modeled EF and peak theta frequency accounted for 54%-65% of the variance in tACS-related performance improvements, which sustained for a month. CONCLUSION: These results demonstrate the importance of individual differences in neuroanatomy and neurophysiology in tACS research and help account for inconsistent effects across studies.

Effects of Transcranial Direct Current Stimulation on Cognition, Mood, Pain, and Fatigue in Multiple Sclerosis: A Systematic Review and Meta-Analysis.

Background: The study aimed to evaluate the effects of transcranial direct current stimulation (tDCS) on cognition, mood disturbance, pain, and fatigue in people with multiple sclerosis (PwMS). Methods: A literature search was performed on articles published between January 1990 and May 2020 in Pubmed, Medline, and Web of Science using the following keywords and their abbreviation in combinations: multiple sclerosis and transcranial direct current stimulation. Mean effect size (ES) and 95% confidence interval were calculated for each domain of interest. Results: Seventeen articles with a total of 383 PwMS were included in this analysis. For cognition, a strong effect size was found for the trial administering the Symbol Digit Modalities Test (ES: 1.15), whereas trials applying the Attention Network Test showed a negative effect size of -0.49. Moderate to strong effect sizes were observed for mood disturbance (mean ES: 0.92), pain (mean ES: 0.59), and fatigue (mean ES: 0.60). Further subgroup analyses for MS-related fatigue showed that both high and low intensities of stimulation lead to nearly the same degree of favorable effects. More pronounced effects were observed in studies administering the Fatigue Severity Scale compared with studies using other fatigue measures such as the Modified Fatigue Impact Scale. Conclusion: These results provide preliminary evidence that tDCS has a favorable effect on cognitive processing speed, mood disturbance, pain, and fatigue in MS. However, the effects on cognition and fatigue vary based on the specific assessment used.

Expanded access to multiple sclerosis teleneurology care following the COVID-19 pandemic.

BACKGROUND: Teleneurology for multiple sclerosis (MS) care was considered feasible, but utilization was limited. OBJECTIVE: To describe how the existing teleneurology populations at two academic MS Centers changed during the COVID-19 pandemic. METHODS: In this cross-sectional study, we captured all in-person and teleneurology visits at two academic MS Centers between January 2019 and April 2020. We compared group differences between the Centers, and COVID-related changes using T-, chi-squared Kruskal-Wallis and Fisher exact tests. RESULTS: 2268 patients completed 2579 teleneurology visits (mean age 48.3 ± 13.3 years, 72.9% female). Pre-COVID, the Centers' teleneurology populations were similar for age, sex, MS type, and disability level (all p > 0.1), but differed for race (96.5% vs 80.7% white, p ≤ 0.001), MS treatment (49.1% vs 32.1% infusible, p ≤ 0.001), and median distance from Center (72 vs 186 miles, p ≤ 0.001). Post-COVID, both Centers' teleneurology populations had more black (12.7% vs 4.37%, p ≤ 0.001) and local (median 34.5 vs 102 miles, p ≤ 0.001) patients. CONCLUSION: Teleneurology visits in 2019 reflected the organizational and local teleneurology reimbursement patterns of our Centers. Our post-COVID-19 changes illustrate the potential for payors and policy to change disparities in access to, or utilization of, remote care. Patients' perception of care quality and value following this shift warrants study.

Correction: Application of an Adaptive, Digital, Game-Based Approach for Cognitive Assessment in Multiple Sclerosis: Observational Study.

[This corrects the article DOI: 10.2196/24356.].

Application of an Adaptive, Digital, Game-Based Approach for Cognitive Assessment in Multiple Sclerosis: Observational Study.

BACKGROUND: Cognitive impairment is one of the most debilitating manifestations of multiple sclerosis. Currently, the assessment of cognition relies on a time-consuming and extensive neuropsychological examination, which is only available in some centers. OBJECTIVE: To enable simpler, more accessible cognitive screening, we sought to determine the feasibility and potential assessment sensitivity of an unsupervised, adaptive, video game-based digital therapeutic to assess cognition in multiple sclerosis. METHODS: A total of 100 people with multiple sclerosis (33 with cognitive impairment and 67 without cognitive impairment) and 24 adults without multiple sclerosis were tested with the tablet game (EVO Monitor) and standard measures, including the Brief International Cognitive Assessment for Multiple Sclerosis (which included the Symbol Digit Modalities Test [SDMT]) and Multiple Sclerosis Functional Composite 4 (which included the Timed 25-Foot Walk test). Patients with multiple sclerosis also underwent neurological evaluations and contributed recent structural magnetic resonance imaging scans. Group differences in EVO Monitor performance and the association between EVO Monitor performance and standard measures were investigated. RESULTS: Participants with multiple sclerosis and cognitive impairment showed worse performance in EVO Monitor compared with participants without multiple sclerosis (P=.01) and participants with multiple sclerosis without cognitive impairment (all P<.002). Regression analyses indicated that participants with a lower SDMT score showed lower performance in EVO Monitor (r=0.52, P<.001). Further exploratory analyses revealed associations between performance in EVO Monitor and walking speed (r=-0.45, P<.001) as well as brain volumetric data (left thalamic volume: r=0.47, P<.001; right thalamic volume: r=0.39, P=.002; left rostral middle frontal volume: r=0.28, P=.03; right rostral middle frontal volume: r=0.27, P=.03). CONCLUSIONS: These findings suggest that EVO Monitor, an unsupervised, video game-based digital program integrated with adaptive mechanics, is a clinically valuable approach to measuring cognitive performance in patients with multiple sclerosis. TRIAL REGISTRATION: ClinicalTrials.gov NCT03569618; https://clinicaltrials.gov/ct2/show/NCT03569618.

An electronic, unsupervised patient-reported Expanded Disability Status Scale for multiple sclerosis.

BACKGROUND: In persons with multiple sclerosis (MS), the Expanded Disability Status Scale (EDSS) is the criterion standard for assessing disability, but its in-person nature constrains patient participation in research and clinical assessments. OBJECTIVE: The aim of this study was to develop and validate a scalable, electronic, unsupervised patient-reported EDSS (ePR-EDSS) that would capture MS-related disability across the spectrum of severity. METHODS: We enrolled 136 adult MS patients, split into a preliminary testing Cohort 1 (n = 50), and a validation Cohort 2 (n = 86), which was evenly distributed across EDSS groups. Each patient completed an ePR-EDSS either immediately before or after a MS clinician's Neurostatus EDSS evaluation. RESULTS: In Cohort 2, mean age was 50.6 years (range = 26-80) and median EDSS was 3.5 (interquartile range (IQR) = [1.5, 5.5]). The ePR-EDSS and EDSS agreed within 1-point for 86% of examinations; kappa for agreement within 1-point was 0.85 (p < 0.001). The correlation coefficient between the two measures was 0.91 (<0.001). DISCUSSION: The ePR-EDSS was highly correlated with EDSS, with good agreement even at lower EDSS levels. For clinical care, the ePR-EDSS could enable the longitudinal monitoring of a patient's disability. For research, it provides a valid and rapid measure across the entire spectrum of disability and permits broader participation with fewer in-person assessments.

Multimodal sensory integration: Diminishing returns in rhythmic synchronization.

Synchronizing movements with events in the surrounding environment is a ubiquitous aspect of behavior. Experiments studying multimodal integration and rhythmic synchronization tend to focus on how bimodal (e.g., audio-visual) stimuli enhances synchronization performance (i.e., reduced variability) compared with synchronization with its unimodal constituents. As such, it is unclear whether trimodal (i.e., audio-visual-tactile) stimuli may yield additional performance benefits. To address this, we developed a multimodal sensorimotor synchronization assessment that incorporates audio, visual, and vibrotactile stimuli. Results replicate performance improvements with bimodal compared with unimodal stimuli. However, trimodal stimuli yields less, or in some cases no advantage compared with bimodal stimuli. These results demonstrate that in this case, increasing the amount of sensory information beyond bimodal stimuli yields little or no additional performance benefits. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Attenuated NoGo-related beta desynchronisation and synchronisation in Parkinson's disease revealed by magnetoencephalographic recording.

Parkinson's disease (PD) is a neurodegenerative disorder characterised by motor abnormalities. Many non-demented patients with PD have cognitive impairment especially in executive functions. Using magnetoencephalographic (MEG) recording combined with event-related desynchronisation/synchronisation (ERD/ERS) analysis, we investigated cortical executive functions during a Go/NoGo task in PD patients and matched healthy subjects. PD patients had a longer reaction time in the Go condition and had a higher error ratio in both Go and NoGo conditions. The MEG analysis showed that the PD patients had a significant reduction in beta ERD during the NoGo condition and in beta ERS during both Go and NoGo conditions compared with the healthy subjects (all p < 0.05). Moreover, in the Go condition, the onsets of beta ERD and ERS were delayed in PD patients. Notably, NoGo ERS was negatively correlated with the Unified Parkinson's Disease Rating Scale (UPDRS) score in PD patients. The present study demonstrated abnormalities in motor programming, response inhibition, and frontal inhibitory modulation in PD. Further extensive investigations are necessary to confirm the longitudinal treatment responses in PD.

Parametric effects of transcranial alternating current stimulation on multitasking performance.

BACKGROUND: We have previously demonstrated that transcranial alternating current stimulation (tACS) can generate positive effects on multitasking performance and associated neurophysiological measures when it is applied with anti-phase theta band stimulation across bilateral prefrontal cortex (PFC) and a short (1-min) inter-session interval (ISI). However, it is unclear how altering the phase of stimulation and the duration of the ISI might impact positive tACS effects. Here, we investigated the role of tACS parameters in engendering performance improvements by manipulating these two stimulation parameters (i.e. phase and ISI) in two experiments. METHODS: Repetitive sessions of bilateral PFC theta-tACS were applied with in-phase stimulation + 1-min ISI (experiment 1) and anti-phase stimulation + 5-min ISI (experiment 2) while participants were engaged in a multitasking challenge accompanied by electroencephalography (EEG) data collection. RESULTS: Compared to the control group, in-phase stimulation + 1-min ISI showed an enhancement of multitasking performance coupled with a modulation of posterior alpha (8-12 Hz) and beta (13-30 Hz) activities. However, repetitive sessions of anti-phase tACS + 5-min ISI did not generate significant enhancement in multitasking performance, nor changes in neural oscillatory activities compared to the control group. CONCLUSION: The results revealed that the previous reported positive tACS effects on multitasking performance are not affected by manipulating the phase of current polarity. Yet, changing the ISI of the stimulation protocol eliminated the previous observed performance improvements. Taken together, these results stress the importance of stimulation protocol for generating positive tACS effects on cognitive function and neural oscillations.

Enhancement of multitasking performance and neural oscillations by transcranial alternating current stimulation.

Multitasking is associated with the generation of stimulus-locked theta (4-7 Hz) oscillations arising from prefrontal cortex (PFC). Transcranial alternating current stimulation (tACS) is a non-invasive brain stimulation technique that influences endogenous brain oscillations. Here, we investigate whether applying alternating current stimulation within the theta frequency band would affect multitasking performance, and explore tACS effects on neurophysiological measures. Brief runs of bilateral PFC theta-tACS were applied while participants were engaged in a multitasking paradigm accompanied by electroencephalography (EEG) data collection. Unlike an active control group, a tACS stimulation group showed enhancement of multitasking performance after a 90-minute session (F1,35 = 6.63, p = 0.01, ηp2 = 0.16; effect size = 0.96), coupled with significant modulation of posterior beta (13-30 Hz) activities (F1,32 = 7.66, p = 0.009, ηp2 = 0.19; effect size = 0.96). Across participant regression analyses indicated that those participants with greater increases in frontal theta, alpha and beta oscillations exhibited greater multitasking performance improvements. These results indicate frontal theta-tACS generates benefits on multitasking performance accompanied by widespread neuronal oscillatory changes, and suggests that future tACS studies with extended treatments are worth exploring as promising tools for cognitive enhancement.

Abnormal Somatosensory Synchronization in Patients With Paroxysmal Kinesigenic Dyskinesia: A Magnetoencephalographic Study.

Paroxysmal kinesigenic dyskinesia (PKD) is a rare group of hyperkinetic movement disorders characterized by brief attacks of choreoathetosis or dystonia. To clarify the alterations of the functional connectivity within the somatosensory network in PKD patients, magnetoencephalographic (MEG) responses to paired median-nerve electrical stimulation were recorded in 10 PKD patients treated by carbamazepine or oxcarbamazepine and 22 age-matched controls. In patients, MEG recordings were obtained during drug-on and -off periods. Source-based functional connectivity analysis was performed between contralateral primary (cSI) and secondary (cSII), and ipsilateral secondary (iSII) somatosensory areas. During drug-off periods, patients with PKD demonstrated decreased cSI-iSII and increased cSII-iSII somatosensory connectivity at theta band. Drug-on periods lowered the functional connectivity in cSI-cSII at alpha and beta bands and in cSII-iSII at theta band compared with the drug-off periods. We suggest that altered theta functional connectivity in cSI-iSII and cSII-iSII could be the neurophysiological signatures in PKD.