Sequential Finger Tapping Task Research Articles

Age-related differences in finger interdependence during complex hand movements.

The well-known decrease in finger dexterity during healthy aging leads to a significant reduction in quality of life. Still, the exact patterns of altered finger kinematics of older adults in daily life are fairly unexplored. Finger interdependence is the unintentional comovement of fingers that are not intended to move, and it is known to vary across the lifespan. Nevertheless, the magnitude and direction of age-related differences in finger interdependence are ambiguous across studies and tasks and have not been explored in the context of daily life finger movements. We investigated five different free and daily-life-inspired finger movements of the right, dominant hand as well as a sequential finger tapping task of the thumb against the other fingers, in 17 younger (22-37 yr) and 17 older (62-80 yr) adults using an exoskeleton data glove for data recording. Using inferential statistics, we found that the unintentional comovement of fingers generally decreases with age in all performed daily-life-inspired movements. Finger tapping, however, showed a trend towards higher finger interdependence for older compared with younger adults. Using machine learning, we predicted the age group of a person from finger interdependence features of single movement trials significantly better than chance level for the daily-life-inspired movements, but not for finger tapping. Taken together, we show that for specific tasks, decreased finger interdependence (i.e., less comovement) could potentially act as a marker of human aging that specifically characterizes older adults' complex finger movements in daily life.NEW & NOTEWORTHY Kinematic finger movement data were analyzed with regard to age-related differences. Extensive analyses of complex and daily-life-inspired movements reveal that the direction of age effects is not uniform but task-dependent: Although older adults generally show more finger interdependence than younger adults in a simple finger tapping task, this effect is reversed for daily-life-inspired movement tasks. For these tasks, finger interdependence indices offer potential new markers to predict the age group of an individual using machine learning approaches.

Alterations in learning-related cortical activation and functional connectivity by high-definition transcranial direct current stimulation after stroke: an fNIRS study.

Motor learning is a key component of stroke neurorehabilitation. High-definition transcranial direct current stimulation (HD-tDCS) was recently developed as a tDCS technique that increases the accuracy of current delivery to the brain using arrays of small electrodes. The purpose of this study was to investigate whether HD-tDCS alters learning-related cortical activation and functional connectivity in stroke patients using functional near-infrared spectroscopy (fNIRS). Using a sham-controlled crossover study design, 16 chronic stroke patients were randomly assigned to one of two intervention conditions. Both groups performed the sequential finger tapping task (SFTT) on five consecutive days, either with (a) real HD-tDCS or (b) with sham HD-tDCS. HD-tDCS (1 mA for 20 min, 4 × 1) was administered to C3 or C4 (according to lesion side). fNIRS signals were measured during the SFTT with the affected hand before (baseline) and after each intervention using fNIRS measurement system. Cortical activation and functional connectivity of NIRS signals were analyzed using a statistical parametric mapping open-source software package (NIRS-SPM), OptoNet II®. In the real HD-tDCS condition, oxyHb concentration increased significantly in the ipsilesional primary motor cortex (M1). Connectivity between the ipsilesional M1 and the premotor cortex (PM) was noticeably strengthened after real HD-tDCS compared with baseline. Motor performance also significantly improved, as shown in response time during the SFTT. In the sham HD-tDCS condition, functional connectivity between contralesional M1 and sensory cortex was enhanced compared with baseline. There was tendency toward improvement in SFTT response time, but without significance. The results of this study indicated that HD-tDCS could modulate learning-related cortical activity and functional connectivity within motor networks to enhance motor learning performance. HD-tDCS can be used as an additional tool for enhancing motor learning during hand rehabilitation for chronic stroke patients.

Sustained effect of auditory entrainment on sequential tapping: The role of movement path complexity

The effects of auditory-motor entrainment have generally been investigated with periodic movements. Previous research has focused on how auditory-motor entrainment is influenced by the temporal structure of rhythms. The present study aimed to investigate whether auditory entrainment improved timing performance of sequential movements with varied path structures, and whether path complexity would affect any possible sustained effect of auditory entrainment. We also investigated whether the sustained effect was moderated by hearing single- vs. multiple-pitch audio prompts. Thirty participants were enrolled to perform a sequential finger-tapping task with discrete targets, in which the algebraic ratio relation of path lengths was manipulated as path complexity. Participants completed three stages per trial: initiation (to introduce the path sequence), entrainment (tapping along with the auditory and visual cues), and timekeeping (repeating the sequence without cues). We found timing improvement in terms of mean asynchronies and absolute interval error decrease after auditory entrainment. Only interval accuracy performance during timekeeping and entrainment was affected by path complexity. Moreover, no clear difference was observed between the rhythm sets in terms of single vs. multiple pitches. In conclusion, we found that phase and interval duration accuracy of predefined isochronous sequential movements with varied path complexity can be improved by auditory entrainment, and that auditory entrainment affects our performance beyond the actual presence of the auditory cue.

Breaking the barriers to designing online experiments: A novel open-source platform for supporting procedural skill learning experiments

BackgroundMotor learning experiments are typically performed in laboratory environments, which can be time-consuming and require dedicated equipment/personnel, thus limiting the ability to gather data from large samples. To address this problem, some researchers have transitioned to unsupervised online experiments, showing advantages in participant recruitment without losing validity. However, most online platforms require coding experience or time-consuming setups to create and run experiments, limiting their usage across the field. MethodTo tackle this issue, an open-source web-based platform was developed (https://experiments.neurro-lab.engin.umich.edu/) to create, run, and manage procedural skill learning experiments without coding or setup requirements. The feasibility of the platform and the comparability of the results between supervised (n = 17) and unsupervised (n = 24) were tested in 41 naive right-handed participants using an established sequential finger tapping task. The study also tested if a previously reported rapid form of offline consolidation (i.e., microscale learning) in procedural skill learning could be replicated with the developed platform and evaluated the extent of interlimb transfer associated with the finger tapping task. ResultsThe results indicated that the performance metrics were comparable between the supervised and unsupervised groups (all p's > 0.05). The learning curves, mean tapping speeds, and micro-scale learning were similar to previous studies. Training led to significant improvements in mean tapping speed (2.22 ± 1.48 keypresses/s, p < 0.001) and a significant interlimb transfer of learning (1.22 ± 1.43 keypresses/s, p < 0.05). ConclusionsThe results show that the presented platform may serve as a valuable tool for conducting online procedural skill-learning experiments.

Anodal tDCS does not enhance the learning of the sequential finger-tapping task by motor imagery practice in healthy older adults.

Motor imagery practice (MIP) and anodal transcranial direct current stimulation (a-tDCS) are innovative methods with independent positive influence on motor sequence learning (MSL) in older adults. The present study investigated the effect of MIP combined with a-tDCS over the primary motor cortex (M1) on the learning of a finger tapping sequence of the non-dominant hand in healthy older adults. Thirty participants participated in this double-blind sham-controlled study. They performed three MIP sessions, one session per day over three consecutive days and a retention test 1 week after the last training session. During training / MIP, participants had to mentally rehearse an 8-element finger tapping sequence with their left hand, concomitantly to either real (a-tDCS group) or sham stimulation (sham-tDCS group). Before and after MIP, as well as during the retention test, participants had to physically perform the same sequence as fast and accurately as possible. Our main results showed that both groups (i) improved their performance during the first two training sessions, reflecting acquisition/on-line performance gains, (ii) stabilized their performance from one training day to another, reflecting off-line consolidation; as well as after 7 days without practice, reflecting retention, (iii) for all stages of MSL, there was no significant difference between the sham-tDCS and a-tDCS groups. This study highlights the usefulness of MIP in motor sequence learning for older adults. However, 1.5 mA a-tDCS did not enhance the beneficial effects of MIP, which adds to the inconsistency of results found in tDCS studies. Future work is needed to further explore the best conditions of use of tDCS to improve motor sequence learning with MIP.

Effects of a brief afternoon nap on declarative and procedural memory

The relationship between sleep and memory consolidation has not been fully revealed. The current study aimed to investigate how a brief afternoon nap contributed to the consolidation of declarative and procedural memory by exploring the relationship between sleep characteristics (i.e., the durations of sleep stages and slow oscillation, slow-wave activity, and spindle activity extracted from sleep) and task performance and the relationship between delta, theta, alpha, and beta bands extracted from wake during task performance and task performance. Twenty-three healthy young adults underwent a paired associates learning task and a sequential finger-tapping task with easy and difficult levels and were tested for memory performance before and after the intervention (i.e., an about 30-min nap or stay awake). Electroencephalogram (EEG) signals were continously recorded during the whole experiment. Results revealed that a short afternoon nap improved movement speed for the procedural memory task, regardless of the task difficulty, but unaffected the performance on the declarative memory task. Besides, the improvement in movement speed for the easy procedural memory task was positively correlated with slow-wave activity (SWA) during non-rapid-eye-movement (NREM) sleep but negatively correlated with slow oscillation and spindle activity during sleep stage 2 and NREM sleep, and the improvement in the difficult procedural memory task correlated positively with SWA during NREM sleep. Moreover, performance on the easy declarative and procedural memory tasks was negatively correlated with the relative power of alpha or theta; whereas the alpha band was positively correlated with the difficult declarative memory performance. These findings suggested that a brief afternoon nap with NREM sleep would benefit procedural memory consolidation but not declarative memory; such contribution of napping to memory consolidation would be either explained by the sleep characteristics or physiological arousal during performing tasks; task difficulty would moderate the relationship between the declarative memory performance and EEGs during task performance.

Mental practice modulates functional connectivity between the cerebellum and the primary motor cortex

SummaryOur brain has the extraordinary capacity to improve motor skills through mental practice. Conceptually, this ability is attributed to internal forward models, which are cerebellar neural networks that can predict the sensory consequences of motor commands. In our study, we employed single and dual-coil transcranial magnetic stimulations to probe the level of corticospinal excitability and cerebellar-brain inhibition, respectively, before and after a mental practice session or a control session. Motor skill (i.e., accuracy and speed) was measured using a sequential finger tapping-task. We found that mental practice enhanced both speed and accuracy. In parallel, the functional connectivity between the cerebellum and the primary motor cortex changed, with less inhibition from the first to the second. These findings reveal the existence of neuroplastic changes within the cerebellum, supporting the involvement of internal models after mental practice.

Dorsolateral prefrontal cortex mediates working memory processes in motor skill learning

Neuroimaging studies have shown that the dorsolateral prefrontal cortex (DLPFC) is recruited during motor skill learning, which suggests the involvement of the DLPFC in working memory (WM) processes, such as selection and integration of motor representations temporarily stored in WM. However, direct evidence linking activation of the DLPFC to WM storage and manipulation during motor skill learning in real-time is rare. In this study, we conducted two experiments to investigate the causal role of DLPFC activity in WM storage and manipulation during motor skill learning under low and high WM-demand conditions. Participants received continuous theta burst stimulation (cTBS) and sham stimulation (crossover design) over the left DLPFC (experiment 1) or right DLPFC (experiment 2). Before and after stimulation, participants in both experiments performed a sequential finger-tapping (SFT) task containing repeated sequence (low-WM demand) and non-repeated sequence (high-WM demand) conditions which are used to study WM processes. The number of correct sequences (NoCS) and reproduction error rate were analyzed. Learning gains in NoCS improved significantly with the practice for both sequence types in the presence of either stimulation type. Compared to sham stimulation, cTBS over the left DLPFC resulted in significantly reduced learning gains in NoCS for non-repeated sequences. These results suggest that the left DLPFC contributes to WM manipulation during motor skill learning.

Functional Neural Networks in Writer's Cramp as Determined by Graph-Theoretical Analysis.

Dystonia, a debilitating neurological movement disorder, is characterized by involuntary muscle contractions and develops from a complex pathophysiology. Graph theoretical analysis approaches have been employed to investigate functional network changes in patients with different forms of dystonia. In this study, we aimed to characterize the abnormal brain connectivity underlying writer's cramp, a focal hand dystonia. To this end, we examined functional magnetic resonance scans of 20 writer's cramp patients (11 females/nine males) and 26 healthy controls (10 females/16 males) performing a sequential finger tapping task with their non-dominant (and for patients non-dystonic) hand. Functional connectivity matrices were used to determine group averaged brain networks. Our data suggest that in their neuronal network writer's cramp patients recruited fewer regions that were functionally more segregated. However, this did not impair the network's efficiency for information transfer. A hub analysis revealed alterations in communication patterns of the primary motor cortex, the thalamus and the cerebellum. As we did not observe any differences in motor outcome between groups, we assume that these network changes constitute compensatory rerouting within the patient network. In a secondary analysis, we compared patients with simple writer's cramp (only affecting the hand while writing) and those with complex writer's cramp (affecting the hand also during other fine motor tasks). We found abnormal cerebellar connectivity in the simple writer's cramp group, which was less prominent in complex writer's cramp. Our preliminary findings suggest that longitudinal research concerning cerebellar connectivity during WC progression could provide insight on early compensatory mechanisms in WC.

No Impact of Cerebellar Anodal Transcranial Direct Current Stimulation at Three Different Timings on Motor Learning in a Sequential Finger-Tapping Task.

Background: Recently, attention has grown toward cerebellar neuromodulation in motor learning using transcranial direct current stimulation (tDCS). An important point of discussion regarding this modulation is the optimal timing of tDCS, as this parameter could significantly influence the outcome. Hence, this study aimed to investigate the effects of the timing of cerebellar anodal tDCS (ca-tDCS) on motor learning using a sequential finger-tapping task (FTT).Methods: One hundred and twenty two healthy young, right-handed subjects (96 females) were randomized into four groups (Duringsham, Before, Duringreal, After). They performed 2 days of FTT with their non-dominant hand on a custom keyboard. The task consisted of 40 s of typing followed by 20 s rest. Each participant received ca-tDCS (2 mA, sponge electrodes of 25 cm2, 20 min) at the appropriate timing and performed 20 trials on the first day (T1, 20 min). On the following day, only 10 trials of FTT were performed without tDCS (T2, 10 min). Motor skill performance and retention were assessed.Results: All participants showed a time-dependent increase in learning. Motor performance was not different between groups at the end of T1 (p = 0.59). ca-tDCS did not facilitate the retention of the motor skill in the FTT at T2 (p = 0.27). Thus, our findings indicate an absence of the effect of ca-tDCS on motor performance or retention of the FTT independently from the timing of stimulation.Conclusion: The present results suggest that the outcome of ca-tDCS is highly dependent on the task and stimulation parameters. Future studies need to establish a clear basis for the successful and reproducible clinical application of ca-tDCS.

Neuromodulation of premotor and posterior parietal cortices for enhancing explicit motor sequence learning in healthy individuals: a randomized, sham-controlled crossover trial

Background: Anodal transcranial Direct Current Stimulation (tDCS) has been shown to be effective in improving human motor learning when applied over the contralateral primary motor cortex (M1). However, the stimulation of other cortical areas, such as the posterior parietal (PPC) and premotor (PMC) cortices, may be also beneficial. Methods: The present study (crossover design) investigated the effects of tDCS applied over PPC, PMC, and M1 on the acquisition and retention of a new motor skill, and on the generalization of such learned skill in healthy individuals. During a sequential finger-tapping task (FTT), performed with the non-dominant (left) hand, participants received real or sham anodal tDCS (1.5 mA, 20 min) over PPC, PMC, and the M1 of the right hemisphere. Explicit motor sequence learning was measured online (during the training with tDCS; primary outcome) and 24 hours after tDCS (retention, secondary outcome). A new, untrained, sequence was used to assess generalization effects (secondary outcome). Results: Anodal tDCS of M1 improved both online learning and retention. PMC tDCS facilitated the generalization of the learning effect to the untrained motor sequence. In contrast, neuromodulation of the PPC does not influence motor sequence learning. Conclusions: These findings show that, in addition to M1, higher-order associative cortical regions (PMC and PPC) are involved in explicit online motor sequence learning, retention and generalization playing different roles, as indicated by the differential modulatory effects of anodal tDCS.

Motor learning in unilateral cerebral palsy and the influence of corticospinal tract reorganization.

Cerebral Palsy (CP) is a complex neurological disorder, characterized by congenital motor disability associated with behaviour, perception and cognition disorders. The sensorimotor impairments represent the main hallmark of the disease, significantly impacting the quality of life. So far, few studies have investigated motor learning abilities in CP and their association with the plastic reorganization of the motor system remains largely unknown. The present proof-of-principle study explored explicit motor sequence learning in children with unilateral CP and different patterns of motor system reorganization (bilateral, ipsilateral, contralateral). Children with unilateral CP, and a group of age-matched typically developing (TD) children, underwent a sequential finger tapping task, performed with the affected hand by children with CP and with the non-dominant hand by TD children. The pattern of corticospinal tract projections in hemiparetic patients was assessed by single-pulse Transcranial Magnetic Stimulation (TMS). Results showed the presence of finger dexterity impairments in children with unilateral CP presenting with a bilateral or an ipsilateral control of the affected (trained) hand, as compared to TD children. Conversely, motor sequence learning was impaired in unilateral CP with ipsilateral or contralateral corticospinal reorganization, but not in the case of a bilateral control of the paretic hand. These preliminary findings, although referred to small clinical samples, suggest that unilateral control of the paretic upper-limb, from the ipsilateral or the contralateral motor cortex, may not be sufficient to develop typical motor learning with the affected hand, which seems to require a bilateral representation in the motor cortex. This evidence has potential implications for fine motor skills rehabilitation in CP.

Cued Memory Reactivation during Motor Imagery Practice Influences Early Improvement of Procedural Skill Learning

Reactivation processes are fundamental for procedural memory improvement. Targeted memory reactivation (TMR) influences memory consolidation through the re-exposure to certain perceptual components present in a previous phase of associative learning. On the other hand, motor imagery (MI) affects procedural skills through a repeated mental simulation of a pre-learned movement without physically moving. Both for TMR and MI, performance improvement has proven to be associated with an induction of reactivation processes. The positive effect of TMR is widely acknowledged in sleep. Here, we measured its impact on procedural learning during waking, in particular during MI practice, in line with the hypothesis that the exogenously induced involuntary reactivations through TMR could add up to the endogenous and voluntary reactivations induced by MI. Therefore, we assessed the influence on performance on a sequential finger tapping task of an auditory TMR during MI practice. It was compared to four conditions: (i) MI alone, (ii) MI during an incompatible sound stimulation, (iii) a mere video viewing and (iv) an auditory TMR during a video viewing. Results showed that the TMR + MI condition determined the largest early performance improvement as indexed by the combined measure of speed and accuracy (number of correct sequences typed in the task). We propose that TMR may enhance the effectiveness of MI protocols, and that MI could represent an optimal time window during wakefulness to take advantage of the effects of TMR.

Sleep and motor sequence learning consolidation in former iron deficient anemic adolescents

BackgroundIron deficiency is the most prevalent micronutrient deficiency worldwide. There is evidence that iron deficiency produces alterations in the developing brain, eventually leading to long-lasting effects on various cognitive functions. MethodsHere, we investigated motor learning and its consolidation after sleep in adolescents who sustained iron deficiency anemia (IDA) in infancy, compared to healthy controls, in the context of a long-term follow-up Chilean research project. Fifty-three adolescents who formerly had iron deficiency anemia as infants and 40 control adolescents practiced a sequential motor finger tapping task, before and after a night of sleep. Performance was measured at the end of learning, 30 min later (boost effect), and the next morning. ResultsRevealed slower learning in subjects with infant iron deficiency anemia than control subjects, followed by a proportionally similar performance boost at 30 min. Performance remained stable overnight in healthy controls but further improved in infant IDA adolescents, suggesting a beneficial effect of post-training sleep on the consolidation of incompletely learned motor skills. In particular, overnight gains in performance were observed in female, but not male infant iron deficiency anemic subjects, suggesting a gender effect. ConclusionsOur results indicate long-lasting motor learning deficits in infant IDA adolescents and provide support to the hypothesis that post-training sleep might, to some extent, compensate for hampered motor learning during wakefulness.

The motor engram as a dynamic change of the cortical network during early sequence learning: An fMRI study

Neural substrates of motor engrams in the human brain are hard to identify because their dormant states are difficult to discriminate. We utilized eigenvector centrality (EC) to measure the network information that accumulates as an engram during learning. To discriminate engrams formed by emphasis on speed or accuracy, we conducted functional MRI on 58 normal volunteers as they performed a sequential finger-tapping task with the non-dominant left hand. Participants alternated between performing a tapping sequence as quickly as possible (maximum mode) or at a constant speed of 2 Hz, paced by a sequence-specifying visual cue (constant mode). We depicted the formation of the motor engram by characterizing the dormant state as the increase in EC of the resting epoch throughout the training course, and the ecphory, or activated state, as the increment in EC during the task epoch relative to the alternated resting epoch. We found that a network covering the left anterior intraparietal sulcus and inferior parietal lobule represented the engram for the speed of execution, whereas bilateral premotor cortex and right primary motor cortex represented the sequential order of movements. This constitutes the first demonstration of learning-mode specific motor engrams formed by only 30 min of training.

Vividness and accuracy: Two independent aspects of motor imagery

Motor imagery is the mental execution of an action without any actual movement. Although numerous studies have utilized questionnaires to evaluate the vividness of motor imagery, it remains unclear whether it is related to the accuracy of motor imagery. To examine the relationship between vividness and accuracy, we investigated brain activity during kinesthetic and visual motor imagery, by using a novel sequential finger-tapping task. We estimated accuracy by measuring the fidelity of the actual performance and evaluated vividness by using a visual analog scale. We found that accuracy of visual motor imagery was correlated with the activity in the left visual cortex, as well as with bilateral sensorimotor regions. In contrast, vividness of visual motor imagery was associated with the activity in the right orbitofrontal cortex. However, there was no correlation in the brain activity between the right orbitofrontal cortex and visuomotor regions or between vividness and accuracy of motor imagery. In addition, we did not find any correlation in the kinesthetic imagery condition. We conclude that vividness of visual motor imagery is associated with the right orbitofrontal cortex and is independent of processes occurring in sensorimotor regions, which would be responsible for the accuracy of visual motor imagery.

Differential Effects of Transcranial Direct Current Stimulation (tDCS) Depending on Previous Musical Training.

Previous studies have shown that transcranial direct current stimulation (tDCS) facilitates motor performance, but individual differences such as baseline performance seem to influence this effect. Accordingly, musicians offer an inter-individual differences model due to anatomical and functional variances displayed among the motor cortex regions. The aim of the present work was to study if the baseline motor skill predicts whether tDCS can enhance motor learning. For that objective, we administered anodal (n = 20) or sham (n = 20) tDCS on the right primary motor cortex region of 40 right-handed healthy participants, who were divided into four groups: musicians (tDCS/sham) and non-musicians (tDCS/sham). We measured the skill index (SI) presented in the sequential finger-tapping task (SEQTAP) at baseline, during three 20 min/2 mA stimulation sessions, and in follow-up tests after 20 min and 8 days. Depending on the normality of the data distribution, statistical differences were estimated by ANOVA and Bonferroni post hoc test or Kruskal–Wallis and U Mann–Whitney. Results showed that musicians scored higher in baseline performance than non-musicians. The non-musicians who received tDCS scored higher than the sham group in the first and second stimulation session. This effect was extended to the 20 min and 8 days follow-up test. In musicians, there was no effect of tDCS. The present method seems to be suitable for the achievement of positive and consolidated tDCS effects on motor learning in inexperienced participants, but not in musicians. These data may have an implication for the rehabilitation of motor impairments, contributing to more individualized stimulation protocols.

Compromised tDCS-induced facilitation of motor consolidation in patients with multiple sclerosis

To investigate whether consolidation after motor learning can be facilitated by offline (post-training) transcranial direct current stimulation (tDCS) in patients with multiple sclerosis (MS). In this cross-sectional double-blind interventional study, effects of tDCS on motor consolidation were examined in 14 patients with relapsing remitting MS [median Expanded Disability Status Scale score 2.0 (range 1-4)] and 14 age- and sex-matched healthy controls. tDCS with the anode placed over the left primary motor cortex and the cathode placed over the right supraorbital region was applied immediately after a training session of an explicit sequential finger-tapping task that was performed with the right (dominant) hand. Task performance was retested after an interval of 8h to assess consolidation. Participants took part in two experimental sessions separated by at least 7days which differed with respect to type of post-training tDCS, i.e., sham and verum stimulation. Patients with MS performed worse than controls in functional motor tests and the motor sequence task. However, learning speed and magnitude of online performance increments during the training session were comparable to controls. While post-training tDCS facilitated motor consolidation in controls, patients with MS did not benefit from this type of intervention. Absence of post-training tDCS-induced facilitation of consolidation in patients with MS suggests that the interaction of tDCS with the motor consolidation network is inefficient. Identification of the underlying disease-related mechanisms will have important implications for the design of studies aiming to promote motor recovery in MS by non-invasive brain stimulation.

P104. The impact of timing of cerebellar anodal transcranial direct current stimulation on motor performance in a sequential finger tapping task

Background Transcranial direct current stimulation (tDCS) of the cerebellum could constitute an innovative approach in understanding the role of cerebellar function in healthy and pathological conditions. Recently, attention has grown toward cerebellar neuromodulation in motor learning using tDCS. An important point of discussion regarding this modulation is the optimal timing of tDCS. As this parameter could significantly influence the outcome, we aimed to compare the effect of anodal cerebellar tDCS applied at different times on the motor performance and retention using a sequential finger tapping task (FTT). Methods Fifty-six healthy young, right-handed subjects performed two days of FTT on a custom keyboard. The task was presented with OpenSesame software and lasted 40 s followed by 20 s rest forming one trial. Each participant performed 20 trials on the first day (20 min) and 10 trials on the following one (10 min). tDCS (2 mA, sponge electrodes of 25 cm2, duration 20 min) was applied to the ipsilateral cerebellar hemisphere on day 1 at the following times: (1) before ‘tDCS-before’, (2) sham during ‘tDCS-sham’, (3) active during ‘tDCS-active’ or (4) after the training ‘tDCS-after’. Motor skill performance and retention were assessed. Results All participants showed significant effects of learning ( p 0.0001 ). The mean performance on day 1 was significantly different ( p 0.0001 ): The tDCS-after group performed better than all the other groups, whereas the tDCS-active group performed worse than the tDCS-before group. Similarly, there was a significant difference in the mean performance on day 2 ( p 0.0001 ): tDCS-after was associated with a better performance on day 2, compared to tDCS-sham and tDCS-active. The tDCS-before group also performed better than the tDCS-sham or the tDCS-active groups. Motor skill retention was not different between the groups (p = 0.15). Discussion Cerebellar tDCS applied during the FTT (‘on-line’) interfered with task execution, resulting in an impaired performance on days 1 and 2 compared to the other groups. This inhibitory effect of anodal tDCS may caution against a simple transfer of tDCS’ effects on the motor cortex to regions with a different architecture like the cerebellum. It calls for a careful attention to the timing of stimulation when designing experiments with tDCS. Cerebellar tDCS did not facilitate the retention of the motor skill in the FTT – however, it cannot be excluded that young healthy subjects already performed at a near optimal level with little room for further improvement. Future work will evaluate the effect of cerebellar tDCS in a population where motor learning and cerebellar volume are known to decline.

Sigma frequency dependent motor learning in Williams syndrome

There are two basic stages of fine motor learning: performance gain might occur during practice (online learning), and improvement might take place without any further practice (offline learning). Offline learning, also called consolidation, has a sleep-dependent stage in terms of both speed and accuracy of the learned movement. Sleep spindle or sigma band characteristics affect motor learning in typically developing individuals. Here we ask whether the earlier found, altered sigma activity in a neurodevelopmental disorder (Williams syndrome, WS) predicts motor learning. TD and WS participants practiced in a sequential finger tapping (FT) task for two days. Although WS participants started out at a lower performance level, TD and WS participants had a comparable amount of online and offline learning in terms of the accuracy of movement. Spectral analysis of WS sleep EEG recordings revealed that motor accuracy improvement is intricately related to WS-specific NREM sleep EEG features in the 8–16 Hz range profiles: higher 11–13.5 Hz z-transformed power is associated with higher offline FT accuracy improvement; and higher oscillatory peak frequencies are associated with lower offline accuracy improvements. These findings indicate a fundamental relationship between sleep spindle (or sigma band) activity and motor learning in WS.