The acquisition of skilled motor performance: fast and slow experience-driven changes in primary motor cortex

Explicit benefits: Motor sequence acquisition and short-term retention in adults who do and do not stutter

Motor sequencing skills have been found to distinguish individuals who experience developmental stuttering from those who do not stutter, with these differences extending to non-verbal sequencing behaviour. Previous research has focused on measures of reaction time and practice under externally cued conditions to decipher the motor learning abilities of persons who stutter. Without the confounds of extraneous demands and sensorimotor processing, we investigated motor sequence learning under conditions of explicit awareness and focused practice among adults with persistent development stuttering. Across two consecutive practice sessions, 18 adults who stutter (AWS) and 18 adults who do not stutter (ANS) performed the finger-to-thumb opposition sequencing (FOS) task. Both groups demonstrated significant within-session performance improvements, as evidenced by fast on-line learning of finger sequences on day one. Additionally, neither participant group showed deterioration of their learning gains the following day, indicating a relative stabilization of finger sequencing performance during the off-line period. These findings suggest that under explicit and focused conditions, early motor learning gains and their short-term retention do not differ between AWS and ANS. Additional factors influencing motor sequencing performance, such as task complexity and saturation of learning, are also considered. Further research into explicit motor learning and its generalization following extended practice and follow-up in persons who stutter is warranted. The potential benefits of motor practice generalizability among individuals who stutter and its relevance to supporting treatment outcomes are suggested as future areas of investigation.

Involvement of the prefrontal cortex in motor sequence learning: A functional near-infrared spectroscopy (fNIRS) study

Our previous functional near-infrared spectroscopy (fNIRS) study on motor sequence learning (Polskaia et al., 2020) did not detect the same decrease in activity in the left dorsolateral prefrontal cortex (DLPFC) associated with movement automaticity, as reported by Wu et al. (2004). This was partly attributed to insufficient practice time to reach neural efficiency. Therefore, we sought to expand on our previous work to better understand the contribution of the prefrontal cortex (PFC) to motor sequence learning by examining learning across a longer period of time. Participants were randomly assigned to one of two groups: control or trained. fNIRS was acquired at three time points: pre-test, post-test, and retention. Participants performed four sequences (S1, S2, S3, and S4) of right-hand finger tapping. The trained group also underwent four days of practice of S1 and S2. No group differences in the left DLPFC and ventrolateral (VLPFC) were found between sessions for S1 and S2. Our findings revealed increased contribution from the right VLPFC in post-test for the trained group, which may reflect the active retrieval of explicit information from long-term memory. Our results suggest that despite additional practice time, explicit motor sequence learning requires the continued involvement of the PFC.

Anodal cerebellar stimulation increases cortical activation: Evidence for cerebellar scaffolding of cortical processing

While the cerebellum contributes to nonmotor task performance, the specific contributions of the structure remain unknown. One possibility is that the cerebellum allows for the offloading of cortical processing, providing support during task performance, using internal models. Here we used transcranial direct current stimulation to modulate cerebellar function and investigate the impact on cortical activation patterns. Participants (n = 74; 22.03 ± 3.44 years) received either cathodal, anodal, or sham stimulation over the right cerebellum before a functional magnetic resonance imaging scan during which they completed a sequence learning and a working memory task. We predicted that cathodal stimulation would improve, and anodal stimulation would hinder task performance and cortical activation. Behaviorally, anodal stimulation negatively impacted behavior during late-phase sequence learning. Functionally, we found that anodal cerebellar stimulation resulted in increased bilateral cortical activation, particularly in parietal and frontal regions known to be involved in cognitive processing. This suggests that if the cerebellum is not functioning optimally, there is a greater need for cortical resources.

Reactivation-induced motor skill modulation does not operate at a rapid micro-timescale level

Abundant evidence shows that consolidated memories are susceptible to modifications following their reactivation. Processes of memory consolidation and reactivation-induced skill modulation have been commonly documented after hours or days. Motivated by studies showing rapid consolidation in early stages of motor skill acquisition, here we asked whether motor skill memories are susceptible to modifications following brief reactivations, even at initial stages of learning. In a set of experiments, we collected crowdsourced online motor sequence data to test whether post-encoding interference and performance enhancement occur following brief reactivations in early stages of learning. Results indicate that memories forming during early learning are not susceptible to interference nor to enhancement within a rapid reactivation-induced time window, relative to control conditions. This set of evidence suggests that reactivation-induced motor skill memory modulation might be dependent on consolidation at the macro-timescale level, requiring hours or days to occur.

Investigation of the Relationships Between Beck Depression/Anxiety Scores and Neuropsychological Tests Scores with Lifestyle Behaviors in the Context of Neuroplasticity and Neurogenesis Approach

In this study, the relationships between lifestyle behaviors within the scope of neuroplasticity and neurogenesis approach and depression, anxiety and neuropsychological test scores were examined. As this study aimed to reveal the relationships between events or variables, it was designed using the "descriptive cross-sectional study" method, one of descriptive and relational research methods, was used. The data were collected from 117 students by the researchers using the Öktem Verbal Memory Test, WCST, Digit Span Test, Beck Depression Inventory, Beck Anxiety Scale and Lifestyle Behaviors Survey.According to the results, the quality of sport/exercise and the quality of life showed a significant difference in the depression model, while social support demonstrated a significant difference in the anxiety model. It was seen that those with high scores in life quality and in perceived social support had significantly lower depression and anxiety scores. Moreover, those with good levels of sleep quality, social interaction and nutrition had significantly lower depression scores.Both depression and anxiety scores of those who did sport/exercise, which was among the lifestyle behaviors, were found to be significantly lower. Lastly, the correlations between the neuropsychological test scores and the depression and anxiety scores were examined, and a significant positive correlation was found between both depression and anxiety scores and the "failure to maintain set" scores.

Does Motor Memory Reactivation through Practice and Post-Learning Sleep Modulate Consolidation?

Retrieving previously stored information makes memory traces labile again and can trigger restabilization in a strengthened or weakened form depending on the reactivation condition. Available evidence for long-term performance changes upon reactivation of motor memories and the effect of post-learning sleep on their consolidation remains scarce, and so does the data on the ways in which subsequent reactivation of motor memories interacts with sleep-related consolidation. Eighty young volunteers learned (Day 1) a 12-element Serial Reaction Time Task (SRTT) before a post-training Regular Sleep (RS) or Sleep Deprivation (SD) night, either followed (Day 2) by morning motor reactivation through a short SRTT testing or no motor activity. Consolidation was assessed after three recovery nights (Day 5). A 2 × 2 ANOVA carried on proportional offline gains did not evidence significant Reactivation (Morning Reactivation/No Morning Reactivation; p = 0.098), post-training Sleep (RS/SD; p = 0.301) or Sleep*Reactivation interaction (p = 0.257) effect. Our results are in line with prior studies suggesting a lack of supplementary performance gains upon reactivation, and other studies that failed to disclose post-learning sleep-related effects on performance improvement. However, lack of overt behavioural effects does not detract from the possibility of sleep- or reconsolidation-related covert neurophysiological changes underlying similar behavioural performance levels.

Early sleep after action observation and motor imagery training boosts improvements in manual dexterity

The systematic observation and imagination of actions promotes acquisition of motor skills. Furthermore, studies demonstrated that early sleep after practice enhances motor learning through an offline stabilization process. Here, we investigated behavioral effects and neurodynamical correlates of early sleep after action observation and motor imagery training (AO + MI-training) on motor learning in terms of manual dexterity. Forty-five healthy participants were randomized into three groups receiving a 3 week intervention consisting of AO + MI-training immediately before sleeping or AO + MI-training at least 12 h before sleeping or a control stimulation. AO + MI-training implied the observation and motor imagery of transitive manual dexterity tasks, whereas the control stimulation consisted of landscape video-clips observation. Manual dexterity was assessed using functional tests, kinematic and neurophysiological outcomes before and after the training and at 1-month follow-up. AO + MI-training improved manual dexterity, but subjects performing AO + MI-training followed by early sleep had significantly larger improvements than those undergoing the same training at least 12 h before sleeping. Behavioral findings were supported by neurodynamical correlates during motor performance and additional sleep-dependent benefits were also detected at 1 month follow-up. These findings introduce a new approach to enhance the acquisition of new motor skills or facilitate recovery in patients with motor impairments.

Improving old tricks as new: Young adults learn from repeating everyday activities

The notion that young healthy adults can substantially improve in activities that are part of their daily routine is often overlooked because it is assumed that such activities have come to be fully mastered. We followed, in young healthy adults, the effects of repeated executions of the Timed-Up-and-Go (TUG) task, a clinical test that assesses the ability to execute motor activities relevant to daily function-rising from a seated position, walking, turning and returning to a seated position. The participants (N = 15) performed 18 consecutive trials of the TUG in one session, and were retested on the following day and a week later. The participants were video recorded and wore inertial measurement units. Task execution times improved robustly; performance was well fitted by a power function, with large gains at the beginning of the session and nearing plateau in later trials, as one would expect in the learning of a novel task. Moreover, these gains were well retained overnight and a week later, with further gains accruing in the subsequent test-sessions. Significant intra-session and inter-session changes occurred in step kinematics as well; some aspects underwent inter-sessions recalibrations, but other aspects showed delayed inter-session changes, suggesting post-practice memory consolidation processes. Even common everyday tasks can be improved upon by practice; a small number of consecutive task repetitions can trigger lasting gains in young healthy individuals performing highly practiced routine tasks. This new learning in highly familiar tasks proceeded in a time-course characteristic of the acquisition of novel 'how to' (procedural) knowledge.

The effect of action observation combined with high-definition transcranial direct current stimulation on motor performance in healthy adults: A randomized controlled trial

Action observation (AO) can improve motor performance in humans, probably via the human mirror neuron system. In addition, there is some evidence that transcranial direct current stimulation (tDCS) can improve motor performance. However, it is yet to be determined whether AO combined with tDCS has an enhanced effect on motor performance. We investigated the effect of AO combined with high-definition tDCS (HD-tDCS) targeting the inferior parietal lobe (IPL) and inferior frontal gyrus (IFG), the main aggregates of the human mirror neuron system, on motor performance in healthy adults and compared the immediate vs. 24-h retention test effects (anodal electrodes were placed over these regions of interest). Sixty participants were randomly divided into three groups that received one of the following single-session interventions: (1) observation of a video clip that presented reaching movement sequences toward five lighted units + active HD-tDCS stimulation (AO + active HD-tDCS group); (2) observation of a video clip that presented the same reaching movement sequences + sham HD-tDCS stimulation (AO + sham HD-tDCS group); and (3) observation of a video clip that presented neutral movie while receiving sham stimulation (NM + sham HD-tDCS group). Subjects' reaching performance was tested before and immediately after each intervention and following 24 h. Subjects performed reaching movements toward units that were activated in the same order as the observed sequence during pretest, posttest, and retest. Occasionally, the sequence order was changed by beginning the sequence unexpectedly with a different activated unit. Outcome measures included mean Reaching Time and difference between the Reaching Time of the unexpected and expected reaching movements (Delta). In the posttest and retest, Reaching Time and Delta improved in the AO + sham HD-tDCS group compared to the NM + HD-sham tDCS group. In addition, at posttest, Delta improved in the AO + active HD-tDCS group compared to the NM + sham HD-tDCS group. It appears that combining a montage of active HD-tDCS, which targets the IPL and IFG, with AO interferes with the positive effects of AO alone on the performance of reaching movement sequences.

Key role of Rho GTPases in motor disorders associated with neurodevelopmental pathologies

Growing evidence suggests that Rho GTPases and molecules involved in their signaling pathways play a major role in the development of the central nervous system (CNS). Whole exome sequencing (WES) and de novo examination of mutations, including SNP (Single Nucleotide Polymorphism) in genes coding for the molecules of their signaling cascade, has allowed the recent discovery of dominant autosomic mutations and duplication or deletion of candidates in the field of neurodevelopmental diseases (NDD). Epidemiological studies show that the co-occurrence of several of these neurological pathologies may indeed be the rule. The regulators of Rho GTPases have often been considered for cognitive diseases such as intellectual disability (ID) and autism. But, in a remarkable way, mild to severe motor symptoms are now reported in autism and other cognitive NDD. Although a more abundant litterature reports the involvement of Rho GTPases and signaling partners in cognitive development, molecular investigations on their roles in central nervous system (CNS) development or degenerative CNS pathologies also reveal their role in embryonic and perinatal motor wiring through axon guidance and later in synaptic plasticity. Thus, Rho family small GTPases have been revealed to play a key role in brain functions including learning and memory but their precise role in motor development and associated symptoms in NDD has been poorly scoped so far, despite increasing clinical data highlighting the links between cognition and motor development. Indeed, early impairements in fine or gross motor performance is often an associated feature of NDDs, which then impact social communication, cognition, emotion, and behavior. We review here recent insights derived from clinical developmental neurobiology in the field of Rho GTPases and NDD (autism spectrum related disorder (ASD), ID, schizophrenia, hypotonia, spastic paraplegia, bipolar disorder and dyslexia), with a specific focus on genetic alterations affecting Rho GTPases that are involved in motor circuit development.

Exergaming in older adults: the effects of game characteristics on brain activity and physical activity

Introduction

Exergames are increasingly used in rehabilitation settings for older adults to train physical and cognitive abilities. To meet the potential that exergames hold, they need to be adapted to the individual abilities of the player and their training objectives. Therefore, it is important to know whether and how game characteristics affect their playing. The aim of this study is to investigate the effect of two different kinds of exergame (step game and balance game) played at two difficulty levels on brain activity and physical activity.

Methods

Twenty-eight older independently living adults played two different exergames at two difficulty levels each. In addition, the same movements as during gaming (leaning sideways with feet in place and stepping sideways) were performed as reference movements. Brain activity was recorded using a 64-channel EEG system to assess brain activity, while physical activity was recorded using an accelerometer at the lower back and a heart rate sensor. Source-space analysis was applied to analyze the power spectral density in theta (4 Hz-7 Hz) and alpha-2 (10 Hz-12 Hz) frequency bands. Vector magnitude was applied to the acceleration data.

Results

Friedman ANOVA revealed significantly higher theta power for the exergaming conditions compared to the reference movement for both games. Alpha-2 power showed a more diverse pattern which might be attributed to task-specific conditions. Acceleration decreased significantly from the reference movement to the easy condition to the hard condition for both games.

Discussion

The results indicate that exergaming increases frontal theta activity irrespective of type of game or difficulty level, while physical activity decreases with increasing difficulty level. Heart rate was found to be an inappropriate measure in this population older adults. These findings contribute to understanding of how game characteristics affect physical and cognitive activity and consequently need to be taken into account when choosing appropriate games and game settings for exergame interventions.

Robust enhancement of motor sequence learning with 4 mA transcranial electric stimulation

BACKGROUND AND OBJECTIVES

Motor learning experiments with transcranial direct current stimulation (tDCS) at 2 mA have produced mixed results. We hypothesize that tDCS boosts motor learning provided sufficiently high field intensity on the motor cortex.

METHODS

In a single-blinded design, 108 healthy participants received either anodal (N = 36) or cathodal (N = 36) tDCS at 4 mA total, or no stimulation (N = 36) while they practiced a 12-min sequence learning task. Anodal stimulation was delivered across four electrode pairs (1 mA each), with anodes above the right parietal lobe and cathodes above the right frontal lobe. Cathodal stimulation, with reversed polarities, served as an active control for sensation, while the no-stimulation condition established baseline performance. fMRI-localized targets on the primary motor cortex in 10 subjects were used in current flow models to optimize electrode placement for maximal field intensity. A single electrode montage was then selected for all participants.

RESULTS

We found a significant difference in performance with anodal vs. cathodal stimulation (Cohen's d = 0.71) and vs. no stimulation (d = 0.56). This effect persisted for at least 1 h, and subsequent learning for a new sequence and the opposite hand also improved. Sensation ratings were comparable in the active groups and did not exceed moderate levels. Current flow models suggest the new electrode montage can achieve stronger motor cortex polarization than alternative montages.

CONCLUSION

The present paradigm shows a medium to large effect size and is well-tolerated. It may serve as a go-to experiment for future studies on motor learning and tDCS.

Motor Memory Consolidation Deficits in Parkinson's Disease: A Systematic Review with Meta-Analysis

BACKGROUND

The ability to encode and consolidate motor memories is essential for persons with Parkinson's disease (PD), who usually experience a progressive loss of motor function. Deficits in memory encoding, usually expressed as poorer rates of skill improvement during motor practice, have been reported in these patients. Whether motor memory consolidation (i.e., motor skill retention) is also impaired is unknown.

OBJECTIVE

To determine whether motor memory consolidation is impaired in PD compared to neurologically intact individuals.

METHODS

We conducted a pre-registered systematic review (PROSPERO: CRD42020222433) following PRISMA guidelines that included 46 studies.

RESULTS

Meta-analyses revealed that persons with PD have deficits in retaining motor skills (SMD = -0.17; 95% CI = -0.32, -0.02; p = 0.0225). However, these deficits are task-specific, affecting sensory motor (SMD = -0.31; 95% CI -0.47, -0.15; p = 0.0002) and visuomotor adaptation (SMD = -1.55; 95% CI = -2.32, -0.79; p = 0.0001) tasks, but not sequential fine motor (SMD = 0.17; 95% CI = -0.05, 0.39; p = 0.1292) and gross motor tasks (SMD = 0.04; 95% CI = -0.25, 0.33; p = 0.7771). Importantly, deficits became non-significant when augmented feedback during practice was provided, and additional motor practice sessions reduced deficits in sensory motor tasks. Meta-regression analyses confirmed that deficits were independent of performance during encoding, as well as disease duration and severity.

CONCLUSION

Our results align with the neurodegenerative models of PD progression and motor learning frameworks and emphasize the importance of developing targeted interventions to enhance motor memory consolidation in PD.

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

Background

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.

Objective

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.

Methods

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.

Results

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.

Conclusion

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.

The effect of interictal epileptic discharges and following spindles on motor sequence learning in epilepsy patients

PURPOSE

Interictal epileptic discharges (IEDs) are known to affect cognitive function in patients with epilepsy, but the mechanism has not been elucidated. Sleep spindles appearing in synchronization with IEDs were recently demonstrated to impair memory consolidation in rat, but this has not been investigated in humans. On the other hand, the increase of sleep spindles at night after learning is positively correlated with amplified learning effects during sleep for motor sequence learning. In this study, we examined the effects of IEDs and IED-coupled spindles on motor sequence learning in patients with epilepsy, and clarified their pathological significance.

MATERIALS AND METHODS

Patients undergoing long-term video-electroencephalography (LT-VEEG) at our hospital from June 2019 to November 2021 and age-matched healthy subjects were recruited. Motor sequence learning consisting of a finger-tapping task was performed before bedtime and the next morning, and the improvement rate of performance was defined as the sleep-dependent learning effect. We searched for factors associated with the changes in learning effect observed between the periods of when antiseizure medications (ASMs) were withdrawn for LT-VEEG and when they were returned to usual doses after LT-VEEG.

RESULTS

Excluding six patients who had epileptic seizures at night after learning, nine patients and 11 healthy subjects were included in the study. In the patient group, there was no significant learning effect when ASMs were withdrawn. The changes in learning effect of the patient group during ASM withdrawal were not correlated with changes in sleep duration or IED density; however, they were significantly negatively correlated with changes in IED-coupled spindle density.

CONCLUSION

We found that the increase of IED-coupled spindles correlated with the decrease of sleep-dependent learning effects of procedural memory. Pathological IED-coupled sleep spindles could hinder memory consolidation, that is dependent on physiological sleep spindles, resulting in cognitive dysfunction in patients with epilepsy.

Effects of short-term arm immobilization on motor skill acquisition

Learning to sequence movements is necessary for skillful interaction with the environment. Neuroplasticity, particularly long-term potentiation (LTP), within sensorimotor networks underlies the acquisition of motor skill. Short-term immobilization of the arm, even less than 12 hours, can reduce corticospinal excitability and increase the capacity for LTP-like plasticity within the contralateral primary motor cortex. However, it is still unclear whether short-term immobilization influences motor skill acquisition. The current study aimed to evaluate the effect of short-term arm immobilization on implicit, sequence-specific motor skill acquisition using a modified Serial Reaction Time Task (SRTT). Twenty young, neurotypical adults underwent a single SRTT training session after six hours of immobilization of the non-dominant arm or an equivalent period of no immobilization. Our results demonstrated that participants improved SRTT performance overall after training, but there was no evidence of an effect of immobilization prior to task training on performance improvement. Further, improvements on the SRTT were not sequence-specific. Taken together, motor skill acquisition for sequential, individuated finger movements improved following training but the effect of six hours of immobilization was difficult to discern.

Skill-learning by observation-training with patients after traumatic brain injury

Traumatic brain injury (TBI) is a major cause of death and disability in Western society, and often results in functional and neuropsychological abnormalities. Memory impairment is one of the most significant cognitive implications after TBI. In the current study we investigated procedural memory acquisition by observational training in TBI patients. It was previously found that while practicing a new motor skill, patients engage in all three phases of skill learning–fast acquisition, between-session consolidation, and long-term retention, though their pattern of learning is atypical compared to healthy participants. A different set of studies showed that training by observing a motor task, generally prompted effective acquisition and consolidation of procedural knowledge in healthy participants. The aim of our study was to (i) evaluate the potential benefit of action observation in TBI patients. (ii) Examine the possibility of general improvement in performance between the first (24 h post-training) and second (2 weeks post-training) stage of the study. (iii) Investigate the link between patients’ ability to benefit from observational learning (via performance gains–speed and accuracy) and common measures of injury (such as severity of injury, functional and cognitive measures).

Motor learning-induced new dendritic spines are preferentially involved in the learned task than existing spines

Learning induces the formation of new synapses in addition to changes of existing synapse strength. However, it remains unclear whether new synapses serve different functions from existing synapses. By performing two-photon structural and Ca²⁺ imaging of postsynaptic dendritic spines in layer 2/3 pyramidal neurons, we show that new spine formation increases in the mouse motor cortex 8-24 h after motor training. New spines, not existing spine populations, are preferentially active when mice perform the learned task rather than a new task. New spine activity is also more synchronized with dendritic/somatic activity when the learned task, not a new task, is carried out. Furthermore, new spines are formed to increase the task specificity in a subset of neurons, and their survival is not affected when a new task is learned. These findings suggest that newly formed synapses preferentially increase the task specificity of neurons over existing synapses at the retention stage of motor learning.

Impaired feedforward control of movements in pianists with focal dystonia

Learning accurate and fast movements typically accompanies the modulation of feedforward control. Nevertheless, it remains unclear how motor skill learning modulates feedforward control, such as through maladaptation of the sensorimotor system by extensive training (e.g., task-specific dystonia). Here, we examined the modulation of feedforward control through motor skill learning while focusing on the motion of piano playing at either a natural tempo or the fastest tempo. The current study compared the kinematics and keypress data among individuals in three groups: healthy and well-trained pianists (i.e., subjects with skill learning), non-musicians (i.e., subjects without skill learning), and patients with focal-hand dystonia (FHD) (i.e., subjects with maladaptation by skill learning). Compared to healthy pianists, patients with FHD showed impairment in some feedforward motion components that are relevant to classifying the two playing tempi. However, while focusing on motion components that are irrelevant to the tempo classification, patients with FHD showed movements comparable to those of healthy pianists. Furthermore, patients with FHD demonstrated significantly slower movement times than healthy pianists. Our results suggest that maladaptation by skill learning affects parts of feedforward control rather than its entirety. Nevertheless, the affected feedforward components are relevant to performing movements as fast as possible, which may underlie the speed dependence of dystonic symptoms.

Differences in implicit motor learning between adults who do and do not stutter

Implicit learning allows us to acquire complex motor skills through repeated exposure to sensory cues and repetition of motor behaviours, without awareness or effort. Implicit learning is also critical to the incremental fine-tuning of the perceptual-motor system. To understand how implicit learning and associated domain-general learning processes may contribute to motor learning differences in people who stutter, we investigated implicit finger-sequencing skills in adults who do (AWS) and do not stutter (ANS) on an Alternating Serial Reaction Time task. Our results demonstrated that, while all participants showed evidence of significant sequence-specific learning in their speed of performance, male AWS were slower and made fewer sequence-specific learning gains than their ANS counterparts. Although there were no learning gains evident in accuracy of performance, AWS performed the implicit learning task more accurately than ANS, overall. These findings may have implications for sex-based differences in the experience of developmental stuttering, for the successful acquisition of complex motor skills during development by individuals who stutter, and for the updating and automatization of speech motor plans during the therapeutic process.

A Randomized Controlled Trial With Female Teachers: Are there Differences Between and Within the Outcomes in Voice Therapy Groups With and Without Carryover Strategies?

PURPOSE

We investigated if outcomes differ between voice therapy groups systematically using carryover strategies (attempts to generalize new vocal skills outside the clinic) and voice therapy with no emphasis on any generalizing process (here referred to as traditional voice therapy).

METHOD

A randomized controlled trial was conducted. Participants (53 female teachers with voice disorders) were randomly allocated into three groups: Carryover (a group receiving voice therapy using carryover strategies), Trad (a group receiving voice therapy with no emphasis on any generalizing process), Controls (a group on an eight-week non-therapy period). Prior to the trial a direct laryngoscopy was performed with a videolaryngostroboscopy system and/or nasofaryngofiberoscope with stroboscopy. Before and after therapy and at follow-up a voice evaluation protocol was implemented consisting of subjective assessments (Questionnaire on Voice Symptoms, and the Voice Activity and Participation Profile; VAPP), and objective measurements (voice sample recordings, acoustic analysis [SPL, sound pressure level; f0, fundamental frequency; alpha-ratio, tilt of the sound spectrum slope]).

RESULTS

No differences were found between the groups. Several significant changes occurred within the groups between initial phase vs. post-therapy and initial phase vs. follow-up. In the Carryover group text reading the alpha-ratio became lower (P = 0.011) and spontaneous speech f0 increased (P = 0.024) after the therapy and [a:] SPL increased (P = 0.042) at follow-up. In the Trad group post-therapy [a:] alpha-ratio became lower (P = 0.012) and spontaneous speech f0 decreased (P = 0.034). After therapy VAPP scores showed improvement in voice-related quality of life in both therapy groups (Carryover P = 0.003; Trad P = 0.01) but only in Carryover at follow-up (P = 0.000). Voice symptoms decreased in the Carryover group post-therapy (P = 0.001) and at follow-up (P = 0.000) and after Controls' eight-week non-therapy period (P = 0.003).

CONCLUSION

The results showed that carryover strategies give no additional advantages in voice therapy. However, the decreasing trend in the Carryover group's voice complaints at follow-up would suggest that carryover strategies may have long-lasting effects. The results also confirm that voice therapy is efficient in improving voice-related quality of life.

Motor training is improved by concurrent application of slow oscillating transcranial alternating current stimulation to motor cortex

Physical exercise and neurorehabilitation involve repetitive training that can induce changes in motor performance arising from neuroplasticity. Retention of these motor changes occurs via an encoding process, during which rapid neuroplastic changes occur in response to training. Previous studies show that transcranial alternating current stimulation (tACS), a form of non-invasive brain stimulation, can enhance encoding of a cognitive learning task during wakefulness. However, the effect of tACS on motor processes in the awake brain is unknown. In this study, forty-two healthy 18–35 year old participants received either 0.75 Hz (active) tACS (or sham stimulation) for 30 min during a ballistic thumb abduction motor training task. Training-related behavioural effects were quantified by assessing changes in thumb abduction acceleration, and neuroplastic changes were quantified by measuring motor evoked potential (MEP) amplitude of the abductor pollicis brevis muscle. These measures were reassessed immediately after the motor training task to quantify short-term changes, and then 24 h later to assess longer-term changes. Thumb abduction acceleration in both active and sham stimulation conditions increased immediately after the motor learning, consistent with effective training. Critically, participants in the active group maintained significantly higher thumb acceleration 24 h later (t₄₀ = 2.810, P = 0.044). There were no significant changes or inter-group differences in MEPs for both conditions. The results suggest that 0.75 Hz tACS applied during motor training enhances the effectiveness of motor training, which manifests as enhancement in longer-term task benefits.

Sensorimotor performance after high-definition transcranial direct current stimulation over the primary somatosensory or motor cortices in men versus women

The primary somatosensory (S1) cortex is a central structure in motor performance. However, transcranial direct current stimulation (tDCS) research aimed at improving motor performance usually targets the primary motor cortex (M1). Recently, sex was found to mediate tDCS response. Thus, we investigated whether tDCS with an anodal electrode placed over S1 improves motor performance and sensation perception in men versus women. Forty-five participants randomly received 15-min high-definition tDCS (HD-tDCS) at 1 mA to S1, M1, or sham stimulation. Reaching performance was tested before and immediately following stimulation. Two-point orientation discrimination (TPOD) of fingers and proprioception of a reaching movement were also tested. Although motor performance did not differ between groups, reaching reaction time improved in the M1 group men. Reaching movement time and endpoint error improved in women and men, respectively. Correct trials percentage for TPOD task was higher in the S1 compared to the M1 group in the posttest and improved only in the S1 group. Reaching movement time for the proprioception task improved, overall, and endpoint error did not change. Despite the reciprocal connections between S1 and M1, effects of active tDCS over S1 and M1 may specifically influence sensation perception and motor performance, respectively. Also, sex may mediate effects of HD-tDCS on motor performance.

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

Our 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.

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The update of internal forward models involves cerebellar neural adaptations

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Mental practice is assumed to engage internal forward models

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Cerebellar-brain Inhibition was probed by TMS before and after mental practice

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Mental practice reduces Cerebellar-brain Inhibition and may update internal models

Sleep and Athletic Performance: Impacts on Physical Performance, Mental Performance, Injury Risk and Recovery, and Mental Health: An Update

Sleep health is an important consideration for athletic performance. Athletes are at high risk of insufficient sleep duration, poor sleep quality, daytime sleepiness and fatigue, suboptimal sleep schedules, irregular sleep schedules, and sleep and circadian disorders. These issues likely have an impact on athletic performance via several domains. Sleep loss and/or poor sleep quality can impair muscular strength, speed, and other aspects of physical performance. Sleep issues can also increase risk of concussions and other injuries and impair recovery after injury. Cognitive performance is also impacted in several domains, including vigilance, learning and memory, decision making, and creativity.

Selective behavioural impairments in mice heterozygous for the cross disorder psychiatric risk gene DLG2

Mutations affecting DLG2 are emerging as a genetic risk factor associated with neurodevelopmental psychiatric disorders including schizophrenia, autism spectrum disorder, and bipolar disorder. Discs large homolog 2 (DLG2) is a member of the membrane-associated guanylate kinase protein superfamily of scaffold proteins, a component of the post-synaptic density in excitatory neurons and regulator of synaptic function and plasticity. It remains an important question whether and how haploinsuffiency of DLG2 contributes to impairments in basic behavioural and cognitive functions that may underlie symptomatic domains in patients that cross diagnostic boundaries. Using a heterozygous Dlg2 mouse model we examined the impact of reduced Dlg2 expression on functions commonly impaired in neurodevelopmental psychiatric disorders including motor co-ordination and learning, pre-pulse inhibition and habituation to novel stimuli. The heterozygous Dlg2 mice exhibited behavioural impairments in long-term motor learning and long-term habituation to a novel context, but not motor co-ordination, initial responses to a novel context, PPI of acoustic startle or anxiety. We additionally showed evidence for the reduced regulation of the synaptic plasticity-associated protein cFos in the motor cortex during motor learning. The sensitivity of selective behavioural and cognitive functions, particularly those dependent on synaptic plasticity, to reduced expression of DLG2 give further credence for DLG2 playing a critical role in specific brain functions but also a mechanistic understanding of symptom expression shared across psychiatric disorders.

Resting state fast brain dynamics predict interindividual variability in motor performance

Motor learning features rapid enhancement during practice then offline post-practice gains with the reorganization of related brain networks. We hypothesised that fast transient, sub-second variations in magnetoencephalographic (MEG) network activity during the resting-state (RS) reflect early learning-related plasticity mechanisms and/or interindividual motor variability in performance. MEG RS activity was recorded before and 20 min after motor learning. Hidden Markov modelling (HMM) of MEG power envelope signals highlighted 8 recurrent topographical states. For two states, motor performance levels were associated with HMM temporal parameters both in pre- and post-learning resting-state sessions. However, no association emerged with offline changes in performance. These results suggest a trait-like relationship between spontaneous transient neural dynamics at rest and interindividual variations in motor abilities. On the other hand, transient RS dynamics seem not to be state-dependent, i.e., modulated by learning experience and reflect neural plasticity, at least on the short timescale.

A meta-analysis on neural changes of cognitive training for mental disorders in executive function tasks: increase or decrease brain activation?

BACKGROUND

Cognitive impairment is often found in patients with psychiatric disorders, and cognitive training (CT) has been shown to help these patients. To better understand the mechanisms of CT, many neuroimaging studies have investigated the neural changes associated with it. However, the results of those studies have been inconsistent, making it difficult to draw conclusions from the literature. Therefore, the objective of this meta-analysis was to identify consistent patterns in the literature of neural changes associated with CT for psychiatric disorders.

METHODS

We searched for cognitive training imaging studies in PubMed, Cochrane library, Scopus, and ProQuest electronic databases. We conducted an activation likelihood estimation (ALE) for coordinate-based meta-analysis of neuroimaging studies, conduct behavioral analysis of brain regions identified by ALE analysis, conduct behavioral analysis of brain regions identified by ALE analysis, and then created a functional meta-analytic connectivity model (fMACM) of the resulting regions.

RESULTS

Results showed that CT studies consistently reported increased activation in the left inferior frontal gyrus (IFG) and decreased activation in the left precuneus and cuneus from pre- to post- CT.

CONCLUSION

CT improves cognitive function by supporting language and memory function, and reducing neuronal resources associated with basic visual processing.

Motor skill learning decreases movement variability and increases planning horizon

We investigated motor skill learning using a path tracking task, where human subjects had to track various curved paths at a constant speed while maintaining the cursor within the path width. Subjects' accuracy increased with practice, even when tracking novel untrained paths. Using a "searchlight" paradigm, where only a short segment of the path ahead of the cursor was shown, we found that subjects with a higher tracking skill differed from the novice subjects in two respects. First, they had lower movement variability, in agreement with previous findings. Second, they took a longer section of the future path into account when performing the task, i.e. had a longer planning horizon. We estimate that between one third and one half of the performance increase in the expert group was due to the longer planning horizon. An optimal control model with a fixed horizon (receding horizon control) that increases with tracking skill quantitatively captured the subjects' movement behaviour. These findings demonstrate that human subjects not only increase their motor acuity but also their planning horizon when acquiring a motor skill.

Effects of Sleep on Language and Motor Consolidation: Evidence of Domain General and Specific Mechanisms

The current study explores the effects of time and sleep on the consolidation of a novel language learning task containing both item-specific knowledge and the extraction of grammatical regularities. We also compare consolidation effects in language and motor sequence learning tasks, to ask whether consolidation mechanisms are domain general. Young adults learned to apply plural inflections to novel words based on morphophonological rules embedded in the input, and learned to type a motor sequence using a keyboard. Participants were randomly assigned into one of two groups, practicing each task during either the morning or evening hours. Both groups were retested 12 and 24 hours post-training. Performance on frequent trained items in the language task stabilized only following sleep, consistent with a hippocampal mechanism for item-specific learning. However, regularity extraction, indicated by generalization to untrained items in the linguistic task, as well as performance on motor sequence learning, improved 24 hours post-training, irrespective of the timing of sleep. This consolidation process is consistent with a frontostriatal skill-learning mechanism, common across the language and motor domains. This conclusion is further reinforced by cross-domain correlations at the individual level between improvement across 24 hours in the motor task and in the low-frequency trained items in the linguistic task, which involve regularity extraction. Taken together, our results at the group and individual levels suggest that some aspects of consolidation are shared across the motor and language domains, and more specifically, between motor sequence learning and grammar learning.

Single session transcranial direct current stimulation to the primary motor cortex fails to enhance early motor sequence learning in Parkinson's disease

INTRODUCTION

Explicit motor sequence learning is impaired in Parkinson's disease (PD). Transcranial direct current stimulation (tDCS) applied over the motor cortex in healthy can improve explicit motor learning, but comparative effects in PD are unknown. This exploratory study aims to examine the effect of single session tDCS on explicit motor sequence learning in PD.

METHODS

Thirty-three people with mild to moderate PD learnt a short and long finger tapping sequence with their right hand. Participants received either anodal, cathodal, or sham tDCS applied over the left primary motor cortex during task practice. Single- and dual-task finger tapping performance was assessed before and after task practice and functional near-infrared spectroscopy used to measure task related changes of oxygenated haemoglobin.

RESULTS

Finger tapping performance of short and long sequences under single-task conditions significantly improved following practice (p = 0.010 and p < 0.001, respectively). A condition-by-time interaction trend was observed for the long finger tapping sequence (p = 0.069) driven by improved performance in the cathodal (p = 0.001) and sham (p < 0.001) tDCS conditions, but not anodal tDCS (p = 0.198). The primary and premotor cortex and supplementary motor area were active in all tasks. No interaction or main effects were observed for task related changes of oxygenated haemoglobin.

CONCLUSIONS

PD patients retain the capacity to learn an explicit sequence of movements. Motor cortex tDCS does not improve explicit motor learning in PD and anodal tDCS may even suppress the rate of learning.

The Effects of Virtual Reality Nonphysical Mental Training on Coordination and Skill Transfer in Healthy Adults

CONTEXT

Mental training is a promising method to improve motor skills. However, transfer of these improvements to different skills or functional activities is still unclear. The purpose of this study was to investigate the effects of mental balance training programs on motor coordination and skill transfer.

DESIGN

Randomized controlled trial.

METHODS

Fifty-seven healthy adults (28 females and 29 males) aged between 18 and 25 years participated in this study. Participants were randomly assigned to 3 groups: virtual reality (VR) mental training group, conventional mental training group, and control group. The training program included action observation and motor imagery practice with balance exercise videos. The VR mental training group trained with a VR head-mounted display and the conventional mental training group trained with a nonimmersive computer monitor for 30 minutes, 3 days per week, for 4 weeks. Coordination skills were tested with 2 separate custom-made obstacle course tests (OCT-1 and OCT-2). OCT tests included crouching, turning, leaning, stepping over, changing direction, walking on various surfaces, or using repeated hand and arm movement tasks. OCT-1 was used to investigate the effects of mental exercises on coordination skills, and OCT-2 to investigate transfer effects for novel tasks. Test time (total and corrected) and error types (minor, major, and total) were recorded. Touching an obstacle without changing its position was classified as a minor error, and changing its position was a major error.

RESULTS

OCT-1 test time and number of errors significantly decreased in the VR mental training and conventional mental training groups, but not in the control group. The number of minor errors was only decreased in the VR mental training group. For OCT-2, total and corrected time were not significantly different between the groups. However, both training groups were significantly superior to the control group for all types of errors.

CONCLUSIONS

Our findings suggest that both training interventions can significantly improve coordination and skill transfer test results. In addition, VR mental training may have some advantages over conventional mental training. These findings are promising for the use of mental training for prevention and rehabilitation in special populations.

Preserved motor memory in Parkinson's disease

Patients with Parkinson's disease, who lose the dopaminergic projections to the striatum, are impaired in certain aspects of motor learning. Recent evidence suggests that, in addition to its role in motor performance, the striatum plays a key role in the memory of motor learning. Whether Parkinson's patients have impaired motor memory and whether motor memory is modulated by dopamine at the time of initial learning is unknown. To address these questions, we measured memory of a learned motor sequence in Parkinson's patients who were either On or Off their dopaminergic medications at the time of initial learning. We compared them to a group of older and younger controls. Contrary to our predictions, motor memory was not impaired in patients compared to older controls, and was not influenced by dopamine state at the time of initial learning. To probe post-learning consolidation processes, we also tested whether learning a new sequence shortly after learning the initial sequence would interfere with later memory. We found that, in contrast to younger adults, neither older adults nor patients were susceptible to this interference. These findings suggest that motor memory is preserved in Parkinson's patients and raise the possibility that motor memory in patients is supported by compensatory non-dopamine sensitive mechanisms. Furthermore, given the similar performance characteristics observed in the patients and older adults and the absence of an effect of dopamine, these results raise the possibility that aging and Parkinson's disease affect motor memory in similar ways.

Intracortical facilitation and inhibition in human primary motor cortex during motor skill acquisition

The primary motor cortex (M1) is critical for movement execution, but its role in motor skill acquisition remains elusive. Here, we examine the role of M1 intracortical circuits during skill acquisition. Paired-pulse transcranial magnetic stimulation (TMS) paradigms of short-interval intracortical facilitation (SICF) and inhibition (SICI) were used to assess excitatory and inhibitory circuits, respectively. We hypothesised that intracortical facilitation and inhibition circuits in M1 would be modulated to support acquisition of a novel visuomotor skill. Twenty-two young, neurologically healthy adults trained with their nondominant hand on a skilled and non-skilled sequential visuomotor isometric finger abduction task. Electromyographic recordings were obtained from the nondominant first dorsal interosseous (FDI) muscle. Corticomotor excitability, SICF, and SICI were examined before, at the midway point, and after the 10-block motor training. SICI was assessed using adaptive threshold-hunting procedures. Task performance improved after the skilled, but not non-skilled, task training, which likely reflected the increase in movement speed during training. The amplitudes of late SICF peaks were modulated with skilled task training. There was no modulation of the early SICF peak, SICI, and corticomotor excitability with either task training. There was also no association between skill acquisition and SICF or SICI. The findings indicate that excitatory circuitries responsible for the generation of late SICF peaks, but not the early SICF peak, are modulated in motor skill acquisition for a sequential visuomotor isometric finger abduction task.

Differences between adults and adolescents in responding to hip and knee pattern feedback during gait

Visual feedback techniques have shown potential in interventions aiming to retrain deviated gait patterns. Understanding the abilities of different age groups to modify their gait is needed to optimize interventions. Twelve adults (6F, 6 M; 26.3 ± 5.9 yrs.) and twelve adolescents (4F, 8 M; 13.6 ± 2.3 yrs) without disabilities participated in one training session. During the session, the responses to a visual kinematic feedback task in which one hip or knee target pattern was modified while unmodified target patterns were maintained in the other hip and knee joints were investigated. Limb orientation and acceleration data were collected using Inertial Measurement Units (IMU) (Xsens Awinda, Enschede, The Netherlands) with a sampling frequency of 60 Hz. Adults tended to outperform adolescents in tracking modified target patterns and showed smaller errors in unmodified regions of modified patterns (p = 0.045); they also outperformed adolescents in unmodified joints (Contralateral Hip: p = 0.003; Contralateral Knee: p = 0.002; Ipsilateral Joint: p = 0.048). These findings suggest different levels of awareness of the need and/or ability to minimize errors across joints, in turn suggesting the need for specialization of training for these age groups.

Smoothness discriminates physical from motor imagery practice of arm reaching movements

Physical practice (PP) and motor imagery practice (MP) lead to the execution of fast and accurate arm movements. However, there is currently no information about the influence of MP on movement smoothness, nor about which performance parameters best discriminate these practices. In the current study, we assessed motor performances with an arm pointing task with constrained precision before and after PP (n= 15), MP (n= 15), or no practice (n= 15). We analyzed gains between Pre- and Post-Test for five performance parameters: movement duration, mean and maximal velocities, total displacements, and the number of velocity peaks characterizing movement smoothness. The results showed an improvement of performance after PP and MP for all parameters, except for total displacements. The gains for movement duration, and mean and maximal velocities were statistically higher after PP and MP than after no practice, and comparable between practices. However, motor gains for the number of velocity peaks were higher after PP than MP, suggesting that movements were smoother after PP than after MP. A discriminant analysis also identified the number of velocity peaks as the most relevant parameter that differentiated PP from MP. The current results provide evidence that PP and MP specifically modulate movement smoothness during arm reaching tasks. This difference may rely on online corrections through sensory feedback integration, available during PP but not during MP.

How Learning to Read Changes the Listening Brain

Reading acquisition reorganizes existing brain networks for speech and visual processing to form novel audio-visual language representations. This requires substantial cortical plasticity that is reflected in changes in brain activation and functional as well as structural connectivity between brain areas. The extent to which a child's brain can accommodate these changes may underlie the high variability in reading outcome in both typical and dyslexic readers. In this review, we focus on reading-induced functional changes of the dorsal speech network in particular and discuss how its reciprocal interactions with the ventral reading network contributes to reading outcome. We discuss how the dynamic and intertwined development of both reading networks may be best captured by approaching reading from a skill learning perspective, using audio-visual learning paradigms and longitudinal designs to follow neuro-behavioral changes while children's reading skills unfold.

Offline low-frequency rTMS of the primary and premotor cortices does not impact motor sequence memory consolidation despite modulation of corticospinal excitability

Motor skills are acquired and refined across alternating phases of practice (online) and subsequent consolidation in the absence of further skill execution (offline). Both stages of learning are sustained by dynamic interactions within a widespread motor learning network including the premotor and primary motor cortices. Here, we aimed to investigate the role of the dorsal premotor cortex (dPMC) and its interaction with the primary motor cortex (M1) during motor memory consolidation. Forty-eight healthy human participants (age 22.1 ± 3.1 years) were assigned to three different groups corresponding to either low-frequency (1 Hz) repetitive transcranial magnetic stimulation (rTMS) of left dPMC, rTMS of left M1, or sham rTMS. rTMS was applied immediately after explicit motor sequence training with the right hand. Motor evoked potentials were recorded before training and after rTMS to assess potential stimulation-induced changes in corticospinal excitability (CSE). Participants were retested on motor sequence performance after eight hours to assess consolidation. While rTMS of dPMC significantly increased CSE and rTMS of M1 significantly decreased CSE, no CSE modulation was induced by sham rTMS. However, all groups demonstrated similar significant offline learning indicating that consolidation was not modulated by the post-training low-frequency rTMS intervention despite evidence of an interaction of dPMC and M1 at the level of CSE. Motor memory consolidation ensuing explicit motor sequence training seems to be a rather robust process that is not affected by low-frequency rTMS-induced perturbations of dPMC or M1. Findings further indicate that consolidation of explicitly acquired motor skills is neither mediated nor reflected by post-training CSE.

Changes of neuroplasticity in cortical motor control of human masseter muscle related to orthodontic treatment

BACKGROUND

Orthodontic treatment is a common clinical method of malocclusion. Studies have found that neurons in the sensorimotor cortex of the brain undergo adaptive remodeling in response to changes in oral behavior or occlusion.

OBJECTIVE

To explore whether orthodontic treatment could be sufficient to cause neuroplastic changes in the corticomotor excitability of the masseter muscle.

METHODS

Fifteen Angle Class II malocclusion patients who were receiving orthodontic treatment participated in the study. Cortical excitability was assessed by electromyographic activity changes evoked by transcranial magnetic stimulation. Four orthodontic time points were recorded, including baseline, day 1, day 7, and day 30. Motor evoked potentials (MEPs) were recorded in the masseter muscle and the first dorsal interosseous muscle (FDI) serving as a control. The data were analysed by stimulus-response curves and corticomotor mapping. Statistical analyses involved repeated measures analysis of variance, two-way ANOVA, and Tukey's post hoc tests.

RESULTS

Motor evoked potentials (MEPs) of the masseter muscle were significantly decreased during orthodontic treatment compared with those of the baseline (p < .001). MEPs of the masseter muscle were dependent on session and stimulus intensity (p < .001), whereas MEPs of FDI were only dependent on stimulus intensity (p = .091). Finally, Tukey's post hoc tests demonstrated that MEPs of the masseter muscle on days 1 and 7, with 70%-90% stimulus intensities, were higher than those of baseline values (p < .001).

CONCLUSIONS

The present study suggested that orthodontic treatment can lead to neuroplastic changes in the corticomotor control of the masseter muscle, which may add to our understanding of the adaptive response of subjects to changes of oral environment during the orthodontic treatment.

Schizophrenia-associated variation at ZNF804A correlates with altered experience-dependent dynamics of sleep slow waves and spindles in healthy young adults

The rs1344706 polymorphism in ZNF804A is robustly associated with schizophrenia and schizophrenia is, in turn, associated with abnormal non-rapid eye movement (NREM) sleep neurophysiology. To examine whether rs1344706 is associated with intermediate neurophysiological traits in the absence of disease, we assessed the relationship between genotype, sleep neurophysiology, and sleep-dependent memory consolidation in healthy participants. We recruited healthy adult males with no history of psychiatric disorder from the Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort. Participants were homozygous for either the schizophrenia-associated 'A' allele (N = 22) or the alternative 'C' allele (N = 18) at rs1344706. Actigraphy, polysomnography (PSG) and a motor sequence task (MST) were used to characterize daily activity patterns, sleep neurophysiology and sleep-dependent memory consolidation. Average MST learning and sleep-dependent performance improvements were similar across genotype groups, albeit more variable in the AA group. During sleep after learning, CC participants showed increased slow-wave (SW) and spindle amplitudes, plus augmented coupling of SW activity across recording electrodes. SW and spindles in those with the AA genotype were insensitive to learning, whilst SW coherence decreased following MST training. Accordingly, NREM neurophysiology robustly predicted the degree of overnight motor memory consolidation in CC carriers, but not in AA carriers. We describe evidence that rs1344706 polymorphism in ZNF804A is associated with changes in the coordinated neural network activity that supports offline information processing during sleep in a healthy population. These findings highlight the utility of sleep neurophysiology in mapping the impacts of schizophrenia-associated common genetic variants on neural circuit oscillations and function.

Practice schedule and testing per se affect children's transfer abilities in a grapho-motor task

Children's ability to transfer the gains of a motor experience, such as learning to write a letter, to novel conditions, such as cursive writing of the same letter, are affected by the way in which the learning experience is parsed. Parsing may have limitations because a short session may hamper the engagement of procedural memory consolidation processes. Here, we compared the effects of two practice schedules with the total amount of practice identical training provided in a single-session practice versus multi-session practice, wherein each session on its own was insufficient for generating long-term gains. A total of 40 7- and 8-year-old children practiced the production of a novel letter form by connecting dots, namely, the Invented Letter Task (ILT). Multiple ILT-related transfer tasks were assessed at 24 h post-training and again at 4-5 weeks post-training. Although by the end of training the single-session practice group outperformed the multi-session practice group in speed and accuracy, at 24 h post-training both groups showed comparable gains. However, after multi-session practice, children were as fast or faster and more accurate in the transfer tasks. By 4-5 weeks post-training, the multi-session practice group showed larger gains in the trained condition, a speed advantage in the transfer tasks, and a significant improvement on the transfer tasks. The results suggest that parsing training over several brief sessions may lead to long-term gains in children's grapho-motor skills. Moreover, multi-session practice protocols may contribute to the potential for transfer and to more effective learning from experiences such as transfer tasks.

Default mode and dorsal attention network involvement in visually guided motor sequence learning

Motor sequence learning (MSL) paradigms are often used to investigate the neural processes underlying the acquisition of complex motor skills. Behavioral and neuroimaging studies have indicated an early stage in which spatial learning is prominent and a late stage of automatized performance after multiple training periods. Functional magnetic resonance imaging (fMRI) studies yielded both decreased and increased activations of the sensorimotor and association areas. However, task-negative and task-positive intrinsic connectivity networks (ICNs), the default mode (DMN) and dorsal attention (DAN) networks involved in governing attention demands during various task conditions were not specifically addressed in most studies. In the present fMRI study, a visually guided MSL (VMSL) task was used for bringing roles of visuospatial and motor attention into foreground in order to investigate the role of attention-related ICNs in MSL. Seventeen healthy, right-handed participants completed training and test sessions of VMSL during fMRI on the 1st day. Then, after daily training for three consecutive days outside the scanner, they were re-tested during the 5th day's scanning session. When test session after early learning period was compared with training session, activation decrease was observed in the occipito-temporal fusiform cortex, while task-related suppression of DMN was reduced. Reduced deactivation after early learning was correlated with decreased error rates. After late learning stage we observed activation decreases in bilateral superior parietal lobules of task-positive DAN, dorsal precunei, and cerebellum. Reduced activity in left posterior parietal and right cerebellar regions were correlated with gains in speed, error rate, respectively. This dissociation in activity changes of DMN and DAN related areas suggests that DAN shows high contribution during both early and late MSL stages, possibly due to attention requirement for automatization of spatial and temporal aspects of motor sequence. In contrast, spatial learning occurring during early MSL stage was sufficient for releasing DMN resources.

Playing the piano with a robotic third thumb: assessing constraints of human augmentation

Contemporary robotics gives us mechatronic capabilities for augmenting human bodies with extra limbs. However, how our motor control capabilities pose limits on such augmentation is an open question. We developed a Supernumerary Robotic 3rd Thumbs (SR3T) with two degrees-of-freedom controlled by the user’s body to endow them with an extra contralateral thumb on the hand. We demonstrate that a pianist can learn to play the piano with 11 fingers within an hour. We then evaluate 6 naïve and 6 experienced piano players in their prior motor coordination and their capability in piano playing with the robotic augmentation. We show that individuals’ augmented performance with the SR3T could be explained by our new custom motor coordination assessment, the Human Augmentation Motor Coordination Assessment (HAMCA) performed pre-augmentation. Our work demonstrates how supernumerary robotics can augment humans in skilled tasks and that individual differences in their augmentation capability are explainable by their individual motor coordination abilities.

Anodal tDCS accelerates on-line learning of dart throwing

Transcranial direct current stimulation (tDCS) has been shown to enhance or block online learning of motor skills, depending on the current direction. However, most research on the use of tDCS has been limited to the study of relatively simple motor tasks. The purpose of the present study was to examine the influence of anodal (a-tDCS) and cathodal (c-tDCS) direct current stimulation on the online learning during a single session of dart throwing. Fifty-eight young adults were randomized to a-tDCS, c-tDCS, or SHAM groups and completed a pre-test block of dart throws, a 20-minute practice block of throws while receiving their stimulation condition, and a post-test block of dart throws. The results showed that a-tDCS accelerated the skill learning of dart throwing more than SHAM and c-tDCS conditions. The SHAM and c-tDCS conditions were not different. We conclude that a-tDCS may have a positive effect in a single training session which would be ideal in a recreational game environment where repeated practice is not common.

The neural underpinnings of motor learning in people with neurodegenerative diseases: A scoping review

Chronic progressive neurodegenerative diseases (NDD) cause mobility and cognitive impairments that disrupt quality of life. The learning of new motor skills, motor learning, is a critical component of rehabilitation efforts to counteract these chronic progressive impairments. In people with NDD, there are impairments in motor learning which appear to scale with the severity of impairment. Compensatory cortical activity plays a role in counteracting motor learning impairments in NDD. Yet, the functional and structural brain alterations associated with motor learning have not been synthesized in people with NDD. The purpose of this scoping review is to explore the neural alterations of motor learning in NDD. Thirty-five peer-reviewed original articles met the inclusion criteria. Participant demographics, motor learning results, and brain imaging results were extracted. Distinct motor learning associated compensatory processes were identified across NDD populations. Evidence from this review suggests the success of motor learning in NDD populations depends on the neural alterations and their interaction with motor learning networks, as well as the progression of disease.

The Impact of Verbal Encouragement and Repeating on the Measurement of Spirometry in Healthy Adult

Introduction  Vital Capacity (VC) is measured by spirometry. VC can differ according to weight, age, gender, race and height of the investigated person. Repetition of the same tasks has been proven to enhance adults' performance. Encouraging on some tasks have shown to result in a significant difference. Aim  This study aimed to examine if verbal encouragement and repetition of spirometry would make a difference in the results. Method This is a randomized clinical trial involving 136 healthy volunteers, randomly allocated to one of two groups: control and intervention groups. In both groups, VC was assessed as the baseline (VC1). VC was assessed again after ten days maximally (VC2). The third time of measuring VC was assessed again after ten days maximally (VC3). The verbal encouragement was provided only to the intervention group during iVC2 and iVC3, and only repeating was required from the control group in cVC2 and cVC3. Results and Conclusion  There was no significant difference in VC after the third trial in the control group compared to the baseline measurement (p-value= 0.836). On the other hand, verbal encouragement in the third trial had a significant difference in VC compared to the baseline measurement (p-value= 0.000).

Planning actions with a magnetic tool: how initial tool orientation and number of functional ends influence motor planning abilities in capuchin monkeys (Sapajus spp.)

The way in which animals grasp objects to perform subsequent action execution allows studying their anticipatory abilities. We examined whether 11 capuchin monkeys (Sapajus spp.) were able to prospectively grasp a magnetic dowel to use it as a tool to retrieve a baited metallic container from a plexiglas box placed in front of them. We investigated whether and how initial dowel orientation (horizontal vs vertical) affected grasping and using the dowel to retrieve the container in two testing conditions: (1) 2-FE condition in which the dowel had two functional magnetic ends; (2) 1-FE condition in which the dowel had only one functional magnetic end. In the 2-FE condition, capuchins had to take into account the initial dowel orientation since both ends were functional, whereas in the 1-FE condition capuchins had also to take into account the initial functional end position when grasping the dowel. Capuchins were trained to grasp the dowel to put one functional end in contact with the metallic container. However, they did not learn to associate the functional end of the 1-FE dowel to successful retrieval. Capuchins showed better anticipatory planning (1) in 2-FE than in 1-FE condition and (2) when the dowel was initially positioned on the horizontal plane than on the vertical one. Moreover, hand preferences affected planning in the 1-FE condition. Results were discussed within the frameworks of primates' abilities to use abstract cues and on their abilities to process functional features and spatial cues and to perform mental rotations.