Motor sequence learning and movement disorders

Neural mechanisms associated with sleep-dependent enhancement of motor learning after brain injury

This study aimed to examine the improvement in performance and functional magnetic resonance imaging correlates of motor learning after a daytime nap versus a period of resting wakefulness among individuals with traumatic brain injury. A sample of 32 individuals with traumatic brain injury was randomly assigned to a Sleep (N = 17) or Wake (N = 15) group after a period of training on a motor sequential learning task. A 45-min nap opportunity was provided for the Sleep group, while the Wake group watched a documentary for 45 min. Performance at the end of training was compared with their performance after the nap or wake intervention. Before and after the intervention, the motor sequential learning task was completed in the magnetic resonance imaging scanner to examine the relationship between change in performance and neural activation. Participants in the Sleep group showed significant gains from the end of training to after the intervention, whereas the Wake group did not. The functional magnetic resonance imaging results showed that relative to the Wake group, the Sleep group showed significantly decreased activation post-intervention in the anterior cingulate/paracingulate, cerebellum, cuneus/precuneus, and inferior parietal lobule including angular and supramarginal gyri. Importantly, across both groups, increased task performance at post-intervention was associated with decreased activation in the anterior cingulate/paracingulate and cerebellum. This study demonstrated the enhancing effect of a nap on motor learning performance in a sample of individuals with traumatic brain injury, with patterns of neural activation suggesting that the sequence was more automatized in the Sleep group. Strategic placement of a nap after an intense period of motor learning in the medical rehabilitation setting may have important implications for maximizing recovery after traumatic brain injury.

Update on Identification and Treatment of Infants and Toddlers With Suspected Childhood Apraxia of Speech

PURPOSE

The purpose of this tutorial is to (a) provide an updated review of the literature pertaining to proposed early features of childhood apraxia of speech (CAS), (b) discuss the findings of recent treatment studies of infants and toddlers with suspected CAS (sCAS), and (c) present evidence-based strategies and tools that can be used for the identification of and intervention for infants and toddlers with sCAS or at high risk for the disorder.

METHOD

Since Davis and Velleman's (2000) seminal work on assessment and intervention in infants and toddlers with sCAS, limited research has guided clinicians in the complex task of identifying and treating early speech motor difficulties prior to a definitive diagnosis of CAS. Following the structure of Davis and Velleman, we explore the proposed early characteristics of CAS with reference to contemporary research. Next, we describe the limited treatment studies that have investigated intervention for infants and toddlers at risk of or suspected of having CAS. Finally, we present practical suggestions for integrating this knowledge into clinical practice.

CONCLUSIONS

Many of the originally proposed correlates of CAS in infants and toddlers now have research supporting their presence. However, questions remain about the developmental trajectory of the disorder. Although limited in number and restricted by lack of experimental control, emerging treatment studies can help guide clinicians in providing appropriate intervention to infants and toddlers with sCAS who need not wait for a definitive diagnosis to initiate intervention.

A single exposure to 100% normo-baric oxygen therapy appears to improve sequence learning processes by increasing prefrontal cortex oxygen saturation

Previously, we showed that a normo-baric 100 % oxygen treatment (NbOxTr) enhances motor learning processes, e.g., visuomotor adaptation (VMA) and sequence learning (SL). However, this work was limited to behavioral outcomes and did not identify the physiological mechanistic underpinnings of these improvements. Here, we expand on this research to investigate the effects of a NbOxTr on the oxygen tissue saturation index (TSI) level of the prefrontal cortex (PFC) when performing a SL task and whether potential SL improvements relate to increased TSI levels in the PFC. Twenty four right-handed young, healthy adults were randomly assigned to a NbOxTr group (normo-baric 100 % oxygen, n = 12) or a control group (normal air, n = 12). They received their respective treatments via a nasal cannula during the experiment. Oxygen TSI levels of the right and left PFC were measured via near-infrared spectroscopy (NIRS) throughout different SL task phases (Baseline, Training, Testing). The NbOxTr increased the TSI of the PFC in the Training phase (p < 0.01) and positively affected SL retention in the Testing phase (p < 0.05). We also found a positive correlation between TSI changes in the right PFC during the gas treatment phase (3.4 % increase) and response time (RT) improvements in the SL task training and retention phase (all p < 0.05). Our results suggest that a simple NbOxTr increases the oxygenated hemoglobin availability in the PFC, which appears to mediate the retention of acquired SL improvements in healthy young adults. Future studies should examine treatment-related oxygenation changes in other brain areas involved and their relation to enhanced learning processes. Whether this NbOxTr improves SL in neurologically impaired populations should also be examined.

Anodal transcranial direct current stimulation does not enhance the effects of motor imagery training of a sequential finger-tapping task in young adults

When applied over the primary motor cortex (M1), anodal transcranial direct current stimulation (a-tDCS) could enhance the effects of a single motor imagery training (MIt) session on the learning of a sequential finger-tapping task (SFTT). This study aimed to investigate the effect of a-tDCS on the learning of an SFTT during multiple MIt sessions. Two groups of 16 healthy young adults participated in three consecutive MIt sessions over 3 days, followed by a retention test 1 week later. They received active or sham a-tDCS during a MIt session in which they mentally rehearsed an eight-item complex finger sequence with their left hand. Before and after each session, and during the retention test, they physically repeated the sequence as quickly and accurately as possible. Both groups (i) improved their performance during the first two sessions, showing online learning; (ii) stabilised the level they reached during all training sessions, reflecting offline consolidation; and (iii) maintained their performance level one week later, showing retention. However, no significant difference was found between the groups, regardless of the MSL stage. These results emphasise the importance of performing several MIt sessions to maximise performance gains, but they do not support the additional effects of a-tDCS.

Training-related changes in neural beta oscillations associated with implicit and explicit motor sequence learning

Many motor actions we perform have a sequential nature while learning a motor sequence involves both implicit and explicit processes. In this work, we developed a task design where participants concurrently learn an implicit and an explicit motor sequence across five training sessions, with EEG recordings at sessions 1 and 5. This intra-subject approach allowed us to study training-induced behavioral and neural changes specific to the explicit and implicit components. Based on previous reports of beta power modulations in sensorimotor networks related to sequence learning, we focused our analysis on beta oscillations at motor-cortical sites. On a behavioral level, substantial performance gains were evident early in learning in the explicit condition, plus slower performance gains across training sessions in both explicit and implicit sequence learning. Consistent with the behavioral trends, we observed a training-related increase in beta power in both sequence learning conditions, while the explicit condition displayed stronger beta power suppression during early learning. The initially stronger beta suppression and subsequent increase in beta power specific to the explicit component, correlated with enhanced behavioral performance, possibly reflecting higher cortical excitability. Our study suggests an involvement of motor-cortical beta oscillations in the explicit component of motor sequence learning.

Temporal and Spatial Accuracy of Reaching Movements do not Improve Off-line

Consolidation has been associated with performance gains without additional practice (i.e., off-line learning). However, the movement characteristics improving off-line remain poorly understood. To investigate this question, participants were trained to produce a sequence of planar reaching movements toward four different visual targets. The training session with feedback required them to learn the relative time of the movements, the total movement time and aim accurately at each target. The retention test was performed either 10-min or 24-h after. Results revealed that a 24-h consolidation interval did not result in better temporal or spatial accuracy. This finding suggests that off-line learning may be restricted to sequence production tasks in which the different segments must be regrouped ("chunked") together to accelerate their execution.

A simple 100% normobaric oxygen treatment can substantially enhance sequence learning processes

Motor learning processes are crucial for our everyday life, and improving skills by tailored interventions is of great clinical interest and value. Our previous work revealed a positive effect of normo-baric oxygen treatment on visuomotor adaptation. Here, we investigate whether it could positively affect sequence learning (SL) processes as well. Sixty-four healthy young adults were divided into a 100% oxygen treatment (NbOxTr; N = 32, M=20.7 ± 1.63 yrs.) and a normal air treatment (AirTr; N = 32, M=20.8 ± 0.95 yrs.) group. Participants performed a standardized SL task by pressing the spatial-compatible key on a keyboard according to four visual stimuli with two pre-determined 8-item sequences with different training depths. Following a baseline session (10 trials), both groups received a gas treatment (5 L/min, via nasal cannula) during the next training session (4 blocks, 45 trials each block), followed by a testing session (30 trials) without gas treatment. On day two, participants completed another 30 trials, similar to the first-day testing session, also without gas treatment. ANOVA revealed no significant group differences during baseline (p > 0.05) but a significantly faster response time (+45.5%) in the NbOxTr than AirTr group in the training session with gas treatment for all training depths (p < 0.05). The positive NbOxTr effect consolidated into the following testing session without gas treatment for deeply trained sequences (+17%; p < 0.05), and for all training depth on day-two testing (+45.2%; p < 0.05). Results suggest that the NbOxTr substantially improved participants' SL processing speed. Notably, improvements consolidated after an overnight sleep. The present work confirms a beneficial effect of a single, simple NbOxTr on fundamental motor learning processes. This treatment approach may provide promising implications for practice in neurological rehabilitation and other motor learning-related scenarios and should be further investigated in future research.

Implicit Motor Sequence Learning in People with Mild to Moderate Parkinson's Disease: Behavior and Related Brain Function

BACKGROUND

Deficits in motor learning could be an important explanation for the balance and gait impairments characteristic of people with Parkinson's disease (PD). Empirical studies often report that so-called implicit motor sequence learning is impaired in people with PD, but the results are inconclusive. Altered brain activity during implicit motor sequence learning has also been reported for people with PD in comparison to healthy individuals.

OBJECTIVE

To investigate implicit motor sequence learning and associated neural correlates in individuals with mild to moderate PD.

METHODS

Fifty-seven participants with PD and 34 healthy participants, all ≥60 years of age, performed the serial reaction time task (SRTT) during the acquisition of functional magnetic resonance imaging (fMRI) data. We analyzed the SRTT as a measure of implicit motor sequence learning in two complementary ways. We analyzed the task-induced fMRI data within regions of interest (ROIs) as well as functional connectivity between ROIs.

RESULTS

We found a significant group difference in SRTT performance indicating that the participants with PD had a somewhat lower level of implicit motor sequence learning than the healthy participants. Exploratory analyses suggested that impairments in implicit motor sequence learning for people with PD might be due to a lower learning rate. We did not find any significant group differences in the fMRI data.

CONCLUSION

Our exploratory finding of a lower implicit motor learning rate in PD could have important implications for how people with PD should practice new motor tasks and physical exercise. Future studies need to confirm this finding with hypothesis-driven analyses.

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.

Harnessing cognitive strategy use for functional problems and proposed underlying mechanisms in childhood-onset dystonia

BACKGROUND

There is a significant gap in knowledge about rehabilitation techniques and strategies that can help children and young people with hyperkinetic movement disorders (HMD) including dystonia to successfully perform daily activities and improve overall participation. A promising approach to support skill acquisition is the Cognitive Orientation to daily Occupational Performance (CO-OP) intervention. CO-OP uses cognitive strategies to help patients generate their own solutions to overcome self-identified problems encountered in everyday living.

PURPOSE

1. To identify and categorize strategies used by children with HMD to support skill acquisition during CO-OP; 2. To review the possible underlying mechanisms that might contribute to the cognitive strategies, in order to facilitate further studies for developing focused rehabilitation approaches.

METHODS

A secondary analysis was performed on video-recorded data from a previous study exploring the efficacy of CO-OP for childhood onset HMD, in which CO-OP therapy sessions were delivered by a single occupational therapist. For the purpose of this study, we reviewed a total of 40 randomly selected hours of video footage of CO-OP sessions delivered to six participants (age 6-19 years) over ten intervention sessions. An observational recording sheet was applied to identify systematically the participants' or therapist's verbalizations of cognitive strategies during the therapy. The strategies were classified into six categories in line with published literature.

RESULTS

Strategies used by HMD participants included distraction, externally focussed attention, internally focussed attention, emotion self-regulation, motor imagery and mental self-guidance. We postulate different underlying working mechanisms for these strategies, which have implications for the therapeutic management of children and young people with HMD including dystonia.

CONCLUSIONS

Cognitive strategy training can fundamentally change and improve motor performance. On-going work will address both the underlying neural mechanisms of therapeutic change and the mediators and moderators that influence how change unfolds.

Associations between resting-state functional connectivity changes and prolonged benefits of writing training in Parkinson's disease

BACKGROUND

Our earlier work showed that automaticity and retention of writing skills improved with intensive writing training in Parkinson's disease (PD). However, whether this training changed the resting-state networks in the brain and how these changes underlie retention of motor learning is currently unknown.

OBJECTIVE

To examine changes in resting-state functional connectivity (rs-FC) and their relation to behavioral changes immediately after writing training and at 6 week follow-up.

METHODS

Twenty-five PD patients underwent resting-state fMRI (ON medication) before and after 6 weeks writing training. Motor learning was evaluated with a dual task paradigm pre- and post-training and at follow-up. Next, pre-post within-network changes in rs-FC were identified by an independent component analysis. Significant clusters were used as seeds in ROI-to-ROI analyses and rs-FC changes were correlated with changes in behavioral performance over time.

RESULTS

Similar to our larger cohort findings, writing accuracy in single and dual task conditions improved post-training and this was maintained at follow-up. Connectivity within the dorsal attentional network (DAN) increased pre-post training, particularly with the right superior and middle temporal gyrus (rS/MTG). This cluster also proved more strongly connected to parietal and frontal areas and to cerebellar regions. Behavioral improvements from pre- to post-training and follow-up correlated with increased rs-FC between rS/MTG and the cerebellum.

CONCLUSIONS

Training-driven improvements in dual task writing led to functional reorganization within the DAN and increased connectivity with cerebellar areas. These changes were associated with the retention of writing gains and could signify task-specific neural changes or an inability to segregate neural networks.

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.

Sleep and homeostatic control of plasticity

Sleep homeostasis is a complex neurobiologic phenomenon involving a number of molecular pathways, neurotransmitter release, synaptic activity, and factors modulating neural networks. Sleep plasticity allows for homeostatic optimization of neural networks and the replay-based consolidation of specific circuits, especially important for cognition, behavior, and information processing. Furthermore, research is currently moving from an essentially brain-focused to a more comprehensive view involving other systems, such as the immune system, hormonal status, and metabolic pathways. When dysfunctional, these systems contribute to sleep loss and fragmentation as well as to sleep need. In this chapter, the implications of neural plasticity and sleep homeostasis for the diagnosis and treatment of some major sleep disorders, such as insomnia and sleep deprivation, obstructive sleep apnea syndrome, restless legs syndrome, REM sleep behavior disorder, and narcolepsy are discussed in detail with their therapeutical implications. This chapter highlights that sleep is necessary for the maintenance of an optimal brain function and is sensitive to both genetic background and environmental enrichment. Even in pathologic conditions, sleep acts as a resilient plastic state that consolidates prior information and prioritizes network activity for efficient brain functioning.

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.

Brain Activity and Functional Connectivity Patterns Associated With Fast and Slow Motor Sequence Learning in Late Middle Adulthood

The human brain undergoes structural and functional changes across the lifespan. The study of motor sequence learning in elderly subjects is of particularly interest since previous findings in young adults might not replicate during later stages of adulthood. The present functional magnetic resonance imaging (fMRI) study assessed the performance, brain activity and functional connectivity patterns associated with motor sequence learning in late middle adulthood. For this purpose, a total of 25 subjects were evaluated during early stages of learning [i.e., fast learning (FL)]. A subset of these subjects (n = 11) was evaluated after extensive practice of a motor sequence [i.e., slow learning (SL) phase]. As expected, late middle adults improved motor performance from FL to SL. Learning-related brain activity patterns replicated most of the findings reported previously in young subjects except for the lack of hippocampal activity during FL and the involvement of cerebellum during SL. Regarding functional connectivity, precuneus and sensorimotor lobule VI of the cerebellum showed a central role during improvement of novel motor performance. In the sample of subjects evaluated, connectivity between the posterior putamen and parietal and frontal regions was significantly decreased with aging during SL. This age-related connectivity pattern may reflect losses in network efficiency when approaching late adulthood. Altogether, these results may have important applications, for instance, in motor rehabilitation programs.

Altered neural oscillations during complex sequential movements in patients with Parkinson's disease

The sequelae of Parkinson's disease (PD) includes both motor- and cognitive-related symptoms. Although traditionally considered a subcortical disease, there is increasing evidence that PD has a major impact on cortical function as well. Prior studies have reported alterations in cortical neural function in patients with PD during movement, but to date such studies have not examined whether the complexity of multicomponent movements modulate these alterations. In this study, 23 patients with PD (medication "off" state) and 27 matched healthy controls performed simple and complex finger tapping sequences during magnetoencephalography (MEG), and the resulting MEG data were imaged to identify the cortical oscillatory dynamics serving motor performance. The patients with PD were significantly slower than controls at executing the sequences overall, and both groups took longer to complete the complex sequences than the simple. In terms of neural differences, patients also exhibited weaker beta complexity-related effects in the right medial frontal gyrus and weaker complexity-related alpha activity in the right posterior and inferior parietal lobules, suggesting impaired motor sequence execution. Characterizing the cortical pathophysiology of PD could inform current and future therapeutic interventions that address both motor and cognitive symptoms.

Day versus night consolidation of implicit sequence learning using manual and oculomotor activation versions of the serial reaction time task: reaction time and anticipation measures

This study presents two experiments that explored consolidation of implicit sequence learning based on two dependent variables-reaction time (RT) and correct anticipations to clarify the role of sleep, and whether the manual component is necessary for consolidation processes. Experiment 1 (n = 37) explored the performance of adults using an ocular variant of the serial reaction time task (O-SRT) with manual activation (MA), and Experiment 2 (n = 37) used the ocular activation (OA) version of the task. Each experiment consisted of a Day and a Night group that performed two sessions of the O-SRT with an intervening 12-h offline period (morning/evening in Day group, evening/following morning in Night group). Night offline had an advantage only when manual response was required and when correct anticipations (i.e., accuracy) but not RT (i.e., speed) were measured. We associated this finding with the dual-learning processes required in the MA O-SRT that led to increased sequence specific learning overnight. When using the OA O-SRT, both groups demonstrated similar rates after offline in RT and correct anticipations. We interpreted this finding to reflect stabilization, which confirmed our hypothesis. As expected, all the groups demonstrated reduced performance when another sequence was introduced, thus reflecting sequence-specific learning. This study used a powerful procedure that allows measurement of implicit sequence learning in several ways: by evaluating two different measures (RT, correct anticipations) and by isolating different aspects of the task (i.e., with/without the manual learning component, more/less general skill learning), which are known to affect learning and consolidation.

Explicit motor sequence learning after stroke: a neuropsychological study

Motor learning interacts with and shapes experience-dependent cerebral plasticity. In stroke patients with paresis of the upper limb, motor recovery was proposed to reflect a process of re-learning the lost/impaired skill, which interacts with rehabilitation. However, to what extent stroke patients with hemiparesis may retain the ability of learning with their affected limb remains an unsolved issue, that was addressed by this study. Nineteen patients, with a cerebrovascular lesion affecting the right or the left hemisphere, underwent an explicit motor learning task (finger tapping task, FTT), which was performed with the paretic hand. Eighteen age-matched healthy participants served as controls. Motor performance was assessed during the learning phase (i.e., online learning), as well as immediately at the end of practice, and after 90 min and 24 h (i.e., retention). Results show that overall, as compared to the control group, stroke patients, regardless of the side (left/right) of the hemispheric lesion, do not show a reliable practice-dependent improvement; consequently, no retention could be detected in the long-term (after 90 min and 24 h). The motor learning impairment was associated with subcortical damage, predominantly affecting the basal ganglia; conversely, it was not associated with age, time elapsed from stroke, severity of upper-limb motor and sensory deficits, and the general neurological condition. This evidence expands our understanding regarding the potential of post-stroke motor recovery through motor practice, suggesting a potential key role of basal ganglia, not only in implicit motor learning as previously pointed out, but also in explicit finger tapping motor tasks.

The Differential Effects of Auditory and Visual Stimuli on Learning, Retention and Reactivation of a Perceptual-Motor Temporal Sequence in Children With Developmental Coordination Disorder

This study investigates the procedural learning, retention, and reactivation of temporal sensorimotor sequences in children with and without developmental coordination disorder (DCD). Twenty typically-developing (TD) children and 12 children with DCD took part in this study. The children were required to tap on a keyboard, synchronizing with auditory or visual stimuli presented as an isochronous temporal sequence, and practice non-isochronous temporal sequences to memorize them. Immediate and delayed retention of the audio-motor and visuo-motor non-isochronous sequences were tested by removing auditory or visual stimuli immediately after practice and after a delay of 2 h. A reactivation test involved reintroducing the auditory and visual stimuli after the delayed recall. Data were computed via circular analyses to obtain asynchrony, the stability of synchronization and errors (i.e., the number of supplementary taps). Firstly, an overall deficit in synchronization with both auditory and visual isochronous stimuli was observed in DCD children compared to TD children. During practice, further improvements (decrease in asynchrony and increase in stability) were found for the audio-motor non-isochronous sequence compared to the visuo-motor non-isochronous sequence in both TD children and children with DCD. However, a drastic increase in errors occurred in children with DCD during immediate retention as soon as the auditory stimuli were removed. Reintroducing auditory stimuli decreased errors in the audio-motor sequence for children with DCD. Such changes were not seen for the visuo-motor non-isochronous sequence, which was equally learned, retained and reactivated in DCD and TD children. All these results suggest that TD children benefit from both auditory and visual stimuli to memorize the sequence, whereas children with DCD seem to present a deficit in integrating an audio-motor sequence in their memory. The immediate effect of reactivation suggests a specific dependency on auditory information in DCD. Contrary to the audio-motor sequence, the visuo-motor sequence was both learned and retained in children with DCD. This suggests that visual stimuli could be the best information for memorizing a temporal sequence in DCD. All these results are discussed in terms of a specific audio-motor coupling deficit in DCD.

Exploring the Neural Structures Underlying the Procedural Memory Network as Predictors of Language Ability in Children and Adolescents With Autism Spectrum Disorder and Attention Deficit Hyperactivity Disorder

Introduction: There is significant overlap in the type of structural language impairments exhibited by children with autism spectrum disorder (ASD) and children with attention deficit hyperactivity disorder (ADHD). This similarity suggests that the cognitive impairment(s) contributing to the structural language deficits in ASD and ADHD may be shared. Previous studies have speculated that procedural memory deficits may be the shared cognitive impairment. The procedural deficit hypothesis (PDH) argues that language deficits can be explained by differences in the neural structures underlying the procedural memory network. This hypothesis is based on the premise that the neural structures comprising the procedural network support language learning. In this study, we aimed to test the PDH in children with ASD, ADHD, and typical development (TD).

Methods: One hundred and sixty-three participants (ages 10–21): 91 with ASD, 26 with ADHD, and 46 with TD, completed standardized measures of cognitive and language ability as well as structural magnetic resonance imaging. We compared the structural language abilities, the neural structures underlying the procedural memory network, and the relationship between structural language and neural structure across diagnostic groups.

Results: Our analyses revealed that while the structural language abilities differed across ASD, ADHD, and TD groups, the thickness, area, and volume of the structures supporting the procedural memory network were not significantly different between diagnostic groups. Also, several neural structures were associated with structural language abilities across diagnostic groups. Only two of these structures, the inferior frontal gyrus, and the left superior parietal gyrus, are known to be linked to the procedural memory network.

Conclusions: The inferior frontal gyrus and the left superior parietal gyrus, have well-established roles in language learning independent of their role as part of the procedural memory system. Other structures such as the caudate and cerebellum, with critical roles in the procedural memory network, were not associated with structural language abilities across diagnostic groups. It is unclear whether the procedural memory network plays a fundamental role in language learning in ASD, ADHD, and TD.

Procedural Sequence Learning in Attention Deficit Hyperactivity Disorder: A Meta-Analysis

Previous literature proposes that the motor deficits in Attention Deficit Hyperactivity Disorder (ADHD) may be attributed to impairments of the procedural memory network, a long-term memory system involved in sensorimotor and cognitive skill development. A handful of studies have explored procedural sequence learning in ADHD, but findings have been inconsistent. A meta-analysis was conducted to begin to establish whether procedural sequence learning deficits exist in ADHD. The results of seven studies comprising 213 participants with ADHD and 257 participants with typical development (TD) generated an average standardized mean difference of 0.02 (CI95 -0.35, 0.39) that was not significant. Heterogeneity was significant across studies and could be partially attributed to the age of participants. We argue that procedural sequence learning appears to be preserved in ADHD and discuss potential explanations for and against this finding.

Acquisition and consolidation of sequential footstep movements with physical and motor imagery practice

Sleep-dependent performance enhancement has been consistently reported after explicit sequential finger learning, even using motor imagery practice (MIP), but whether similar sleep benefits occur after explicit sequential gross motor learning with the lower limbs has been addressed less often. Here, we investigated both acquisition and consolidation processes in an innovative sequential footstep task performed either physically or mentally. Forty-eight healthy young participants were tested before and after physical practice (PP) or MIP on the footstep task, following either a night of sleep (PPsleep and MIPsleep groups) or an equivalent daytime period (PPday and MIPday groups). Results showed that all groups improved motor performance following the acquisition session, albeit the magnitude of enhancement in the MIP groups remained lower relative to the PP groups. Importantly, only the MIPsleep group further improved performance after a night of sleep, while the other groups stabilized their performance after consolidation. Together, these findings demonstrate a sleep-dependent gain in performance after MIP in a sequential motor task with the lower limbs but not after PP. Overall, the present study is of particular importance in the context of motor learning and functional rehabilitation.

Discrete finger sequences are widely represented in human striatum

Research in primates and rodents ascribes the striatum a critical role in integrating elementary movements into unitary action sequences through reinforcement-based learning. Yet it remains to be shown whether the human striatum represents action sequence-specific information. Young right-handed volunteers underwent functional magnetic resonance imaging while they performed four discrete finger sequences with their right hand, consisting of five button presses. Specific finger sequences could be discriminated based on the distributed activity patterns in left and right striatum, but not by average differences in single-voxel activity. Multiple bilateral clusters in putamen and caudate nucleus belonging to motor, associative, parietal and limbic territories contributed to classification sensitivity. The results show that individual finger movement sequences are widely represented in human striatum, supporting functional integration rather than segregation. The findings are compatible with the idea that the basal ganglia simultaneously integrate motor, associative and limbic aspects in the control of complex overlearned behaviour.

Dopamine replacement improves motor learning of an upper extremity task in people with Parkinson disease

BACKGROUND

Dopamine replacement medication has positive effects on existing motor skills for people with Parkinson disease (PD), but may have detrimental effects on the learning of motor skills necessary for effective rehabilitation according to the dopamine overdose hypothesis.

OBJECTIVES

This study aimed to determine whether dopamine replacement medication (i.e. levodopa) affects: learning of a novel upper extremity task, decrements in skill following withdrawal of practice, the rate of learning, and the transfer of movement skill to untrained upper extremity tasks compared to training "off" medication, in people with PD.

METHODS

Participants with mild-moderate PD (Hoehn and Yahr stage 2) were randomized to train "on" (n = 12) or "off" (n = 11) levodopa medication. Participants practiced 10 blocks of five trials of a functional motor task with their non-dominant upper extremity over three consecutive days (acquisition period), followed by a single block of five trials two and nine days later. Participants were also assessed "on" levodopa with two transfer tasks (the nine-hole peg test and a functional dexterity task) prior to any practice and nine days after the end of the acquisition period.

RESULTS

Participants who practiced "on" levodopa medication learned the upper extremity task to a greater extent that those who practiced "off" medication, as determined by retained performance two days after practice. Skill decrement and skill transfer were not significantly different between groups. Rate of learning was unable to be modelled in this sample.

CONCLUSIONS

Levodopa medication improved the learning of an upper extremity task in people with mild-moderate PD.

The importance of different learning stages for motor sequence learning after stroke

The task of learning predefined sequences of interrelated motor actions is of everyday importance and has also strong clinical importance for regaining motor function after brain lesions. A solid understanding of sequence learning in stroke patients can help clinicians to optimize and individualize rehabilitation strategies. Moreover, to investigate the impact of a focal lesion on the ability to successfully perform motor sequence learning can enhance our comprehension of the underlying physiological principles of motor sequence learning. In this article, we will first provide an overview of current concepts related to motor sequence learning in healthy subjects with focus on the involved brain areas and their assumed functions according to the temporal stage model. Subsequently, we will consider the question of what we can learn from studies investigating motor sequence learning in stroke patients. We will first focus on the implications of lesion location. Then, we will analyze whether distinct lesion locations affect specific learning stages. Finally, we will discuss the implications for clinical rehabilitation and suggest directions for further research.

Acquisition and consolidation of implicit motor learning with physical and mental practice across multiple days of anodal tDCS

BACKGROUND

Acquisition and consolidation of a new motor skill occurs gradually over long time span. Motor imagery (MI) and brain stimulation have been showed as beneficial approaches that boost motor learning, but little is known about the extent of their combined effects.

OBJECTIVE

Here, we aimed to investigate, for the first time, whether delivering multiple sessions of transcranial direct current stimulation (tDCS) over primary motor cortex during physical and MI practice might improve implicit motor sequence learning in a young population.

METHODS

Participants practiced a serial reaction time task (SRTT) either physically or through MI, and concomitantly received either an anodal (excitatory) or sham stimulation over the primary motor cortex during three successive days. The effect of anodal tDCS on the general motor skill and sequence specific learning were assessed on both acquisition (within-day) and consolidation (between-day) processes. We further compared the magnitude of motor learning reached after a single and three daily sessions of tDCS.

RESULTS

The main finding showed that anodal tDCS boosted MI practice, but not physical practice, during the first acquisition session. A second major result showed that compared to sham stimulation, multiple daily session of anodal tDCS, for both types of practice, resulted in greater implicit motor sequence learning rather than a single session of stimulation.

CONCLUSIONS

The present study is of particular importance in the context of rehabilitation, where we postulate that scheduling mental training when patients are not able to perform physical movement might beneficiate from concomitant and consecutive brain stimulation sessions over M₁ to promote functional recovery.

Impaired Motor Skill Acquisition Using Mirror Visual Feedback Improved by Transcranial Direct Current Stimulation (tDCS) in Patients With Parkinson's Disease

Recent non-invasive brain stimulation techniques in combination with motor training can enhance neuroplasticity and learning. It is reasonable to assume that such neuroplasticity-based interventions constitute a useful rehabilitative tool for patients with Parkinson's Disease (PD). Regarding motor skill training, many kinds of tasks that do not involve real motor movements have been applied to PD patients. The purpose of this study is to elucidate whether motor skill training using mirror visual feedback (MVF) is useful to patients with PD in order to improve untrained hand performance dependent on the time course of training; and whether MVF combined with anodal transcranial direct current stimulation (tDCS) over primary motor cortex (M1) causes an additional effect based on increased motor cortical excitability. Eighteen right-handed patients with PD in the off-medication state and 10 age-matched healthy subjects (HS) performed four sessions of right-hand ball rotation using MVF (intervention) on two separate days, 1 week apart (day 1 and day 2). HS subjects received only sham stimulation. The intervention included four sessions of motor-skill training using MVF for 20 min comprised of four sets of training for 30 s each. PD patients were randomly divided into two intervention groups without or with anodal tDCS over the right M1 contralateral to the untrained hand. As the behavior evaluation, the number of ball rotations of the left hand was counted before (pre) and immediately after (post) intervention on both days (pre day 1, post day 1, pre day 2, and post day 2). Motor evoked potential (MEP), input-output function, and cortical silent period were recorded to evaluate the motor cortical excitatory and inhibitory system in M1 pre day 1 and post day 2. The number of ball rotations of the left hand and the facilitation of MEP by intervention were significantly impaired in patients with PD compared to HS. In contrast, if anodal tDCS was applied to right M1 of patients with PD, the number of ball rotations in accordance with I-O function at 150% intensity was significantly increased after day 1 and retained until day 2. This finding may help provide a new strategy for neurorehabilitation improving task-specific motor memory without real motor movements in PD.

Disentangling motor planning and motor execution in unmedicated de novo Parkinson's disease patients: An fMRI study

Many studies have used functional magnetic resonance imaging to unravel the neuronal underpinnings of motor system abnormalities in Parkinson's disease, indicating functional inhibition at the level of basal ganglia-thalamo-cortical motor networks. The study aim was to extend the characterization of functional motor changes in Parkinson's Disease by dissociating between two phases of action (i.e. motor planning and motor execution) during an automated unilateral finger movement sequence with the left and right hand, separately. In essence, we wished to identify neuronal dysfunction and potential neuronal compensation before (planning) and during (execution) automated sequential motor behavior in unmedicated early stage Parkinson's Disease patients. Twenty-two Parkinson's Disease patients (14 males; 53 ± 11 years; Hoehn and Yahr score 1.4 ± 0.6; UPDRS (part 3) motor score 16 ± 6) and 22 healthy controls (14 males; 49 ± 12 years) performed a pre-learnt four finger sequence (index, ring, middle and little finger, in order), either self-initiated (FREE) or externally triggered (REACT), within an 8-second time window. Findings were most pronounced during FREE with the clinically most affected side, where motor execution revealed significant underactivity of contralateral primary motor cortex, contralateral posterior putamen (sensorimotor territory), ipsilateral anterior cerebellum / cerebellar vermis, along with underactivity in supplementary motor area (based on ROI analyses only), corroborating previous findings in Parkinson's Disease. During motor planning, Parkinson's Disease patients showed a significant relative overactivity in dorsolateral prefrontal cortex (DLPFC), suggesting a compensatory overactivity. To a variable extent this relative overactivity in the DLPFC went along with a relative overactivity in the precuneus and the ipsilateral anterior cerebellum/cerebellar vermis Our study illustrates that a refined view of disturbances in motor function and compensatory processes can be gained from experimental designs that try to dissociate motor planning from motor execution, emphasizing that compensatory mechanisms are triggered in Parkinson's Disease when voluntary movements are conceptualized for action.

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Dissociated activations in early stage PD for motor planning and motor execution

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PD patients show frontal-parietal network compensation during self-initiated movement.

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Compensation for an impaired basal ganglia-premotor circuit occurs during planning.

Effect of spinal tap test on the performance of sit-to-stand, walking, and turning in patients with idiopathic normal pressure hydrocephalus

The aim of the study was to investigate the effect of the spinal tap test on sit-to-stand (STS), walking, and turning and to determine the relationship among the outcome measures of STS, walking, and turning in patients with iNPH. Twenty-seven patients with clinical symptoms of iNPH were objectively examined for STS, walking, and turning by the Force Distribution Measurement (FDM) platform connected with a video camera. Assessments were performed at before and 24 hours after spinal tap. Motor abilities were assessed by the STS time, time of walking over 3 meters, and time and number of steps when turning over 180 degrees. Significant improvements were found in the STS time (p = 0.046), walking time (p = 0.048), and turning step (p = 0.001). In addition, turning time was improved but not statistically significant (p = 0.064). Significant relationships were found among all outcome measures (p < 0.001). The relationship among these outcome measures indicated that the individuals had similar ability levels to perform different activities. This may serve as a new choice of outcome measures to evaluate the effect of intervention in different severity levels of patients with iNPH.

A randomized controlled study of whether setting specific goals improves the effectiveness of therapy in people with Parkinson's disease

OBJECTIVE:

To evaluate the effects of an intervention based on a specific set of goals on goal attainment, manual dexterity, hand grip strength and finger prehension force compared to a standardized approach in patients with Parkinson's disease.

DESIGN:

Randomized controlled trial.

SETTING:

Home-based.

PARTICIPANTS:

Fifty patients with a clinical diagnosis of Parkinson's disease acknowledging impaired manual ability were randomized into two groups.

INTERVENTIONS:

Patients in the experimental group ( n = 25) were included in an intervention focused on task components that involved goals proposed by participants. Patients in the control group ( n = 25) received a standard intervention focused on impairments in range of motion, grasp and manipulation. Home condition and duration (four weeks, twice a week) were similar in both groups.

MAIN OUTCOME MEASURES:

The primary outcome measure was goal achievement assessed with the Goal Attainment Scaling. Secondary outcomes were manual dexterity evaluated with the Purdue Pegboard Test and hand grip strength and finger prehension force assessed using a dynamometer.

RESULTS:

After four weeks, significant between-group improvement in goal attainment was observed in the experimental group (change 17.36 ± 7.48 vs. 4.03 ± 6.43, P < 0.001). Compared to the control group, the experimental group also showed a significant improvement ( P < 0.05) in manual dexterity (postintervention values in the most affected arm 10.55 ± 1.95 vs. 7.33 ± 3.63 pins, P < 0.001) and finger prehension force (postintervention values in the most affected arm 8.03 ± 1.93 vs. 6.31 ± 1.85 kg, P = 0.010).

CONCLUSIONS:

Targeting therapy toward specific goals leads to greater changes in arm function than a standardized approach in people with Parkinson's disease.

Fluency adaptation in speakers with Parkinson disease: a motor learning perspective

PURPOSE

Fluency adaptation is characterised by a reduction in stuttering-like behaviours over successive readings of the same speech material and is an effect that is typically observed in developmental stuttering. Prominent theories suggest that short-term motor learning associated with practice explain, in part, fluency adaptation. The current investigation examined the fluency adaptation effect in a group of speakers with Parkinson disease (PD) who exhibited stuttering-like disfluencies.

METHOD

Individuals with PD (n = 21) and neurologically healthy controls (n = 19) read a passage five times. Per cent syllables stuttered was measured and calculated for each reading passage.

RESULT

Participants in the PD group exhibited significantly more stuttering-like disfluencies than control speakers. Twelve individuals in the PD group exhibited at least three per cent syllable stuttered on at least one reading. Statistical trends revealed that the subgroup of individuals with PD who stuttered exhibited a significant reduction in stuttering moments over the five successive readings.

CONCLUSION

A significant fluency adaptation effect was observed for the group of speakers with PD who exhibited stuttering-like disfluencies. Results of the current study are discussed within the framework of the motor learning hypothesis of fluency adaptation.

A Single Bout of Aerobic Exercise Improves Motor Skill Consolidation in Parkinson's Disease

Background: Motor learning is impaired in Parkinson’s disease (PD), with patients demonstrating deficits in skill acquisition (online learning) and consolidation (offline learning) compared to healthy adults of similar age. Recent studies in young adults suggest that single bouts of aerobic exercise (AEX), performed in close temporal proximity to practicing a new motor task, may facilitate motor skill learning. Thus, we aimed at investigating the effects of a single bout of aerobic cycling on online and offline learning in PD patients.

Methods: 17 PD patients (Hoehn and Yahr 1 – 2.5, age: 64.4 ± 6.2) participated in this crossover study. Immediately prior to practicing a novel balance task, patients either performed 30 min of (i) moderate intensity (60–70% VO_2max) aerobic cycling, or (ii) seated rest (order counterbalanced). The task required patients to stabilize a balance platform (stabilometer) in a horizontal position for 30 s. For each experimental condition, patients performed 15 acquisition trials, followed by a retention test 24 h later. We calculated time in balance (platform within ± 5° from horizontal) for each trial, and analyzed within- and between-subjects differences in skill acquisition (online learning) and skill retention (offline learning) using mixed repeated-measures ANOVA.

Results: We found that the exercise bout had no effect on performance level or online gains during acquisition, despite affecting the time course of skill improvements (larger initial and reduced late skill gains). Aerobic cycling significantly improved offline learning, as reflected by larger 24-h skill retention compared to the rest condition.

Conclusion: Our results suggest that a single bout of moderate-intensity AEX is effective in improving motor skill consolidation in PD patients. Thus, acute exercise may represent an effective strategy to enhance motor memory formation in this population. More work is necessary to understand the underlying mechanisms, the optimal scheduling of exercise, and the applicability to other motor tasks. Further, the potential for patients in later disease stages need to be investigated. The study was a priori registered at ClinicalTrials.gov (NCT03245216).

The significance of brain oscillations in motor sequence learning: Insights from Parkinson's disease

Motor sequence learning plays a pivotal role in various everyday activities. Motor-cortical beta oscillations have been suggested to be involved in this type of learning. In Parkinson's disease (PD), oscillatory activity within cortico-basal-ganglia circuits is altered. Pathologically increased beta oscillations have received particular attention as they may be associated with motor symptoms such as akinesia. In the present magnetoencephalography (MEG) study, we investigated PD patients and healthy controls (HC) during implicit motor sequence learning with the aim to shed light on the relation between changes of cortical brain oscillations and motor learning in PD with a particular focus on beta power. To this end, 20 PD patients (ON medication) and 20 age- and sex-matched HC were trained on a serial reaction time task while neuromagnetic activity was recorded using a 306-channel whole-head MEG system. PD patients showed reduced motor sequence acquisition and were more susceptible to interference by random trials after training on the task as compared to HC. Behavioral differences were paralleled by changes at the neurophysiological level. Diminished sequence acquisition was paralleled by less training-related beta power suppression in motor-cortical areas in PD patients as compared to HC. In addition, PD patients exhibited reduced training-related theta activity in motor-cortical areas paralleling susceptibility to interference. The results support the hypothesis that the acquisition of a new motor sequence relies on suppression of motor-cortical beta oscillations, while motor-cortical theta activity might be related to stabilization of the learned sequence as indicated by reduced susceptibility to interference. Both processes appear to be impaired in PD.

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Motor sequence acquisition and susceptibility to interference is altered in PD.

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Diminished sequence acquisition is paralleled by less beta power suppression in PD.

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Higher susceptibility to interference is accompanied by less theta activity in PD.

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The data imply the relevance of beta and theta activity to motor sequence learning.

Anodal Transcranial Direct Current Stimulation (tDCS) Over the Right Primary Motor Cortex (M1) Impairs Implicit Motor Sequence Learning of the Ipsilateral Hand

Motor sequence learning is associated with the activation of bilateral primary motor cortices (M1). While previous data support the hypothesis that the contralateral M1 is causally involved in the acquisition as well as early consolidation of a motor sequence, the functional significance of the ipsilateral M1 has yet to be solved. Transcranial direct current stimulation (tDCS) allows the non-invasive modulation of cortical excitability. Anodal tDCS applied to the left M1 has been shown to facilitate implicit motor sequence learning of the right hand most likely due to increased excitability. The present study aims at characterizing the functional contribution of the ipsilateral (right) M1 on implicit motor sequence learning of the right hand. To this end, 24 healthy, right-handed subjects received anodal and sham tDCS to the right M1 in a counterbalanced order. Stimulation started 8 min prior to training on a variant of the serial reaction time task (SRTT) with the right hand and persists over the entire training period. The SRTT comprised a fixed eight-digit sequence. A random pattern served as control condition. Reaction times were assessed before and at the end of the acquisition (EoA) immediately after training on the SRTT. The analysis revealed significantly faster reaction times of both hands independent of tDCS condition in sequential trials. However, the gain of reaction times was significantly smaller following anodal as compared to sham tDCS. The data suggest that anodal tDCS applied to the right M1 impairs implicit motor sequence learning of both hands. The underlying mechanism likely involves alterations of the interaction between bilateral M1.

Preservation of explicit learning of visuomotor sequences during Parkinson's disease progression

While motor learning approaches are effective in rehabilitating Parkinson’s disease (PD) patients, many studies reported deficits in sequential motor learning in these patients. We hypothesised that preserved explicit learning of visuomotor sequences in PD patients contributed to the effectiveness of motor learning approaches. However, there are very few studies analysing explicit learning of visuomotor sequences during the progression of PD. We investigated this phenomenon in 23 patients with moderate to severe PD (Hoehn–Yahr stages II-IV) and 17 age-matched controls using sequential button-press tasks (2 × 5 task). We found (1) no significant differences in numbers of errors in the 2 × 5 task among control and PD groups. (2) There was a significant difference in response times while exploring correct sequences (ERT) among control and PD groups; ERTs in stage-IV patients tended to be longer than those of control and stage-II groups. (3) All four groups significantly improved their performance (i.e., reduced ERTs in the 2 × 5 task) with sequence repetition, although stage-III:IV patients were slower. Thus, even patients with severe PD can learn visual sequences and can translate them into visuomotor sequences (explicit visuomotor sequence learning), albeit slower than controls, providing evidence for effective motor learning approaches during rehabilitation of patients with advanced PD.

Basal ganglia and beyond: The interplay between motor and cognitive aspects in Parkinson's disease rehabilitation

Parkinson's disease (PD) is characterized by motor and cognitive dysfunctions, affecting the motor behaviour. We summarize evidence that the interplay between motor and cognitive approaches is crucial in PD rehabilitation. Rehabilitation is complementary to pharmacological therapy and effective in reducing the PD disturbances, probably acting by inducing neuroplastic effects. The motor behaviour results from a complex integration between cortical and subcortical areas, underlying the motor, cognitive and motivational aspects of movement. The close interplay amongst these areas makes possible to learn, control and express habitual-automatic actions, which are dysfunctional in PD. The physiopathology of PD could be considered the base for the development of effective rehabilitation treatments. As the volitional action control is spared in early-medium stages of disease, rehabilitative approaches engaging cognition permit to achieve motor benefits and appear to be the most effective for PD. We will point out data supporting the relevance of targeting both motor and cognitive aspects in PD rehabilitation. Finally, we will discuss the role of cognitive engagement in motor rehabilitation for PD.

Common neural basis of motor sequence learning and word recognition and its relation with individual differences in reading skill

To investigate the neural basis of a common statistical learning mechanism involved in motor sequence learning and decoding, we recorded same participants' brain activation in a serial reaction time (SRT) and word reading task using functional magnetic resonance imaging. In the SRT, a manual response was made depending on the location of a visual cue, and the order of the locations was either fixed or random. In the word reading task, visual words were passively presented. Compared to less skilled readers, more skilled readers showed greater differences in activation in the inferior frontal gyrus pars triangularis (IFGpTr) and the insula between the ordered and random condition in the SRT task and greater activation in those regions in the word reading task. It suggests that extraction of statistically predictable patterns in the IFGpTr and insula contributes to both motor sequence learning and orthographic learning, and therefore predicts individual differences in decoding skill.

Draft genome assembly of the Bengalese finch, Lonchura striata domestica, a model for motor skill variability and learning

Background

Vocal learning in songbirds has emerged as a powerful model for sensorimotor learning. Neurobehavioral studies of Bengalese finch (Lonchura striata domestica) song, naturally more variable and plastic than songs of other finch species, have demonstrated the importance of behavioral variability for initial learning, maintenance, and plasticity of vocalizations. However, the molecular and genetic underpinnings of this variability and the learning it supports are poorly understood.

Findings

To establish a platform for the molecular analysis of behavioral variability and plasticity, we generated an initial draft assembly of the Bengalese finch genome from a single male animal to 151× coverage and an N50 of 3.0 MB. Furthermore, we developed an initial set of gene models using RNA-seq data from 8 samples that comprise liver, muscle, cerebellum, brainstem/midbrain, and forebrain tissue from juvenile and adult Bengalese finches of both sexes.

Conclusions

We provide a draft Bengalese finch genome and gene annotation to facilitate the study of the molecular-genetic influences on behavioral variability and the process of vocal learning. These data will directly support many avenues for the identification of genes involved in learning, including differential expression analysis, comparative genomic analysis (through comparison to existing avian genome assemblies), and derivation of genetic maps for linkage analysis. Bengalese finch gene models and sequences will be essential for subsequent manipulation (molecular or genetic) of genes and gene products, enabling novel mechanistic investigations into the role of variability in learned behavior.

Asymmetries in initiation of aiming movements in schizophrenia

Several studies have reported motor symptoms in schizophrenia (SCZ), in some cases describing asymmetries in their manifestation. To date, biases were mainly reported for sequential movements, and the hypothesis was raised of a dopamine-related hemispheric imbalance. Aim of this research is to better characterize asymmetries in movement initiation in SCZ by exploring single actions. Fourteen SCZ patients and fourteen healthy subjects were recruited. On a trial-by-trial basis, participants were instructed to reach for one of eight possible targets. Measures of movement initiation and execution were collected. Starting point, target and moving limb were systematically varied to check for asymmetric responses. Results showed that SCZ patients, besides being overall slower than controls, additionally presented with a bias affecting both the moving hand and the side from which movements were initiated. This finding is discussed in relation to hemispheric lateralization in motor control.

Enrichment Effects of Gestures and Pictures on Abstract Words in a Second Language

Laboratory research has demonstrated that multisensory enrichment promotes verbal learning in a foreign language (L2). Enrichment can be done in various ways, e.g., by adding a picture that illustrates the L2 word’s meaning or by the learner performing a gesture to the word (enactment). Most studies have tested enrichment on concrete but not on abstract words. Unlike concrete words, the representation of abstract words is deprived of sensory-motor features. This has been addressed as one of the reasons why abstract words are difficult to remember. Here, we ask whether a brief enrichment training by means of pictures and by self-performed gestures also enhances the memorability of abstract words in L2. Further, we explore which of these two enrichment strategies is more effective. Twenty young adults learned 30 novel abstract words in L2 according to three encoding conditions: (1) reading, (2) reading and pairing the novel word to a picture, and (3) reading and enacting the word by means of a gesture. We measured memory performance in free and cued recall tests, as well as in a visual recognition task. Words encoded with gestures were better remembered in the free recall in the native language (L1). When recognizing the novel words, participants made less errors for words encoded with gestures compared to words encoded with pictures. The reaction times in the recognition task did not differ across conditions. The present findings support, even if only partially, the idea that enactment promotes learning of abstract words and that it is superior to enrichment by means of pictures even after short training.

Adaptation of Stability during Perturbed Walking in Parkinson's Disease

Gait and balance disorders are major problems that contribute to falls among subjects with Parkinson's disease (PD). Strengthening the compensatory responses through the use of balance perturbations may improve balance in PD. To date, it is unclear how PD affects the ability to react and adapt to perturbations delivered while walking. This study aims to investigate how PD affects the ability to walk, respond to balance perturbations, and produce acute short-term effects to improve compensatory reactions and gait stability. A cable-driven robot was used to train nine patients with PD and nine age-matched controls with multidirectional waist-pull perturbations while walking on a treadmill. Margin of stability and base of support were evaluated while walking without cables and reacting to the perturbations. PD was associated with a reduced stability in the forward direction and the inability to produce proactive anticipatory adjustments. Both groups were able to improve the response to the disturbances and produce short-term aftereffects of increased gait stability once the cables were removed. A single session of perturbation-based balance training produced acute effects that ameliorated gait instability in PD. This result is encouraging for designing new therapeutic interventions that remediate falls risk.

Procedural Motor Learning in Children With Specific Language Impairment

PURPOSE

Specific language impairment (SLI) is a developmental disorder that affects language and motor development in the absence of a clear cause. An explanation for these impairments is offered by the procedural deficit hypothesis (PDH), which argues that motor difficulties in SLI are due to deficits in procedural memory. The aim of this study was to test the PDH by examining the procedural motor learning abilities of children with and without SLI.

METHOD

Thirteen children with SLI and 14 age-matched typically developing children completed the following procedural measures: (a) a knot-tying task as a measure of motor sequencing and (2) a mirror-drawing task as a measure of visual-motor adaptation.

RESULTS

Although children with SLI produced significantly more errors on certain knot-tying tasks, they performed comparably on others. Also, children with SLI performed comparably with typically developing children on the mirror-drawing task.

CONCLUSIONS

The PDH requires reframing. The sequence learning deficits in SLI are modest and specific to more difficult tasks. Visual-motor adaptation, on the other hand, appears to be unaffected in SLI.

Handwriting Analysis in Parkinson's Disease: Current Status and Future Directions

BACKGROUND

The majority of patients with Parkinson's disease (PD) have handwriting abnormalities. Micrographia (abnormally small letter size) is the most commonly reported and easily detectable handwriting abnormality in patients with PD. However, micrographia is perhaps the tip of the iceberg representing the handwriting abnormalities in PD. Digitizing tablet technology, which has evolved over the last 2 decades, has made it possible to study the pressure and kinematic features of handwriting. This has resulted in a surge of studies investigating graphomotor impairment in patients with PD.

METHODS

The objectives of this study were to review the evolution of the kinematic analysis of handwriting in PD and to provide an overview of handwriting abnormalities observed in PD along with future directions for research in this field. Articles for review were searched from the PubMed and SCOPUS databases.

RESULTS

Digitizing tablet technologies have resulted in a shift of focus from the analysis of only letter size to the analysis of several kinematic features of handwriting. Studies based on the kinematic analysis of handwriting have revealed that patients with PD may have abnormalities in velocity, fluency, and acceleration in addition to micrographia. The recognition of abnormalities in several kinematic parameters of handwriting has given rise to the term PD dysgraphia. In addition, certain kinematic properties potentially may be helpful in distinguishing PD from other parkinsonian disorders.

CONCLUSION

The journey from micrographia to PD dysgraphia is indeed a paradigm shift. Further research is warranted to gain better insight into the graphomotor impairments in PD and their clinical implications.

The Neuropsychology of Movement and Movement Disorders: Neuroanatomical and Cognitive Considerations

This paper highlights major developments over the past two to three decades in the neuropsychology of movement and its disorders. We focus on studies in healthy individuals and patients, which have identified cognitive contributions to movement control and animal work that has delineated the neural circuitry that makes these interactions possible. We cover advances in three major areas: (1) the neuroanatomical aspects of the "motor" system with an emphasis on multiple parallel circuits that include cortical, corticostriate, and corticocerebellar connections; (2) behavioral paradigms that have enabled an appreciation of the cognitive influences on the preparation and execution of movement; and (3) hemispheric differences (exemplified by limb praxis, motor sequencing, and motor learning). Finally, we discuss the clinical implications of this work, and make suggestions for future research in this area. (JINS, 2017, 23, 768-777).