Facilitate Motor Learning Research Articles

Effects of virtual body-representation on motor skill learning

Motor learning is often hindered or facilitated by visual information from one’s body and its movement. However, it is unclear whether visual representation of the body itself facilitates motor learning. Thus, we tested the effects of virtual body-representation on motor learning through a virtual reality rotary pursuit task. In the task, visual feedback on participants’ movements was identical, but virtual body-representation differed by dividing the experimental conditions into three conditions: non-avatar, non-hand avatar, and hand-shaped avatar. We measured the differences in the rate of motor learning, body-ownership, and sense of agency in the three conditions. Although there were no differences in body-ownership and sense of agency between the conditions, the hand-shaped avatar condition was significantly superior to the other conditions in the rate of learning. These findings suggest that visually recognizing one’s body shape facilitates motor learning.

Easy Task and Choice: Motivational Interventions Facilitate Motor Skill Learning in Children

Expectancies for success and autonomy support have been shown to facilitate motor learning and enhance motor performance. The purpose of the study was to examine whether we replicated (a) enhanced expectancies and autonomy support intervention enhanced motor skill learning in children, and (b) identified the underlying psychological mechanism. Sixty children kicked soccer balls with their dominant leg to a squared area target. Participants were randomly assigned to one of the four groups: enhanced expectancies and autonomy support (EE/AS), enhanced expectancies (EE), autonomy support (AS), or control (CON) groups. Participants learning the skill were or were not provided enhanced expectation instructions by making the task success easier and provided an opportunity to choose one of the three colored balls during their practice. Two days later, they performed retention and transfer tests. Results indicated that the EE/AS group had the highest scores, with main effects of autonomy support being significant and enhanced expectancies being marginally significant for the retention test and significant for the transfer test. The EE/AS group had the highest self-efficacy and perceived choice scores. Therefore, having high expectancies for success and being autonomous were important ingredients for facilitating motor skill learning in children.

Utilising an internal focus of attention during preparation and an external focus during execution may facilitate motor learning

ABSTRACT Research with athletes and coaches has found that attentional focus strategies are more complex than using an internal or external focus exclusively. Recently Becker et al. [2020, March 1. The effects of attentional focus in the preparation and execution of a standing long jump. Psychological Research, 84(2), 285–291] found that switching attentional focus from internal in movement preparation to external during movement execution provided a benefit over internal focus and control conditions. The purpose of this study was to investigate the effects of attentional switching on motor skill acquisition. 79 participants were randomly divided into an internal (INT), external (EXT), or switching group (IES). Individuals performed 80 acquisition trials of a golf chipping task with their prescribed attentional focus during preparation and execution. 24-hours later 10-trial retention and transfer tests were performed. The primary analysis revealed significant improvement during acquisition (p < .001) but no significant differences between attentional focus groups during acquisition, retention, or transfer. A secondary analysis was performed with individuals low in attentional focus adherence removed (<60%). Groups significantly improved during acquisition (p < .001). For retention IES significantly outperformed INT (p < .05). These results suggest that the detrimental effects of an internal focus are only found during skill execution and not movement preparation. It is possible for learners to benefit from both an internal and external focus so long as the cues are provided during the correct phase of skill performance. Highlights Attentional focus is much more complex than using either an internal or external focus of attention. This study investigated the effects of switching attention during skill acquisition from an internal to external focus. A preliminary analysis revealed no significant differences between attentional focus groups of internal, external, or switching. One reason for this finding was the poor adherence to the prescribed focus cue. A secondary analysis where low adherence individuals were removed revealed a significant difference between the switching group and the internal focus group during retention. These finding suggest that the detrimental effects associated with an internal focus of attention are exclusive to using the focus during task execution. It is possible that an internal focus can still facilitate learning so long as an external focus is used during movement execution.

Meta-analyzing enhanced expectancies on motor learning: positive effects but methodological concerns

ABSTRACT The OPTIMAL theory of motor learning predicts enhanced expectancies facilitate learning. This meta-analysis investigated this prediction by quantifying effect sizes from studies manipulating feedback after good trials, comparative feedback, perceived task difficulty, conceptions of ability, self-modeling, or extrinsic rewards, and assessing learning. After searching databases, 48 studies met inclusion criteria for quantitative analysis. Fifty-six effect sizes were calculated from performance differences between enhanced expectancies and neutral/diminished expectancies groups at delayed retention tests. Results revealed a Hedges’ g = 0.54 (95% CI [0.38, 0.69]) that may be overestimated due to small-study effects and underpowered studies. Moderator analyses revealed feedback after good trials, comparative feedback, perceived task difficulty, and conceptions of ability manipulations significantly improved learning. Few studies used other manipulations, precluding reliable estimates of their effects. Further, significant effects of enhanced expectancies were shown for children/adolescents, young adults, and older adults. Few studies examined special populations, preventing a reliable effect estimate. Finally, the effect of enhanced expectancies on learning was not affected by type of comparison group (neutral/diminished expectancies). Findings suggest enhanced expectancies may facilitate motor learning, consistent with OPTIMAL theory, but pre-registered/registered reports and more powerful studies should be conducted to confirm the effect and estimate its size more accurately.

High Gamma and Beta Temporal Interference Stimulation in the Human Motor Cortex Improves Motor Functions.

Background: Temporal interference (TI) stimulation is a new technique of non-invasive brain stimulation. Envelope-modulated waveforms with two high-frequency carriers can activate neurons in target brain regions without stimulating the overlying cortex, which has been validated in mouse brains. However, whether TI stimulation can work on the human brain has not been elucidated.Objective: To assess the effectiveness of the envelope-modulated waveform of TI stimulation on the human primary motor cortex (M1).Methods: Participants attended three sessions of 30-min TI stimulation during a random reaction time task (RRTT) or a serial reaction time task (SRTT). Motor cortex excitability was measured before and after TI stimulation.Results: In the RRTT experiment, only 70 Hz TI stimulation had a promoting effect on the reaction time (RT) performance and excitability of the motor cortex compared to sham stimulation. Meanwhile, compared with the sham condition, only 20 Hz TI stimulation significantly facilitated motor learning in the SRTT experiment, which was significantly positively correlated with the increase in motor evoked potential.Conclusion: These results indicate that the envelope-modulated waveform of TI stimulation has a significant promoting effect on human motor functions, experimentally suggesting the effectiveness of TI stimulation in humans for the first time and paving the way for further explorations.

Long-Term Myoelectric Training with Delayed Feedback in the Home Environment.

Myoelectric prosthesis users typically do not receive immediate feedback from their device. They must be able to consistently produce distinct muscle activations in the absence of augmented feedback. In previous experiments, abstract decoding has provided real-time visual feedback for closed loop control. It is unclear if the performance in those experiments was due to short-term adaptation or motor learning. To test if similar performance could be reached without short-term adaptation, we trained participants with a delayed feedback paradigm. Feedback was delayed until after the ~1.5 s trial was completed. Three participants trained for five days in their home environments, completing a cumulative total of 4920 trials. Participants became highly accurate while receiving no real-time feedback of their control input. They were also able to retain performance gains across days. This strongly suggests that abstract decoding with delayed feedback facilitates motor learning, enabling four class control without immediate feedback.

Effects of and Response to Mechanical Loading on the Knee.

Mechanical loading to the knee joint results in a differential response based on the local capacity of the tissues (ligament, tendon, meniscus, cartilage, and bone) and how those tissues subsequently adapt to that load at the molecular and cellular level. Participation in cutting, pivoting, and jumping sports predisposes the knee to the risk of injury. In this narrative review, we describe different mechanisms of loading that can result in excessive loads to the knee, leading to ligamentous, musculotendinous, meniscal, and chondral injuries or maladaptations. Following injury (or surgery) to structures around the knee, the primary goal of rehabilitation is to maximize the patient's response to exercise at the current level of function, while minimizing the risk of re-injury to the healing tissue. Clinicians should have a clear understanding of the specific injured tissue(s), and rehabilitation should be driven by knowledge of tissue-healing constraints, knee complex and lower extremity biomechanics, neuromuscular physiology, task-specific activities involving weight-bearing and non-weight-bearing conditions, and training principles. We provide a practical application for prescribing loading progressions of exercises, functional activities, and mobility tasks based on their mechanical load profile to knee-specific structures during the rehabilitation process. Various loading interventions can be used by clinicians to produce physical stress to address body function, physical impairments, activity limitations, and participation restrictions. By modifying the mechanical load elements, clinicians can alter the tissue adaptations, facilitate motor learning, and resolve corresponding physical impairments. Providing different loads that create variable tensile, compressive, and shear deformation on the tissue through mechanotransduction and specificity can promote the appropriate stress adaptations to increase tissue capacity and injury tolerance. Tools for monitoring rehabilitation training loads to the knee are proposed to assess the reactivity of the knee joint to mechanical loading to monitor excessive mechanical loads and facilitate optimal rehabilitation.

Physical therapy treatments incorporating equine movement: a pilot study exploring interactions between children with cerebral palsy and the horse

BackgroundPhysical therapy treatments incorporating equine movement are recognized as an effective tool to treat functional mobility and balance in children with cerebral palsy (CP). To date, only a few studies examined kinematic outputs of the horses and children when mounted. In this pilot study, to better understand the effectiveness of this type of treatment, we examined the interaction between the horses and children with CP during physical therapy sessions where equine movement was utilized.MethodsFour children with CP participated in eight physical therapy sessions incorporating hippotherapy as a treatment intervention. Functional mobility was assessed using the Timed Up Go or the 10 m Walk Test. Inertial measurement unit sensors, attached to children and horses, recorded movements and tracked acceleration, angular velocity, and body orientation. Correlation between vertical accelerations of children and horses were analyzed. In addition, peak frequencies of vertical accelerations of children and horses were compared.ResultsFunctional tests modestly improved over time. The children’s movements, (quantified in frequency and temporal domains) increasingly synchronized to the vertical movement of the horse’s walk, demonstrated by reduced frequency errors and increased correlation.ConclusionsThe findings suggest that as the sessions progressed, the participants appeared to become more familiar with the horse’s movement. Since the horse’s gait at a walk mimics the human gait this type of treatment may provide individuals with CP, who have abnormal gait patterns, an opportunity for their neuromuscular system to experience a typical gait pattern. The horse’s movement at the walk are consistent, cyclical, rhythmical, reciprocal and multi-dimensional, all of which can facilitate motor learning. The increased synchronization between horse and the mounted participant suggests that physical therapy utilizing equine movement is a viable treatment tool to enhance functional mobility. This study may provide a useful baseline for future work.Trial registrationTexas A&M University Institutional Review Board. IRB2018-0064. Registered 8 March 2018. Link: https://rcb.tamu.edu/humans/irb and https://github.com/pilwonhur/HPOT

Enhanced error facilitates motor learning in weight shift and increases use of the paretic leg during walking at chronic stage after stroke.

The purpose of this study was to determine whether the application of lateral pelvis pulling force toward the non-paretic side during the stance phase of the paretic leg would enhance forced use of the paretic leg and increase weight shift toward the paretic side in stroke survivors. Eleven chronic stroke survivors participated in two experimental sessions, which consisted of (1) treadmill walking with the application of "pelvis resistance" or "pelvis assistance" and (2) overground walking. During the treadmill walking, the laterally pulling force was applied during the stance phase of the paretic leg toward the non-paretic side for the "pelvis resistance" condition or toward the paretic side for the "pelvis assistance" condition during the stance phase of the paretic leg. After force release, the "pelvis resistance" condition exhibited greater enhancement in muscle activation of hip ABD, ADD, and SOL and greater improvement in lateral weight shift toward the paretic side, compared with the effect of the "pelvis assistance" condition (P < 0.03). This improved lateral weight shift was associated with the enhanced muscle activation of hip ABD and ADD (R2 = 0.67, P = 0.01). The pelvis resistance condition also improved overground walking speed and stance phase symmetry when measured 10min after the treadmill walking (P = 0.004). In conclusion, applying pelvis resistance forces to increase error signals may facilitate motor learning of weight shift toward the paretic side and enhance use of the paretic leg in chronic stroke survivors. Results from this study may be utilized to develop an intervention approach to improve walking in stroke survivors.

Motor Learning Based on Oscillatory Brain Activity Using Transcranial Alternating Current Stimulation: A Review.

Developing effective tools and strategies to promote motor learning is a high-priority scientific and clinical goal. In particular, motor-related areas have been investigated as potential targets to facilitate motor learning by noninvasive brain stimulation (NIBS). In addition to shedding light on the relationship between motor function and oscillatory brain activity, transcranial alternating current stimulation (tACS), which can noninvasively entrain oscillatory brain activity and modulate oscillatory brain communication, has attracted attention as a possible technique to promote motor learning. This review focuses on the use of tACS to enhance motor learning through the manipulation of oscillatory brain activity and its potential clinical applications. We discuss a potential tACS–based approach to ameliorate motor deficits by correcting abnormal oscillatory brain activity and promoting appropriate oscillatory communication in patients after stroke or with Parkinson’s disease. Interpersonal tACS approaches to manipulate intra- and inter-brain communication may result in pro-social effects and could promote the teaching–learning process during rehabilitation sessions with a therapist. The approach of re-establishing oscillatory brain communication through tACS could be effective for motor recovery and might eventually drive the design of new neurorehabilitation approaches based on motor learning.

Increased motor variability facilitates motor learning in weight shift toward the paretic side during walking in individuals post-stroke.

The purpose of this study was to determine whether applying "varied" versus constant pelvis assistance force mediolaterally toward the paretic side of stroke survivors during walking would result in short-term improvement in weight shift toward the paretic side. Twelve individuals post-stroke (60.4±6.2years; gait speed: 0.53±0.19m/s) were tested under two conditions (varied vs. constant). Each condition was conducted in a single separate session, which consisted of (a) treadmill walking with no assistance force for 1min (baseline), pelvis assistance toward the paretic side for 9min (adaptation), and then no force for additional 1min (post-adaptation), and (b) overground walking. In the "varied" condition, the magnitude of force was randomly changed across steps between 30% and 100% of the predetermined amount. In the abrupt condition, the magnitude of force was kept constant at 100% of the predetermined amount. Participants exhibited greater improvements in weight shift toward the paretic side (p<0.01) and in muscle activity of plantar flexors and hip adductors of the paretic leg (p=0.02) from baseline to late post-adaptation period for the varied condition than for the constant condition. Motor variability of the peak pelvis displacement at baseline was correlated with improvement in weight shift toward the paretic side after training for the varied (R2 =0.64, p=0.01) and the constant condition (R2 =0.39, p=0.03). These findings suggest that increased motor variability, induced by applying the varied pelvis assistance, may facilitate motor learning in weight shift and gait symmetry during walking in individuals post-stroke.

Implicit and Explicit Motor Learning Interventions Have Similar Effects on Walking Speed in People After Stroke: A Randomized Controlled Trial.

ObjectiveClinicians may use implicit or explicit motor learning approaches to facilitate motor learning of patients with stroke. Implicit motor learning approaches have shown promising results in healthy populations. The purpose of this study was to assess whether an implicit motor learning walking intervention is more effective compared with an explicit motor learning walking intervention delivered at home regarding walking speed in people after stroke in the chronic phase of recovery.MethodsThis randomized, controlled, single-blind trial was conducted in the home environment. The 79 participants, who were in the chronic phase after stroke (age = 66.4 [SD = 11.0] years; time poststroke = 70.1 [SD = 64.3] months; walking speed = 0.7 [SD = 0.3] m/s; Berg Balance Scale score = 44.5 [SD = 9.5]), were randomly assigned to an implicit (n = 38) or explicit (n = 41) group. Analogy learning was used as the implicit motor learning walking intervention, whereas the explicit motor learning walking intervention consisted of detailed verbal instructions. Both groups received 9 training sessions (30 minutes each), for a period of 3 weeks, targeted at improving quality of walking. The primary outcome was walking speed measured by the 10-Meter Walk Test at a comfortable walking pace. Outcomes were assessed at baseline, immediately after intervention, and 1 month postintervention.ResultsNo statistically or clinically relevant differences between groups were obtained postintervention (between-group difference was estimated at 0.02 m/s [95% CI = −0.04 to 0.08] and at follow-up (between-group difference estimated at −0.02 m/s [95% CI = −0.09 to 0.05]).ConclusionImplicit motor learning was not superior to explicit motor learning to improve walking speed in people after stroke in the chronic phase of recovery.ImpactTo our knowledge, this is the first study to examine the effects of implicit compared with explicit motor learning on a functional task in people after stroke. Results indicate that physical therapists can use (tailored) implicit and explicit motor learning strategies to improve walking speed in people after stroke who are in the chronic phase of recovery.

Effects of an external focus of attention and target occlusion on performance in virtual reality.

The use of virtual reality as a training mechanism continues to gain popularity as equipment becomes more readily available. It is important to not only understand the relationship between virtual reality training and motor learning, but to understand the extent to which practice manipulations enhance performance in virtual reality. One common practice manipulation is adopting an external focus of attention, which has been shown to facilitate motor learning in a variety tasks. The purposes of the present study were to investigate the effectiveness of an external focus of attention and the effects of target occlusion times in virtual reality. Fifty-six participants performed a single-leg long jump during baseline, training, and retention and were randomly assigned to either an external or control group. During baseline and retention, all participants performed the task in both a virtual reality (VR) and real world (RW) environments. Training was all done in VR where participants were provided an external focus cue or no cue. Results revealed that individuals jumped significantly further in RW than VR in both baseline and retention (p<.001). During training, the external group jumped significantly further than control (p<.05). These results suggest that the adoption of an external focus improves performance during training. However, we did not see a benefit of an external focus in retention. These findings should be taken into consideration when using virtual reality as a training tool when performance must be transferred to a real world environment.

Functional Use of Eye Movements for an Acting System.

Movements of the eyes assist vision and support hand and body movements in a cooperative way. Despite their strong functional coupling, different types of movements are usually studied independently. We integrate knowledge from behavioral, neurophysiological, and clinical studies on how eye movements are coordinated with goal-directed hand movements and how they facilitate motor learning. Understanding the coordinated control of eye and hand movements can provide important insights into brain functions that are essential for performing or learning daily tasks in health and disease. This knowledge can also inform applications such as robotic manipulation and clinical rehabilitation.

Effects of Transcranial Direct Current Stimulation on Motor Function in Children 8-12 Years With Developmental Coordination Disorder: A Randomized Controlled Trial.

Background and objectives: Developmental coordination disorder (DCD) is a neurodevelopmental motor disorder occurring in 5-6% of school-aged children. It is suggested that children with DCD show deficits in motor learning. Transcranial direct current stimulation (tDCS) enhances motor learning in adults and children but is unstudied in DCD. We aimed to investigate if tDCS, paired with motor skill training, facilitates motor learning in a pediatric sample with DCD.Methods: Twenty-eight children with diagnosed DCD (22 males, mean age: 10.62 ± 1.44 years) were randomized and placed into a treatment or sham group. Anodal tDCS was applied (1 mA, 20 min) in conjunction with fine manual training over 5 consecutive days. Children's motor functioning was assessed with the Purdue Pegboard Test and Jebsen-Taylor Hand Function Test at baseline, post-intervention and 6 weeks following intervention. Group differences in rates of motor learning and skill transfer/retention were examined using linear mixed modeling and repeated measures ANOVAs, respectively.Results: There were no serious adverse events or drop-outs and procedures were well-tolerated. Independent of group, all participants demonstrated improved motor scores over the 5 training days [F(69.280), p < 0.001, 95% CI (0.152, 0.376)], with no skill decay observed at retention. There was no interaction between intervention group and day [F(2.998), p = 0.086, 95% CI (−0.020, 0.297)].Conclusion: Children with DCD demonstrate motor learning with long-term retention of acquired skill. Motor cortex tDCS did not enhance motor learning as seen in other populations. Before conclusions of tDCS efficacy can be drawn, additional carefully designed trials with reproducible results are required.Clinical Trial Registration: ClinicalTrials.gov: NCT03453983

Determining the Intracortical Responses After a Single Session of Aerobic Exercise in Young Healthy Individuals: A Systematic Review and Best Evidence Synthesis.

Alibazi, RJ, Pearce, AJ, Rostami, M, Frazer, AK, Brownstein, C, and Kidgell, DJ. Determining the intracortical responses after a single session of aerobic exercise in young healthy individuals: a systematic review and best evidence synthesis. J Strength Cond Res 35(2): 562-575, 2021-A single bout of aerobic exercise (AE) may induce changes in the excitability of the intracortical circuits of the primary motor cortex (M1). Similar to noninvasive brain stimulation techniques, such as transcranial direct current stimulation, AE could be used as a priming technique to facilitate motor learning. This review examined the effect of AE on modulating intracortical excitability and inhibition in human subjects. A systematic review, according to PRISMA guidelines, identified studies by database searching, hand searching, and citation tracking between inception and the last week of February 2020. Methodological quality of included studies was determined using the Downs and Black quality index and Cochrane Collaboration of risk of bias tool. Data were synthesized and analyzed using best-evidence synthesis. There was strong evidence for AE not to change corticospinal excitability and conflicting evidence for increasing intracortical facilitation and reducing silent period and long-interval cortical inhibition. Aerobic exercise did reduce short-interval cortical inhibition, which suggests AE modulates the excitability of the short-latency inhibitory circuits within the M1; however, given the small number of included studies, it remains unclear how AE affects all circuits. In light of the above, AE may have important implications during periods of rehabilitation, whereby priming AE could be used to facilitate motor learning.

Audio Feedback for Device-Supported Balance Training: Parameter Mapping and Influencing Factors

Recent studies suggest that real-time auditory feedback is an effective method to facilitate motor learning. The evaluation of the parameter mapping (sound-to-movement mapping) is a crucial, yet frequently neglected step in the development of audio feedback. We therefore conducted two experiments to evaluate audio parameters with target finding exercises designed for balance training. In the first experiment with ten participants, five different audio parameters were evaluated on the X-axis (mediolateral movement). Following that, in a larger experiment with twenty participants in a two-dimensional plane (mediolateral and anterior-posterior movement), a basic and synthetic audio model was compared to a more complex audio model with musical characteristics. Participants were able to orient themselves and find the targets with the audio models. In the one-dimensional condition of experiment one, percussion sounds and synthetic sound wavering were the overall most effective audio parameters. In experiment two, the synthetic model was more effective and better evaluated by the participants. In general, basic sounds were more helpful than complex (musical) sound models. Musical abilities and age were correlated with certain exercise scores. Audio feedback is a promising approach for balance training and should be evaluated with patients. Preliminary evaluation of the respective parameter mapping is highly advisable.

Expert Event Segmentation of Dance Is Genre-Specific and Primes Verbal Memory.

By chunking continuous streams of action into ordered, discrete, and meaningful units, event segmentation facilitates motor learning. While expertise in the observed repertoire reduces the frequency of event borders, generalization of this effect to unfamiliar genres of dance and among other sensorimotor experts (musicians, athletes) remains unknown, and was the first aim of this study. Due to significant overlap in visuomotor, language, and memory processing brain networks, the second aim of this study was to investigate whether visually priming expert motor schemas improves memory for words related to one’s expertise. A total of 112 participants in six groups (ballet, Bharatanatyam, and “other” dancers, athletes, musicians, and non-experts) segmented a ballet dance, a Bharatanatyam dance, and a non-dance control sequence. To test verbal memory, participants performed a retrieval-induced forgetting task between segmentation blocks. Dance, instrument, and sport word categories were included to probe the second study aim. Results of the event segmentation paradigm clarify that previously-established expert segmentation effects are specific to familiar genres of dance, and do not transfer between different types of experts or to non-dance sequences. Greater recall of dance category words among ballet and Bharatanatyam dancers provides novel evidence for improved verbal memory primed by activating familiar sensorimotor representations.

A Single Bout of High-intensity Interval Exercise Increases Corticospinal Excitability, Brain-derived Neurotrophic Factor, and Uncarboxylated Osteolcalcin in Sedentary, Healthy Males

Exercise induces neuroplasticity in descending motor pathways facilitating motor learning, and as such it could be utilized as an intervention in neurorehabilitation, for example when re-learning motor skills after stroke. To date, however, the neurophysiological and molecular mechanisms underlying exercise-induced neuroplasticity remain largely unknown impeding the potential utilization of exercise protocols as ‘motor learning boosters’ in clinical and non-clinical settings. Here, we assessed corticospinal excitability, intracortical facilitation (ICF) and short-interval intracortical inhibition (SICI) using transcranial magnetic stimulation (TMS) and serum biochemical markers including brain-derived neurotrophic factor (BDNF), total and precursor cathepsin B (tCTSB, proCTSB), uncarboxylated and carboxylated osteocalcin (unOCN, cOCN) and irisin using ELISA. Measurements were carried out in sedentary, healthy males before and after a single session of high-intensity interval exercise (HIIE) or in individuals who rested and did not perform exercise (No Exercise). We found that HIIE increased corticospinal excitability, BDNF and unOCN, and decreased cOCN. We also determined that greater increases in BDNF were associated with increases in unOCN and irisin and decreases in cOCN only in participants who underwent HIIE, suggesting that unOCN and irisin may contribute to exercise-induced BDNF increases. Conversely, no changes other than a decrease in serum unOCN/tOCN were found in No Exercise participants. The present findings show that a single session of HIIE is sufficient to modulate corticospinal excitability and to increase BDNF and unOCN in sedentary, healthy males.

Exploring disturbance as a force for good in motor learning.

Disturbance forces facilitate motor learning, but theoretical explanations for this counterintuitive phenomenon are lacking. Smooth arm movements require predictions (inference) about the force-field associated with a workspace. The Free Energy Principle (FEP) suggests that such ‘active inference’ is driven by ‘surprise’. We used these insights to create a formal model that explains why disturbance might help learning. In two experiments, participants undertook a continuous tracking task where they learned how to move their arm in different directions through a novel 3D force field. We compared baseline performance before and after exposure to the novel field to quantify learning. In Experiment 1, the exposure phases (but not the baseline measures) were delivered under three different conditions: (i) robot haptic assistance; (ii) no guidance; (iii) robot haptic disturbance. The disturbance group showed the best learning as our model predicted. Experiment 2 further tested our FEP inspired model. Assistive and/or disturbance forces were applied as a function of performance (low surprise), and compared to a random error manipulation (high surprise). The random group showed the most improvement as predicted by the model. Thus, motor learning can be conceptualised as a process of entropy reduction. Short term motor strategies (e.g. global impedance) can mitigate unexpected perturbations, but continuous movements require active inference about external force-fields in order to create accurate internal models of the external world (motor learning). Our findings reconcile research on the relationship between noise, variability, and motor learning, and show that information is the currency of motor learning.