Consolidation Of Motor Learning Research Articles

Sleep and motor learning in stroke (SMiLES): a longitudinal study investigating sleep-dependent consolidation of motor sequence learning in the context of recovery after stroke

IntroductionThere is growing evidence that sleep is disrupted after stroke, with worse sleep relating to poorer motor outcomes. It is also widely acknowledged that consolidation of motor learning, a critical...

Reward timing matters in motor learning

SummaryReward timing, that is, the delay after which reward is delivered following an action is known to strongly influence reinforcement learning. Here, we asked if reward timing could also modulate how people learn and consolidate new motor skills. In 60 healthy participants, we found that delaying reward delivery by a few seconds influenced motor learning. Indeed, training with a short reward delay (1 s) induced continuous improvements in performance, whereas a long reward delay (6 s) led to initially high learning rates that were followed by an early plateau in the learning curve and a lower performance at the end of training. Participants who learned the skill with a long reward delay also exhibited reduced overnight memory consolidation. Overall, our data show that reward timing affects the dynamics and consolidation of motor learning, a finding that could be exploited in future rehabilitation programs.

Retention of touchscreen skills is compromised in Parkinson’s disease

Fine motor skill impairments likely have a severe impact on the use of touchscreens in Parkinson’s disease (PD). Although recent work showed positive effects of intensive writing training, many questions remained regarding the consolidation of motor learning in PD. The current study examined the effects of PD on practicing the manipulation of touchscreen technology and whether this can lead to 24h-retention and transfer. We developed the Swipe-Slide Pattern (SSP)-task, similar to handling a touchscreen unlock-trace. On day 1, 11 patients and 10 healthy, age-matched controls underwent two consecutive runs of early and late learning (9 × 36 s SSP and 36 s rest). This was followed by a retention test after 24 h, including the assessment of transfer. Movement time (MT, s), Euclidean distance (ED) and a performance index (PI = MT/ED) were compared across the learning phases (early, late, retention and transfer) for both groups. Additionally, a learning, retention and transfer index were compared between groups and correlated to clinical characteristics. Both groups significantly improved in MT and PI across practice. However, while healthy adults showed further improvements after a 24h-retention period, patients presented with impaired retention indices. This was correlated with disease duration, disease severity and performance on a daily life mobile phone task. Finally, transfer to a similar, but untrained pattern was comparable between both groups. Overall, short-term practice of the SSP-task results in improvements for PD patients, albeit with impaired retention. Future work should investigate whether prolonged touchscreen skill training can be retained in motor memory in PD.

Visuomotor learning and unlearning in children and adolescents with tourette syndrome

Tourette syndrome (TS) is a childhood-onset neurological condition characterised by an evolving repertoire of chronic motor tics and one or more phonic tics. Tics, like habits, are inflexible and repetitive behaviours that are acquired over a period of time. It has been proposed that tics arise in TS as a result of increased habit learning: which may bias the child to acquire automatic behaviours (i.e., tics) more readily than is normal and make it harder to unlearn maladaptive habits once they have been acquired. Using a well-established visuomotor adaptation task, we investigated motor learning in a group of children and adolescents with a clinical diagnosis of TS relative to a group of age and gender matched typically developing individuals. In particular, we quantified differences in the strength and quality of motor learning and unlearning in TS, and the consolidation of motor learning over a 24 h washout period. We demonstrated that there was a marginally significant decrease in learning rate in the individuals with TS relative to age and gender matched typically developing controls. However, this effect was not associated with tic severity and could be entirely accounted for by the severity of co-occurring ADHD symptoms. Thus, once ADHD symptoms had been accounted for, there were no between group differences in learning rate or the degree of learning observed. By contrast, and more importantly, we found that following learning the rate of forgetting (unlearning) was significantly negatively associated with motor tic severity, such that individuals with more severe tics took longer to unlearn previously learnt motor patterns of behaviour. This finding is consistent with the proposal that TS is associated with alterations in the striatal habit learning system and with the view that TS may make it harder to unlearn maladaptive motor habits once they have been acquired.

T006 How might brain stimulation enhance consolidation of motor learning?

Performance increments following a training intervention are secured and sometimes generated by a process termed consolidation. As healthy older humans express lesser consolidation that young people this group might constitute a population particularly well suited to study consolidation. We will review the evidence whether and how brain stimulation enhances consolidation by modulating physiological mechanisms following the training. To demonstrate that brain stimulation is capable to modulate consolidation requires that its effects on performance indices be disambiguated from effects on performance. Transcranial direct current stimulation (tDCS) applied after motor training improved consolidation of explicit motor sequence learning in older controls. Anodal, but not cathodal, tDCS to M1, but not to PMd, led to performance improvements at retesting 8 h after initial learning. Only application of tDCS immediately after the end of training, but not after 1 or 2 h, enhanced offline consolidation. These results will be discussed against evidence provided by others (Tunovic et al., J Neurosci, 2014) that off-line stimulation may rescue consolidation through counteracting activity-dependent decreases of M1 excitability. These findings may suggest a model that brain stimulation may enhance consolidation by preventing post-training inhibitory action in M1 that may originate in premotor cortex.

Theta EEG neurofeedback benefits early consolidation of motor sequence learning.

Procedural learning is subject to consolidation processes believed to depend on the modulation of functional connections involved in representing the acquired skill. While sleep provides the most commonly studied framework for such consolidation processes, posttraining modulation of oscillatory brain activity may also impact on plasticity processes. Under the hypothesis that consolidation of motor learning is associated with theta band activity, we used EEG neurofeedback (NFB) to enable participants to selectively increase either theta or beta power in their EEG spectra following the acquisition phase of motor sequence learning. We tested performance on a motor task before and after training, right after the NFB session to assess immediate NFB effects, 1 day after NFB to assess interaction between NFB effects and overnight sleep-dependent stabilization, and 1 week after the initial session, to assess the effects of NFB on long-term stabilization of motor training. We also explored the extent of the influence of single-electrode NFB on EEG recorded across the scalp. Results revealed a significantly greater improvement in performance immediately after NFB in the theta group than in the beta group. This effect continued for testing up to 1 week following training. Across participants, post-NFB improvement correlated positively with theta/beta ratio change achieved during NFB. Additionally, NFB was found to cause widespread band-power modulation beyond the electrode used for feedback. Thus, upregulating postlearning theta power may yield contributions to the immediate performance and subsequent consolidation of an acquired motor skill.

Relearning of Writing Skills in Parkinson's Disease After Intensive Amplitude Training.

Micrographia occurs in approximately 60% of people with Parkinson's disease (PD). Although handwriting is an important task in daily life, it is not clear whether relearning and consolidation (ie the solid storage in motor memory) of this skill is possible in PD. The objective was to conduct for the first time a controlled study into the effects of intensive motor learning to improve micrographia in PD. In this placebo-controlled study, 38 right-handed people with PD were randomized into 2 groups, receiving 1 of 2 equally time-intensive training programs (30 min/day, 5 days/week for 6 weeks). The experimental group (n = 18) performed amplitude training focused at improving writing size. The placebo group (n = 20) received stretch and relaxation exercises. Participants' writing skills were assessed using a touch-sensitive writing tablet and a pen-and-paper test, pre- and posttraining, and after a 6-week retention period. The primary outcome was change in amplitude during several tests of consolidation: (1) transfer, using trained and untrained sequences performed with and without target zones; and (2) automatization, using single- and dual-task sequences. The group receiving amplitude training significantly improved in amplitude and variability of amplitude on the transfer and automatization task. Effect sizes varied between 7% and 17%, and these benefits were maintained after the 6-week retention period. Moreover, there was transfer to daily life writing. These results show automatization, transfer, and retention of increased writing size (diminished micrographia) after intensive amplitude training, indicating that consolidation of motor learning is possible in PD. © 2016 International Parkinson and Movement Disorder Society.

Dopamine systems adaptation during acquisition and consolidation of a skill.

The striatum plays a key role in motor learning. Striatal function depends strongly on dopaminergic neurotransmission, but little is known about neuroadaptions of the dopamine system during striatal learning. Using an established task that allows differentiation between acquisition and consolidation of motor learning, we here investigate D1 and D2-like receptor binding and transcriptional levels after initial and long-term training of mice. We found profound reduction in D1 binding within the dorsomedial striatum (DMS) after the first training session on the accelerated rotarod and a progressive reduction in D2-like binding within the dorsolateral striatum (DLS) after extended training. Given that similar phase- and region-specific striatal neuroadaptations have been found also during learning of complex procedural tasks including habit formation and automatic responding, the here observed neurochemical alterations are important for our understanding of neuropsychiatric disorders that show a dysbalance in the function of striatal circuits, such as in addictive behaviors.

S14-4. Possibility of a useful intervention of exercise induced by muscle fatigue to change excitabilities of corticospinal and cortico-cortical tracts for functional recovery in neurorehabilitation

Motor learning and synaptic plasticity in the cortex are enhanced by interventions that reduce the effectiveness of GABAergic intracortical inhibition. The disinhibition of SICI by muscle fatigue could enhance synaptic plasticity and improve the consolidation of motor learning. We found that the corticospinal excitability and SICI decrease after exhaustive muscle contraction or muscle fatigue. It seems possible that decreased SICI can enhance synaptic plasticity if motor learning or skill training is combined with muscle fatigue. Interestingly, fatigue in muscles on the opposite side of the body or in lower limb muscles reduces the corticospinal excitability and disinhibit SICI in non-exercised arm or upper limb muscles during the recovery period. It is possible that muscle fatigue of the unaffected hands can act indirectly and positively on the motor function of affected hands in patients with chronic stroke and that we imagine incorporating such a technique in treatment of stroke, by inducing muscle fatigue in non-paretic lower limbs prior to neurorehabilitation of paretic upper limbs. Muscle fatigue can influence corticospinal and cortico-cortical excitability in various areas of motor cortex directly or indirectly and may be able to improve task performance in a bimanual motor skill.

Visual deprivation induces long-term memory consolidation of saccadic adaptation

Consolidation of motor learning is a complex process exceeding the duration of the practice. Saccadic adaptation as the response to a altering visual environment is a form of motor learning, wherein two temporal components seem to be involved in its consolidation: A long term learning process that leads to a slow but enduring effect, and a short term learning process that leads to a fast but less enduring effect1. It has also been shown that an adapted amplitude can be maintained even days after one adaptation session2. Up to now, extinction of saccadic adaptation was thought to be based on time and visual input.

Acquisition of context-specific adaptation is enhanced with rest intervals between changes in context state, suggesting a new form of motor consolidation

We previously showed that the saccadic system could be adapted in a context-specific manner: two different adapted gains could be associated with two different context cues, with the gain state switched when the context state was switched. This was accomplished by alternating context/adaptation states several times over the course of an adaptation session, and assessing saccade gain in each context state before and after adaptation. One context cue we studied was vertical eye position; an adaptive gain increase was induced with the eyes up 10°, and an adaptive gain decrease with the eyes down 10°. This context cue was only partially effective: there was considerable undesired transfer of adaptation from the eyes-down condition (gain-decrease) to the eyes-up condition (gain-increase), with the result that there was little or no gain-increase adaptation. One explanation for this is that the two context/adaptation states, presented one after the other, interfered with each other. In the present study, we tested this hypothesis by interposing one-minute rest intervals between each alternation in context/adaptation state. The resulting context-specific adaptation is greatly improved (relative to the case when there are no rest intervals): both gain-increase and gain-decrease adaptations are stronger and occur more rapidly. This effect resembles that found in studies on the consolidation of motor learning, although such consolidation is believed to occur over much longer time spans (hours rather than minutes).