Acute exercise performed before and after motor practice enhances the positive effects on motor memory consolidation

Performing a single bout of exercise can enhance motor learning and long-term retention of motor skills. Parameters such as the intensity and when the exercise bout is performed in relation to skill practice (i.e., timing) likely influence the effectiveness. However, it is still not fully understood how exercise should be administered to maximize its effects and how exercise interacts with distinct components of skill learning. Here, we expand this knowledge by investigating the potential synergistic effects of performing acute exercise both prior to and following motor practice. Sixty-four, able-bodied, young adult male participants practiced a sequential visuomotor accuracy tracking (SVAT) task requiring rapid and accurate force modulation and high levels of precision control using intrinsic hand muscles. The task also contained a repeated pattern of targets that allowed sequence-specific skill improvements. Sequential and non-sequential motor performance was assessed at baseline, immediately after motor practice, and again seven days later. One group performed moderate-intensity exercise before practice (PREMO), a second group performed high-intensity exercise after practice (POSTHI), a third group exercised both before and after practice (PREMO + POSTHI), and a fourth group did not exercise during these periods (CON). Regardless of the exercise condition, acute exercise improved long-term retention of the skill by countering performance decay between experimental sessions (i.e., a 7-day interval). Furthermore, exercising both before and after motor practice led to the greatest improvements in skilled performance over time. We found that the effects of exercise were not specific to the practiced sequence. Namely, the effects of exercise generalized across sequential and non-sequential target positions and orders. This suggests that acute exercise works through mechanisms that promote general aspects of motor memory (e.g., lasting improvements in fast and accurate motor execution). The results demonstrate that various exercise protocols can promote the stabilization and long-term retention of motor skills. This effect can be enhanced when exercise is performed both before and after practice.

Effects of acute cardiovascular exercise on motor memory encoding and consolidation: A systematic review with meta-analysis

Emerging evidence indicates that acute bouts of cardiovascular exercise promote motor memory formation. In this preregistered meta-analysis (CRD42018106288) we synthesize data from 22 studies published until February 2020, including a total of 862 participants. We calculated standardized mean differences (SMDs) with 95 % confidence intervals (CIs) to assess exercise effects on motor memory encoding and consolidation, respectively. The pooled data indicate that exercise mainly benefits the consolidation of memories, with exercise prior to motor practice improving early non-sleep consolidation (SMD, 0.58; 95 % CI, 0.30-0.86; p < 0.001), and post-practice exercise facilitating sleep-dependent consolidation (SMD, 0.62; 95 % CI, 0.34-0.90; p < 0.001). Strongest effects exist for high exercise intensities, and motor task nature appears to be another relevant modulator. We demonstrate that acute cardiovascular exercise particularly promotes the consolidation of acquired motor memories, and exercise timing, and intensity as well as motor task nature seem to critically modulate this relationship. These findings are discussed within currently proposed models of motor memory formation and considering molecular and systemic mechanisms of neural plasticity.

Beyond action observation: Neurobehavioral mechanisms of memory for visually perceived bodies and actions

Examining the processing of others' body-related information in the perceivers' brain (action observation) is a key topic in cognitive neuroscience. However, what happens beyond the perceptual stage, when the body is not within view and it is transformed into an associative form that can be stored, updated, and later recalled, remains poorly understood. Here we examine neurobehavioural evidence on the memory processing of visually perceived bodily stimuli (dynamic actions and images of bodies). The reviewed studies indicate that encoding and maintaining bodily stimuli in memory recruits the sensorimotor system. This process arises when bodily stimuli are either recalled through action recognition or reproduction. Interestingly, the memory capacity for these stimuli is rather limited: only 2 or 3 bodily stimuli can be simultaneously held in memory. Moreover, this process is disrupted by increasing concurrent bodily operations; i.e., moving one's body, seeing or memorising additional bodies. Overall, the evidence suggests that the neural circuitry allowing us to move and feel ourselves supports the encoding, retention, and memory recall of others' visually perceived bodies.

Quantitative Proteomics Reveals Distinct Molecular Signatures of Different Cerebellum-Dependent Learning Paradigms

The cerebellum improves motor performance by adjusting motor gain appropriately. As de novo protein synthesis is essential for the formation and retention of memories, we hypothesized that motor learning in the opposite direction would induce a distinct pattern of protein expression in the cerebellum. We conducted quantitative proteomic profiling to compare the level of protein expression in the cerebellum at 1 and 24 h after training from mice that underwent different paradigms of cerebellum-dependent oculomotor learning from specific directional changes in motor gain. We quantified a total of 43 proteins that were significantly regulated in each of the three learning paradigms in the cerebellum at 1 and 24 h after learning. In addition, functional enrichment analysis identified protein groups that were differentially enriched or depleted in the cerebellum at 24 h after the three oculomotor learnings, suggesting that distinct biological pathways may be engaged in the formation of three oculomotor memories. Weighted correlation network analysis discovered groups of proteins significantly correlated with oculomotor memory. Finally, four proteins (Snca, Sncb, Cttn, and Stmn1) from the protein group correlated with the learning amount after oculomotor training were validated by Western blot. This study provides a comprehensive and unbiased list of proteins related to three cerebellum-dependent motor learning paradigms, suggesting the distinct nature of protein expression in the cerebellum for each learning paradigm. The proteomics data have been deposited to the ProteomeXchange Consortium with identifiers <PXD008433>.

Time-dependent motor memory representations in prefrontal cortex

How memories evolve over time is fundamental for understanding memory. Hippocampus-dependent episodic memories are generally assumed to undergo a time-dependent neural reorganization involving an increased reliance on neocortical areas. Yet, whether other forms of memory undergo a similar reorganization over time remains unclear. Here, we examined whether the neural underpinnings of motor sequence memories change over time. Participants were trained on a motor sequence learning task. Either 1d or 28d later, they performed a retention test for this task in the fMRI scanner. Sequence-specific motor memory was observed both 1d and 28d after initial training. Bayesian second-level fMRI analyses suggested a higher probability for task activity in the middle frontal gyrus and frontal pole 28d compared to 1d after initial motor learning. Searchlight representational similarity analysis indicated that areas in middle and superior frontal cortex were more involved in differentiating between multivariate activity patterns for old motor sequence memories and newly learned motor sequences in the 28d-group compared to the 1d-group. This increased involvement of lateral frontal areas during the task after 28 days was not paralleled by a decrease in those areas that were involved in performing the motor sequence retention task after 1d. These novel findings provide insights into how memories beyond the hippocampus evolve over time.

The use of motor imagery training to retain the performance improvement following physical practice in the elderly

With physiological aging, appears a deterioration of the ability to retain motor skills newly acquired. In this study, we tested the beneficial role of motor imagery training to compensate this deterioration. We tested four groups: young control group (n = 10), elderly control group (n = 10), young mental-training group (n = 13) and elderly mental-training group (n = 13). In pre- and post-tests, the participants performed three trials on a dexterity manual task (the Nine Hole Peg Test), commonly used in clinic. We recorded the movement duration as a factor of performance. Each trial, including 36 arm movements, consisted in manipulating sticks as fast as possible. The control groups watched a non-emotional documentary for 30 min and the mental-training groups imagined the task (50 trials). First, we observed a speed improvement during the pre-test session for all groups. Immediately after viewing the movie (post-test 1), the young control group showed a preservation of motor performance in comparison to the performance measured before the break (pret-test 3), while the young mental-training group improved performance after motor imagery practice. For the elderly, the control group showed a deterioration of motor performance at post-test 1, attesting a deterioration of the ability to retain motor skills with aging. Interestingly, the elderly mental-training group showed a preservation of motor performance between the pre-test 3 and the post-test 1. The present findings demonstrate the beneficial role of mental training with motor imagery to retain the performance improvement following physical practice in the elderly. This method could be an alternative to prevent the deterioration of motor skills.

Spontaneous recovery of conditioned eyeblink responses is associated with transiently decreased cerebellar theta activity in guinea pigs

Behavioral studies have demonstrated that extinguished conditioned eyeblink responses (CR) can spontaneously recover after extinction. However, the neural mechanisms underlying this process are still unclear. We have shown that spontaneous cerebellar theta activity was predictive of subsequent CR extinction. Here, we sought to further evaluate the association between spontaneous recovery and cerebellar theta activity in behaving guinea pigs. It was found that trace conditioning training significantly diminished the degree of spontaneous recovery during extinction sessions as compared to delay training. Moreover, by recording local field potential in the cerebellum of guinea pigs undergoing an eyeblink conditioning extinction task, we found that spontaneous recovery of delay-paradigm CRs was associated with transiently decreased CS-evoked theta activity in the cerebellum. These findings suggest that decreased CS-evoked cerebellar theta activity may contribute to the neural process that is important for the spontaneous recovery of extinguished motor memory. Future studies are needed to clarify the neural mechanism underlying changed cerebellar theta activity during altered behavioral contingencies.

Reconsolidation of human motor memory: From boundary conditions to behavioral interventions-How far are we from clinical applications?

The memory reconsolidation hypothesis states that a previously consolidated and stable memory can return to a temporary labile state after retrieved, requiring a new stabilization process. During the labile period, the memory trace is vulnerable to modification, which provides a potential therapeutic opportunity to weaken, updated or strengthen that memory. As such, reconsolidation has been the subject of numerous studies in different domains of human memory that seek strategies to treat post-traumatic disorders and erase or modify pathological memories. A few studies have also investigated the impairment effects of behavioral interferences on motor memory. However, very little has been researched and written about the possibility of using reconsolidation to enhance motor skill learning. Here, we present a critical review of the literature and trace possible applications for human motor memory reconsolidation. We discuss the boundary conditions and the mechanisms to trigger the reconsolidation process, as well as the effects of behavioral interventions in modifying the performance of motor skills.

Independent voluntary correction and savings in locomotor learning

Humans can acquire new walking patterns in many different ways. For example, we can change our gait voluntarily in response to instruction or adapt by sensing our movement errors. Here, we investigated how acquisition of a new walking pattern through simultaneous voluntary correction and adaptive learning affected the resulting motor memory of the learned pattern. We studied adaptation to split-belt treadmill walking with and without visual feedback of stepping patterns. As expected, visual feedback enabled faster acquisition of the new walking pattern. However, upon later re-exposure to the same split-belt perturbation, participants exhibited similar motor memories whether they had learned with or without visual feedback. Participants who received feedback did not re-engage the mechanism used to accelerate initial acquisition of the new walking pattern to similarly accelerate subsequent relearning. These findings reveal that voluntary correction neither benefits nor interferes with the ability to save a new walking pattern over time.

Children benefit differently from night- and day-time sleep in motor learning

Motor skill acquisition occurs while practicing (on-line) and when asleep or awake (off-line). However, developmental questions still remain about whether children of various ages benefit similarly or differentially from night- and day-time sleeping. The likely circadian effects (time-of-day) and the possible between-test-interference (order effects) associated with children's off-line motor learning are currently unknown. Therefore, this study examines the contributions of over-night sleeping and mid-day napping to procedural skill learning. One hundred and eight children were instructed to practice a finger sequence task using computer keyboards. After an equivalent 11-h interval in one of the three states (sleep, nap, wakefulness), children performed the same sequence in retention tests and a novel sequence in transfer tests. Changes in the movement time and sequence accuracy were evaluated between ages (6-7, 8-9, 10-11years) during practice, and from skill training to retrievals across three states. Results suggest that night-time sleeping and day-time napping improved the tapping speed, especially for the 6-year-olds. The circadian factor did not affect off-line motor learning in children. The interference between the two counter-balanced retrieval tests was not found for the off-line motor learning. This research offers possible evidence about the age-related motor learning characteristics in children and a potential means for enhancing developmental motor skills. The dynamics between age, experience, memory formation, and the theoretical implications of motor skill acquisition are discussed.

Retention of the "first-trial effect" in gait-slip among community-living older adults

"First-trial effect" characterizes the rapid adaptive behavior that changes the performance outcome (from fall to non-fall) after merely a single exposure to postural disturbance. The purpose of this study was to investigate how long the first-trial effect could last. Seventy-five (≥ 65 years) community-dwelling older adults, who were protected by an overhead full body harness system, were retested for a single slip 6-12 months after their initial exposure to a single gait-slip. Subjects' body kinematics that was used to compute their proactive (feedforward) and reactive (feedback) control of stability was recorded by an eight-camera motion analysis system. We found the laboratory falls of subjects on their retest slip were significantly lower than that on the novel initial slip, and the reactive stability of these subjects was also significantly improved. However, the proactive stability of subjects remains unchanged between their initial slip and retest slip. The fall rates and stability control had no difference among the 6-, 9-, and 12-month retest groups, which indicated a maximum retention on 12 months after a single slip in the laboratory. These results highlighted the importance of the "first-trial effect" and suggested that perturbation training is effective for fall prevention, with lower trial doses for a long period (up to 1 year). Therefore, single slip training might benefit those older adults who could not tolerate larger doses in reality.

Sleep-dependent motor memory consolidation in older adults depends on task demands

It is often suggested that sleep-dependent consolidation of motor learning is impaired in older adults. The current study challenges this view and suggests that the degree of motor consolidation seen with sleep in older age groups depends on the kinematic demands of the task. We show that, when tested with a classic sequence learning task, requiring individuated finger movements, older adults did not show sleep-dependent consolidation. By contrast, when tested with an adapted sequence learning task, in which movements were performed with the whole hand, sleep-dependent motor improvement was observed in older adults. We suggest that age-related decline in fine motor dexterity may in part be responsible for the previously described deficit in sleep-dependent motor consolidation with aging.

Aging increases the susceptibility to motor memory interference and reduces off-line gains in motor skill learning

Declines in the ability to learn motor skills in older adults are commonly attributed to deficits in the encoding of sensorimotor information during motor practice. We investigated whether aging also impairs motor memory consolidation by assessing the susceptibility to memory interference and off-line gains in motor skill learning after practice in children, young, and older adults. Subjects performed a ballistic task (A) followed by an accuracy-tracking task (B) designed to disrupt the consolidation of A. Retention tests of A were performed immediately and 24 hours after B. Older adults showed greater susceptibility to memory interference and no off-line gains in motor skill learning. Performing B produced memory interference and reduced off-line gains only in the older group. However, older adults also showed deficits in memory consolidation independent of the interfering effects of B. Age-related declines in motor skill learning are not produced exclusively by deficits in the encoding of sensorimotor information during practice. Aging also increases the susceptibility to memory interference and reduces off-line gains in motor skill learning after practice.