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Muscle memory is a form of procedural memory that involves consolidating a specific motor task into memory through repetition, which has been used synonymously with motor learning. When a movement is repeated over time, the brain creates a long-term muscle memory for that task, eventually allowing it to be performed with little to no conscious effort. This process decreases the need for attention and creates maximum efficiency within the motor and memory systems. Muscle memory is found in many everyday activities that become automatic and improve with practice, such as riding , driving , playing ball sports, musical instruments, and poker, Poker Face: How to win poker at the table and online - Judi James. typing on keyboards, entering PINs, performing martial arts, swimming, dancing, and drawing.
In the early stages of empirical research of motor memory Edward Thorndike, a leading pioneer in the study of motor memory, was among the first to acknowledge learning can occur without conscious awareness. One of the earliest and most notable studies regarding the retention of motor skills was by Hill, Rejall, and Thorndike, who showed savings in relearning typing skills after a 25-year period with no practice. Findings related to the retention of learned motor skills have been continuously replicated in studies, suggesting that through subsequent practice, motor learning is stored in the brain as memory. This is why performing skills such as riding a bike or driving a car are effortlessly and 'subconsciously' executed, even if someone had not performed these skills in a long period of time.
The memory encoding stage is often referred to as motor learning, and requires an increase in brain activity in motor areas as well as an increase in attention. Brain areas active during motor learning include the motor and somatosensory cortices; however, these areas of activation decrease once the motor skill is learned. The prefrontal and frontal cortices are also active during this stage due to the need for increased attention on the task being learned.
The main area involved in motor learning is the cerebellum. Some models of cerebellar-dependent motor learning, in particular the Marr-Albus model, propose a single plasticity mechanism involving the cerebellar long-term depression (LTD) of the parallel fiber synapses onto Purkinje cells. These modifications in synapse activity would mediate motor input with motor outputs critical to inducing motor learning. However, conflicting evidence suggests that a single plasticity mechanism is not sufficient and a multiple plasticity mechanism are needed to account for the storage of motor memories over time. Regardless of the mechanism, studies of cerebellar-dependent motor tasks show that cerebral cortical plasticity is crucial for motor learning, even if not necessarily for storage.
The basal ganglia also play an important role in memory and learning, in particular in reference to stimulus-response associations and the formation of habits. The basal ganglia-cerebellar connections are thought to increase with time when learning a motor task.
While the exact location of muscle memory storage is not known, studies have suggested that it is the inter-regional connections that play the most important role in advancing motor memory encoding to consolidation, rather than decreases in overall regional activity. These studies have shown a weakened connection from the cerebellum to the primary motor area with practice, it is presumed, because of a decreased need for error correction from the cerebellum. However, the connection between the basal ganglia and the primary motor area is strengthened, suggesting the basal ganglia play an important role in the motor memory consolidation process.
Sleep duration and exercise also influence motor skill learning and memory. It has been proven through experiments that sleep after night training improves skill consolidation compared to morning training without sleep . This therefore implies that sleep is a time of heightened processing and consolidation of motor learning, allowing athletes and individuals maximizing their motor skills to attain maximum performance.
Furthermore, formal sleep therapies have also been discovered to enhance the performance of sports through enhanced reaction time, coordination, and overall execution of skills. Maintenance of proper quantities of sleep in addition to strict compliance to consistency in sleeping schedule can maximize the results of motor learning as well as support long-term memory for body skills . The application of sleep-based interventions, including following a constant sleeping pattern and minimizing disruptions to an absolute degree, can therefore be a significant assistant for the person who wants to optimize their motor capacity.
Evidence has shown that increases in strength occur well before muscle hypertrophy, and decreases in strength due to detraining or ceasing to repeat the exercise over an extended period of time precede muscle atrophy. To be specific, strength training enhances motor neuron excitability and induces synaptogenesis, both of which would help in enhancing communication between the nervous system and the muscles themselves. , neuromuscular efficacy is not altered within a two-week time period following cessation of the muscle usage; instead, it is merely the neuron's ability to excite the muscle that declines in correlation with the muscle's decrease in strength. This confirms that muscle strength is first influenced by the inner neural circuitry, rather than by external physiological changes in the muscle size.
Previously untrained muscles will acquire newly formed nuclei through the fusion of satellite cells preceding hypertrophy. Subsequent detraining will result in atrophy and the loss of myo-nuclei. While it was long believed that a muscle memory effect related to myo-nuclei permanence existed, current studies establish that during detraining, myo-nuclei will be lost.
Reorganization of motor maps within the cortex are not altered in either strength or endurance training. However, within the motor cortex, endurance induces angiogenesis within as little as three weeks to increase blood flow to the involved regions. In addition, neurotropic factors within the motor cortex are upregulated in response to endurance training to promote neural survival.
Skilled motor tasks have been divided into two distinct phases: a fast-learning phase, in which an optimal plan for performance is established, and a slow-learning phase, in which longer-term structural modifications are made on specific motor modules. Even a small amount of training may be enough to induce neural processes that continue to evolve even after the training has stopped, which provides a potential basis for consolidation of the task. In addition, studying mice while they are learning a new complex reaching task, has found that "motor learning leads to rapid formation of dendritic spines (spinogenesis) in the motor cortex contralateral to the reaching forelimb". However, motor cortex reorganization itself does not occur at a uniform rate across training periods. It has been suggested that the synaptogenesis and motor map reorganization merely represent the consolidation, and not the acquisition itself, of a specific motor task. Furthermore, the degree of plasticity in various locations (namely motor cortex versus spinal cord) is dependent on the behavioural demands and nature of the task (i.e., skilled reaching versus strength training).
Whether strength or endurance related, it is plausible that the majority of motor movements would require a skilled moving task of some form, whether it be maintaining proper form when paddling a canoe, sitting with a neutral posture, or bench pressing a heavier weight. Endurance training assists the formation of these new neural representations within the motor cortex by up regulating neurotropic factors that could enhance the survival of the newer neural maps formed due to the skilled movement training. Strength training results are seen in the spinal cord well before any physiological muscular adaptation is established through muscle hypertrophy or atrophy. The results of endurance and strength training, and skilled reaching, therefore, combine to help each other maximize performance output.
More recently, research has suggested that epigenetics may play a distinct role in orchestrating a muscle memory phenomenon Indeed, previously untrained human participants experienced a chronic period of resistance exercise training (7 weeks) that evoked significant increases in skeletal muscle mass of the vastus lateralis muscle, in the quadriceps muscle group. Following a similar period of physical in-activity (7 weeks), where strength and muscle mass returned to baseline, participants performed a secondary period of resistance exercise. Importantly, these participants adapted in an enhanced manner, whereby the amount of skeletal muscle mass gained was greater in the second period of muscle growth than the first, suggesting a muscle memory concept. The researchers went on to examine the human epigenome in order to understand how DNA methylation may aid in creating this effect. During the first period of resistance exercise, the authors identify significant adaptations in the human methylome, whereby over 9,000 CpG sites were reported as being significantly hypomethylated, with these adaptations being sustained during the subsequent period of physical in-activity. However, upon secondary exposure to resistance exercise, a greater frequency of hypomethylated CpG sites was observed, where over 18,000 sites reported as being significantly hypomethylated. The authors went on to identify how these changes altered the expression of relevant transcripts, and subsequently correlated these changes with adaptations in skeletal muscle mass. Collectively, the authors conclude that skeletal muscle mass and muscle memory phenomenon is, at least in part, modulated due to changes in DNA methylation. Further work is now needed to confirm and explore these findings.
Certain human behaviours, especially actions like the finger movements in musical performances, are very complex and require many interconnected neural networks where information can be transmitted across multiple brain regions. It has been found that there are often functional differences in the brains of professional musicians, when compared to other individuals. This is thought to reflect the musician's innate ability, which may be fostered by an early exposure to musical training. An example of this is bimanual synchronized finger movements, which play an essential role in piano playing. It is suggested that bimanual coordination can come only from years of bimanual training, where such actions become adaptations of the motor areas. When comparing professional musicians to a control group in complex bimanual movements, professionals are found to use an extensive motor network much less than those non-professionals. This is because professionals rely on a motor system that has increased efficiency, and, therefore, those less trained have a network that is more strongly activated. It is implied that the untrained pianists have to invest more neuronal activity to have the same level of performance that is achieved by professionals. This, yet again, is said to be a consequence of many years of motor training and experience that helps form a fine motor memory skill of musical performance.
It is often reported that, when a pianist hears a well-trained piece of music, synonymous fingering can be involuntarily triggered. This implies that there is a coupling between the perception of music and the motor activity of those musically trained individuals. Therefore, one's muscle memory in the context of music can easily be triggered when one hears certain familiar pieces. Overall, long-term musical fine motor training allows for complex actions to be performed at a lower level of movement control, monitoring, selection, attention, and timing. This leaves room for musicians to focus attention synchronously elsewhere, such as on the artistic aspect of the performance, without having to consciously control one's fine motor actions.
As Edward S. Casey notes in Remembering, Second Edition: A Phenomenological Study, declarative memory, a process that involves an initial fragile learning period. "The activity of the past, in short, resides in its habitual enactment in the present."
This patient was diagnosed with a pure form of dysgraphia of letters, meaning he had no other speech or reading impairments. His impairment was specific to letters in the alphabet. He was able to copy letters from the alphabet, but he was not able to write these letters. He had previously been rated average on the Wechsler Adult Intelligence Scale's vocabulary subtest for writing ability comparative to his age before his diagnosis. His writing impairment consisted of difficulty remembering motor movements associated with the letters he was supposed to write. He was able to copy the letters, and also form images that were similar to the letters. This suggests that dysgraphia for letters is a deficit related to motor memory. Somehow there is a distinct process within the brain related to writing letters, which is dissociated from copying and drawing letter-like items.
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