Muscle memory
Encyclopedia
Muscle memory has been used synonymously with motor learning
Motor learning
Motor learning is a “relatively permanent” change, resulting from practice or a novel experience, in the capability for responding...

, which is a form of procedural memory
Procedural memory
Procedural memory is memory for how to do things. Procedural memory guides the processes we perform and most frequently resides below the level of conscious awareness. When needed, procedural memories are automatically retrieved and utilized for the execution of the integrated procedures involved...

 that involves consolidating a specific motor task into memory through repetition. When a movement is repeated over time, a long-term muscle memory is created for that task, eventually allowing it to be performed without conscious effort. This process decreases the need for attention and creates maximum efficiency within the motor and memory systems. Examples of muscle memory are found in many everyday activities that become automatic and improve with practice, such as riding a bicycle, typing on a keyboard, playing a melody or phrase on a musical instrument, playing video games, or performing different algorithms for a puzzle cube
Rubik's Cube
Rubik's Cube is a 3-D mechanical puzzle invented in 1974 by Hungarian sculptor and professor of architecture Ernő Rubik.Originally called the "Magic Cube", the puzzle was licensed by Rubik to be sold by Ideal Toy Corp. in 1980 and won the German Game of the Year special award for Best Puzzle that...

.

Movement and motor learning

Movement is a critical part of our life, and it is a major component of our evolutionary development; without it, we could not survive. It has been suggested that our developed cognitive capacities evolved so we could make movements essential to our survival. For example, cognitive abilities evolved so we could use tools, build shelter, and hunt for animals.

The origins of research for the acquisition of motor skills stem from philosophers such as Plato
Plato
Plato , was a Classical Greek philosopher, mathematician, student of Socrates, writer of philosophical dialogues, and founder of the Academy in Athens, the first institution of higher learning in the Western world. Along with his mentor, Socrates, and his student, Aristotle, Plato helped to lay the...

, Aristotle
Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...

 and Galen
Galen
Aelius Galenus or Claudius Galenus , better known as Galen of Pergamon , was a prominent Roman physician, surgeon and philosopher...

. Friedrich Bessel
Friedrich Bessel
-References:* John Frederick William Herschel, A brief notice of the life, researches, and discoveries of Friedrich Wilhelm Bessel, London: Barclay, 1847 -External links:...

 is a philosopher who is especially noteworthy, as he was among the first to empirically observe motor learning
Motor learning
Motor learning is a “relatively permanent” change, resulting from practice or a novel experience, in the capability for responding...

. Bessel tried to observe the difference in his colleagues with the method in which they recorded the transit time of stars.

Retention

The retention of motor skills, now referred to as muscle memory, also began to be of great interest in the early 1900s. Most motor skills are thought to be acquired through practice; however, mere observation of the skill has led to learning as well. Research suggests we do not start off with a blank slate with regard to motor memory although we do learn most of our motor memory repertoire during our lifetime. Movements such as facial expressions, which are thought to be learned, can actually be observed in children who are blind; thus there is some evidence for motor memory being genetically pre-wired.

In the early stages of empirical research of motor memory Edward Thorndike
Edward Thorndike
Edward Lee "Ted" Thorndike was an American psychologist who spent nearly his entire career at Teachers College, Columbia University. His work on animal behavior and the learning process led to the theory of connectionism and helped lay the scientific foundation for modern educational psychology...

, 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 ‘unconsciously’ executed, even if someone had not performed these skills in a long period of time.

Motor behavior

When first learning a motor task, movement is often slow, stiff and easily disrupted without attention. With practice, execution of motor task becomes smoother, there is a decrease in limb stiffness, and muscle activity necessary to the task is performed without conscious effort.

Muscle memory encoding

The neuroanatomy of memory
Neuroanatomy of memory
The neuroanatomy of memory encompasses a wide variety of anatomical structures in the brain.- Hippocampus :The hippocampus is a structure in the brain that has been associated with various memory functions. It is part of the limbic system, and lies next to the medial temporal lobe...

 is widespread throughout the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...

; however, the pathways important to motor memory are separate from the medial temporal lobe
Temporal lobe
The temporal lobe is a region of the cerebral cortex that is located beneath the Sylvian fissure on both cerebral hemispheres of the mammalian brain....

 pathways associated with declarative memory
Declarative memory
Declarative memory is one of two types of long term human memory. It refers to memories which can be consciously recalled such as facts and knowledge. Its counterpart is known as non-declarative or Procedural memory, which refers to unconscious memories such as skills...

. As with declarative memory, motor memory is theorized to have two stages: a short-term memory encoding stage, which is fragile and susceptible to damage, and a long-term memory consolidation
Memory consolidation
Memory consolidation is a category of processes that stabilize a memory trace after the initial acquisition. Consolidation is distinguished into two specific processes, synaptic consolidation, which occurs within the first few hours after learning, and system consolidation, where...

 stage, which is more stable.

The memory encoding stage is often referred to as motor learning
Motor learning
Motor learning is a “relatively permanent” change, resulting from practice or a novel experience, in the capability for responding...

, 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
Cerebellum
The cerebellum is a region of the brain that plays an important role in motor control. It may also be involved in some cognitive functions such as attention and language, and in regulating fear and pleasure responses, but its movement-related functions are the most solidly established...

. 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 modification 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 is 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
Basal ganglia
The basal ganglia are a group of nuclei of varied origin in the brains of vertebrates that act as a cohesive functional unit. They are situated at the base of the forebrain and are strongly connected with the cerebral cortex, thalamus and other brain areas...

 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.

Muscle memory consolidation

Muscle memory consolidation involves the continuous evolution of neural processes after practicing a task has stopped. The exact mechanism of motor memory consolidation within the brain is controversial; however, most theories assume that there is a general redistribution of information across the brain from encoding to consolidation. Hebb's rule states that “synaptic connectivity changes as a function of repetitive firing.” In this case, that would mean that the high amount of stimulation coming from practicing a movement would cause the repetition of firing in certain motor networks; presumably leading to an increase in the efficiency of exciting these motor networks over time.

Though 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 plays an important role in the motor memory consolidation process.

Strength training and adaptations

When participating in any sport, new motor skills and movement combinations are frequently being used and repeated. All sports require some degree of strength, endurance training, and skilled reaching in order to be successful in the required tasks. Muscle memory related to strength training
Muscle memory (strength training)
Muscle memory has been used to describe the observation that various muscle-related tasks seem to be easier to perform after previous practice, even if the task has not been performed for a while. It is as if the muscles “remember”. The term could relate to tasks as disparate as playing the...

 probably involves elements of both motor learning, described below, and long-lasting changes in the muscle tissue.

Evidence has shown that increases in strength occur well before muscle hypertrophy
Hypertrophy
Hypertrophy is the increase in the volume of an organ or tissue due to the enlargement of its component cells. It should be distinguished from hyperplasia, in which the cells remain approximately the same size but increase in number...

, and decreases in strength due to detraining or ceasing to repeat the exercise over an extended period of time precede muscle atrophy
Atrophy
Atrophy is the partial or complete wasting away of a part of the body. Causes of atrophy include mutations , poor nourishment, poor circulation, loss of hormonal support, loss of nerve supply to the target organ, disuse or lack of exercise or disease intrinsic to the tissue itself...

. To be specific, strength training enhances motor neuron
Motor neuron
In vertebrates, the term motor neuron classically applies to neurons located in the central nervous system that project their axons outside the CNS and directly or indirectly control muscles...

 excitability and induces synaptogenesis
Synaptogenesis
Synaptogenesis is the formation of synapses. Although it occurs throughout a healthy person's lifespan, an explosion of synapse formation occurs during early brain development...

, both of which would help in enhancing communication between the nervous system and the muscles themselves. However, neuromuscular efficacy is not altered within a two-week time period following cessation of the muscle usage; instead, it is merely the neuron
Neuron
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...

'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.

Reorganization of motor maps within the cortex are not altered in either strength or endurance training. However, within the motor cortex, endurance induces angiogenesis
Angiogenesis
Angiogenesis is the physiological process involving the growth of new blood vessels from pre-existing vessels. Though there has been some debate over terminology, vasculogenesis is the term used for spontaneous blood-vessel formation, and intussusception is the term for the formation of new blood...

 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
Motor cortex
Motor cortex is a term that describes regions of the cerebral cortex involved in the planning, control, and execution of voluntary motor functions.-Anatomy of the motor cortex :The motor cortex can be divided into four main parts:...

 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, 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.

Fine motor memory

Fine motor skills are often discussed in terms of transitive movements, which are those done when using tools (which could be as simple as a tooth brush or pencil). Transitive movements have representations that become programmed to the premotor cortex
Premotor cortex
The premotor cortex is an area of motor cortex lying within the frontal lobe of the brain. It extends 3 mm anterior to the primary motor cortex, near the Sylvian fissure, before narrowing to approximately 1 mm near the medial longitudinal fissure, which serves as the posterior border for...

, creating motor programs that result in the activation of the motor cortex
Motor cortex
Motor cortex is a term that describes regions of the cerebral cortex involved in the planning, control, and execution of voluntary motor functions.-Anatomy of the motor cortex :The motor cortex can be divided into four main parts:...

 and therefore the motor movements. In a study testing the motor memory of patterned finger movements (a fine motor skill) it was found that retention of certain skills are susceptible to disruption if another task interferes with one’s motor memory. However, such susceptibility can be reduced with time. For example, if a finger pattern is learned, then another is learned six hours later the original pattern will still be remembered, while learning such patterns back to back may cause forgetting of the initial one. Furthermore, the heavy use of computers by recent generations has both positive and negative effects. It was found that one of the main positive effects is that it enhances fine motor skills of children. Repetitive behaviours, such as typing on a computer from a young age, can enhance such abilities. Therefore, by beginning computer use at an early age, muscle memory may be activated earlier.

Music memory

Fine motor skills are very important in playing musical instruments. It was found that muscle memory is relied on when playing the clarinet, specifically to help create special effects through certain tongue movements when blowing air into the instrument. Memorizing is done by muscles as a note is seen and recalled, its auditory pair is learned and is matched by fingers movements (a fine motor skill). When reproducing a motor action, you must have previous experience with it to memorize set actions. If there is no previous experience there will be no mental image of the motion, and therefore no actual movement.

Certain human behaviours, especially actions like the fingering 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.

Puzzle Cube memory

Speed cubers often will use muscle memory in order to learn large amounts of algorithms
Algorithm
In mathematics and computer science, an algorithm is an effective method expressed as a finite list of well-defined instructions for calculating a function. Algorithms are used for calculation, data processing, and automated reasoning...

 quickly. It is quickly found that memorization purely of letters corresponding to moves on the cube is extremely difficult. The average beginner will try to do something like this, however an advanced cuber can learn much more efficiently with muscle memory. A simple repetition of algorithms will create a long-term knowledge of it. This plays a role in major speedcubing methods such as Fridrich for the 3x3x3 Rubik's cube
Rubik's Cube
Rubik's Cube is a 3-D mechanical puzzle invented in 1974 by Hungarian sculptor and professor of architecture Ernő Rubik.Originally called the "Magic Cube", the puzzle was licensed by Rubik to be sold by Ideal Toy Corp. in 1980 and won the German Game of the Year special award for Best Puzzle that...

 and EG for the 2x2x2 Pocket cube
Pocket Cube
The Pocket Cube is the 2×2×2 equivalent of a Rubik's Cube. The cube consists of 8 pieces, all corners.-Permutations:...

.

Gross motor memory

Gross motor skill
Gross motor skill
Gross motor skills are the abilities usually acquired during infancy and early childhood as part of a child's motor development. By the time they reach two years of age, almost all children are able to stand up, walk and run, walk up stairs, etc...

s are concerned with the movement of large muscles, or major body movements, such as those involved in walking or kicking, and are associated with normal development. The extent to which one exhibits gross motor skills depends largely on their muscle tone and the strength. In a study looking at people with Down Syndrome, it was found that the pre-existing deficits, with regard to verbal-motor performance, has an impact on limiting the individuals transfer of gross motor skills following visual and verbal instruction to verbal instruction only. The fact that the individuals could still exhibit two of the three original motor skills may have been a result of positive transfer in which previous exposure allows the individual to remember the motion, under the visual and verbal trial, and then later perform it under the verbal trial.

Learning in childhood

The way in which a child learns a gross motor skill can impact how long it takes to consolidate it and be able to reproduce the movement. In a study with preschoolers, looking at the role of self-instruction on acquiring complex gross motor chains using ballet
Ballet
Ballet is a type of performance dance, that originated in the Italian Renaissance courts of the 15th century, and which was further developed in France and Russia as a concert dance form. The early portions preceded the invention of the proscenium stage and were presented in large chambers with...

 positions, it was found that the motor skills were better learned and remembered with the self-instruction procedure over the no-self-instruction procedure. This suggests that the use of self-instruction will increase the speed with which a preschooler will learn and remember a gross motor skill. It was also found that, once the preschoolers learned and mastered the motor chain movements, they ceased the use of self-instruction. This suggests that the memory for the movements became strong enough that there was no longer a need for self-instruction and the movements could be reproduced without it.

Impact of Alzheimer's disease

It has been suggested that consistent practice of a gross motor skill can help a patient with Alzheimer’s Disease learn and remember that skill. It was thought that the damage to the hippocampus
Hippocampus
The hippocampus is a major component of the brains of humans and other vertebrates. It belongs to the limbic system and plays important roles in the consolidation of information from short-term memory to long-term memory and spatial navigation. Humans and other mammals have two hippocampi, one in...

 may result in the need for a specific type of learning requirement. A study was created to test this assumption in which the patients were trained to throw a bean bag at a target. It was found that the Alzheimer’s patients performed better on the task when learning occurred under constant training as opposed to variable. Also, it was found that gross motor memory in Alzheimer’s patients was the same as that of healthy adults when learning occurs under constant practice. This suggests that damage to the hippocampal system does not impair an Alzheimer’s patient from retaining new gross motor skills, implying that motor memory for gross motor skills is stored elsewhere in the brain.

Impairment

It is difficult to display cases of “pure” motor memory impairment because the memory system is so widespread throughout the brain that damage is not often isolated to one specific type of memory. Likewise, diseases commonly associated with motor deficits, such as Huntington's and Parkinson's disease
Parkinson's disease
Parkinson's disease is a degenerative disorder of the central nervous system...

, have a wide variety of symptoms and associated brain damage that make it impossible to pinpoint whether or not motor memory is in fact impaired. Case studies have provided some examples of how motor memory has been implemented in patients with brain damage.

Consolidation deficit

A recent issue in motor memory is whether or not it consolidates in a manner similar to declarative memory, a process that involves an initial fragile learning period that eventually becomes stable and less susceptible to damage over time. An example of stable motor memory consolidation in a patient with brain damage is the case of Clive Wearing
Clive Wearing
Clive Wearing is a British musicologist, conductor, and keyboardist suffering from an acute and long-lasting case of anterograde and retrograde amnesia, meaning that he lacks the ability to form new memories.-Musical career:...

. Clive has severe antrograde and retrograde amnesia due to damage in his temporal lobes, frontal lobes, and hippocampi, which prevents him from storing any new memories and making him aware of only the present moment. However, Clive still retains access to his procedural memories, to be specific, the motor memories involved in playing the piano. This could be because motor memory is demonstrated through savings over several trials of learning, whereas declarative memory is demonstrated through recall of a single item. This suggests that lesions in certain brain areas normally associated with declarative memory would not affect motor memory for a well-learned skill.

Dysgraphia for the alphabet

Case study: 54-year-old woman with known history of epilepsy

This patient was diagnosed with a pure form of dysgraphia
Dysgraphia
Dysgraphia is a deficiency in the ability to write primarily in terms of handwriting, but also in terms of coherence. It occurs regardless of the ability to read and is not due to intellectual impairment...

 of letters, meaning she had no other speech or reading impairments. Her impairment was specific to letters in the alphabet. She was able to copy letters from the alphabet, but she was not able to write these letters. She had previously been rated average on the Wechsler Adult Intelligence Scale
Wechsler Adult Intelligence Scale
The Wechsler Adult Intelligence Scale intelligence quotient tests are the primary clinical instruments used to measure adult and adolescent intelligence. The original WAIS was published in February 1955 by David Wechsler, as a revision of the Wechsler-Bellevue Intelligence Scale...

's vocabulary subtest for writing ability comparative to her age before her diagnosis. Her writing impairment consisted of difficulty remembering motor movements associated with the letters she was supposed to write. She 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 specific portion of the brain related to writing letters, which is dissociated from copying and drawing letter-like items.

See also

  • Procedural memory
    Procedural memory
    Procedural memory is memory for how to do things. Procedural memory guides the processes we perform and most frequently resides below the level of conscious awareness. When needed, procedural memories are automatically retrieved and utilized for the execution of the integrated procedures involved...

  • Motor learning
    Motor learning
    Motor learning is a “relatively permanent” change, resulting from practice or a novel experience, in the capability for responding...

  • Motor coordination
    Motor coordination
    thumb|right|Motor coordination is shown in this animated sequence by [[Eadweard Muybridge]] of himself throwing a diskMotor coordination is the combination of body movements created with the kinematic and kinetic parameters that result in intended actions. Such movements usually smoothly and...

  • Muscle
    Muscle
    Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...

  • Memory consolidation
    Memory consolidation
    Memory consolidation is a category of processes that stabilize a memory trace after the initial acquisition. Consolidation is distinguished into two specific processes, synaptic consolidation, which occurs within the first few hours after learning, and system consolidation, where...

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