Motor learning

Motor learning refers broadly to changes in an organism's movements that reflect changes in the structure and function of the nervous system. Motor learning occurs over varying timescales and degrees of complexity: humans learn to walk or talk over the course of years, but continue to adjust to changes in height, weight, strength etc. over their lifetimes. Motor learning enables animals to gain new skills, and improves the smoothness and accuracy of movements, in some cases by calibrating simple movements like reflexes. Motor learning research often considers variables that contribute to motor program formation (i.e., underlying skilled motor behaviour), sensitivity of error-detection processes,^[1][2] and strength of movement schemas (see motor program). Motor learning is "relatively permanent", as the capability to respond appropriately is acquired and retained. Temporary gains in performance during practice or in response to some perturbation are often termed motor adaptation, a transient form of learning. Neuroscience research on motor learning is concerned with which parts of the brain and spinal cord represent movements and motor programs and how the nervous system processes feedback to change the connectivity and synaptic strengths. At the behavioral level, research focuses on the design and effect of the main components driving motor learning, i.e. the structure of practice and the feedback. The timing and organization of practice can influence information retention, e.g. how tasks can be subdivided and practiced (also see varied practice), and the precise form of feedback can influence preparation, anticipation, and guidance of movement.

Behavioural approach

Structure of practice and contextual interference

Contextual interference was originally defined as "function interference in learning responsible for memory improvement".^[3] Contextual interference effect is "the effect on learning of the degree of functional interference found in a practice situation when several tasks must be learned and are practiced together".^[4] Variability of practice (or varied practice) is an important component to contextual interference, as it places task variations within learning. Although varied practice may lead to poor performance throughout the acquisition phase, it is important for the development of the schemata, which is responsible for the assembly and improved retention and transfer of motor learning.^[3][5]

Despite the improvements in performance seen across a range of studies, one limitation of the contextual interference effect is the uncertainty with regard to the cause of performance improvements as so many variables are constantly manipulated. In a review of literature,^[3] the authors identify that there were few patterns to explain the improvements in experiments that use the contextual interference paradigm. Although there were no patterns in the literature, common areas and limitations that justified interference effects were identified:^[3]

1. Although the skills being learned required whole-body movements, most tasks had a common feature; they all contained components that could be isolated.
2. Most of the studies supporting interference effect used slow movements that enabled movement adjustments during movement execution.
3. According to some authors bilateral transfer may be elicited through alternate practice conditions, as a source of information can develop from both sides of the body. Despite improvements seen in these studies, interference effects would not be attributed to their improvements, and it would have been a coincidence of task characteristics and schedule of practice.^[3][6]
4. The terminology of "complex skills" has not been well defined. Procedural manipulations, which vary between experiments (e.g., changing the similarity between tasks) has been cited as a contributor to skill complexity.

Feedback given during practice

Several studies have manipulated the presentation features of feedback information (e.g., frequency, delay, interpolated activities, and precision) in order to determine the optimal conditions for learning. See Figure 4, Figure 6, and summary Table 1^[8] for a detailed explanation of feedback manipulation and knowledge of results (see below).

Knowledge of performance

Knowledge of performance (KP) or kinematic feedback refers to information provided to a performer, indicating the quality or patterning of their movement.^[7] It may include information such as displacement, velocity or joint motion. KP tends to be distinct from intrinsic feedback and more useful in real-world tasks. It is a strategy often employed by coaches or rehabilitation practitioners.

Knowledge of results

Knowledge of results (KR) is defined as extrinsic or augmented information provided to a performer after a response, indicating the success of their actions with regard to an environmental goal.^[8] KR may be redundant with intrinsic feedback, especially in real-world scenarios.^[7] However, in experimental studies, it refers to information provided over and above those sources of feedback that are naturally received when a response is made (i.e., response-produced feedback;^[1][9][10] Typically, KR is also verbal or verbalizable.^[11] The impact of KR on motor learning has been well-studied and some implications are described below.

Experimental design and knowledge of results

Often, experimenters fail to separate the relatively permanent aspect of change in the capability for responding (i.e. indicative of learning) from transient effects (i.e. indicative of performance). In order to account for this, transfer designs have been created which involve two distinct phases.^[11] To visualize the transfer design, imagine a 4x4 grid. The column headings may be titled "Experiment #1" and "Experiment #2" and indicate the conditions you wish to compare. The row headings are titled "Acquisition" and "Transfer" whereby:

1. The acquisition block (2 columns) contains the test conditions in which some variable is manipulated (i.e. different levels of KR applied) and different groups receive different treatments. This block represents the transient effects of KR (i.e. performance)
2. The transfer block (2 columns) contains the test conditions in which that variable is held constant (i.e. a common level of KR applied; normally a no-KR condition). When presented with a no-KR condition, this block represents the persistent effects of KR (i.e. learning). Conversely, if this block is given to subjects in a format where KR is available, transient and persistent effects of KR are convoluted and it is argued not interpretable for learning effects.

After a rest period, the change in the capability for responding (i.e. effects) are argued to be those attributed to learning, and the group with the most effective performance has learned the most.

Functional role of knowledge of results and potential confounding of effects

KR seems to have many different roles, some of which can be viewed as temporary or transient (i.e. performance effects). Three of these roles include: 1) motivation, 2) associative function, and 3) guidance. The motivational influence can increase the effort and interest of the performer in the task as well as maintain this interest once KR is removed.

The specificity of learning hypothesis suggests that learning is most effective when practice sessions include environment and movement conditions which closely resemble those required during performance of the task — replicating the target skill level and context for performance.[7]^p. 194 It suggests that the benefit of specificity in practice occurs because motor learning is combined with physical practice during the learned sport or skill.^[14]p. 90 Contrary to previous beliefs, skill learning is accomplished by alternating motor learning and physical performance, making the sources of feedback work together. The learning process, especially for a difficult task, results in the creation of a representation of the task where all relevant information pertaining to task performance is integrated. This representation becomes tightly coupled with increasing experience performing the task. As a result, removing or adding a significant source of information after a practice period where it was present or not, does not cause performance to deteriorate. Alternating motor learning and physical practice can ultimately lead to a great, if not better performance as opposed to just physical practice.

Physiological approach

The

Impairments associated with developmental coordination disorder (DCD) involve difficulty in learning new motor skills as well as limited postural control and deficits in sensorimotor coordination.^[17] It appears that children with DCD are not able to improve performance of complex motor tasks by practice alone.^[18] However, there is evidence that task-specific training can improve performance of simpler tasks.^[19] Impaired skills learning may be correlated with brain activity, particularly, a reduction of brain activity in regions associated with skilled motor practice.^[20]

Apraxia

Motor learning has been applied to stroke recovery and neurorehabilitation, as rehabilitation is generally a process of relearning lost skills through practice and/or training.

• Apraxia
• Bayesian inference in motor learning
• Brain–computer interface
• Cephalocaudal and proximodistal trends
• Cognitive science
• Motor skill
• Motor coordination
• Muscle memory
• Procedural memory
• Sequence learning

References