Motor Control and Motivation

Since my systematic review will be looking at how gaming and/or virtual reality impact motor control and motivation, I did a bit of reading on both motor control and motivation today. Hopefully the stuff below is actually accurate and is not just me misinterpreting the articles I've read. (As with previous posts, I've put references at the bottom so you can read the original stuff if you don't trust me.)

Motor Control

Unlike robots, which send the same commands to their motors, human motor commands are highly variable and context-dependent. For example, we might need to adjust to factors such as fatigue, pain, carrying heavy objects, and so on. One model suggests that we have two systems of information for estimating our body state and adjusting accordingly: firstly, our brain can predict what should happen, and secondly, our sensory system reports what is actually happening. These two systems may be integrated and their relative importance optimally weighted in order to help us predict our body state and improve our motor control.

But why have two systems? you may ask. What's wrong with just having one and sticking to it? The long and short of it is that it's a trade-off between speed and accuracy. Sensory feedback is important because it tells us what is actually happening. However, there are delays inherent in feedback, which can lead to instability (see here). Using our brain to predict sensory feedback can mostly eliminate such instability. The cerebellum can predict the state of our limbs from the history of motor commands. It can also use an efferent copy of a motor command to predict its consequences and correct said motor command, if necessary.

In another hypothesis of motor adaptation, reflex pathways can in themselves act as a "teaching signal" for the brain. That is, to my understanding, our brain can "learn" the corrected response. However, experiments suggest that motor adaptation is due to error signals (visuomotor cues etc.) rather than due to error corrections (i.e. reflex responses).

Motor Rehabilitation

The motor control systems described above and the resulting "predictive control" are important in adapting our movements to make them seamless and efficient. However, in cerebral palsy, there are deficits in movement execution, movement representation and movement planning. Such deficits may result in poor motor imagery (i.e. the ability to imagine the movements that you need to carry out), as the neural networks for motor imagery and predictive control have been found to overlap.

In motor rehabilitation, it is important that patients can use feedback to compare executed versus the intended actions. If the ability to do so is compromised, even sheer repetition of skills may not result in any improvement. In cerebral palsy, sensory information may be compromised, which in turn leads to issues in implementation of error correction and predictive control. As such, motor rehabilitation should take into account methods of augmented (multisensory extrinsic) feedback and techniques that cue attentional focus.

Augmented feedback provides feedback above and beyond naturally-occurring intrinsic feedback. Augmented feedback can include knowledge of results (information about the outcome of a movement, for example percentage of successes), knowledge of performance (information about the manner in which the movement was performed and its form) and concurrent augmented feedback (real-time feedback that may be visual, kinaesthetic or auditory). Concurrent augmented feedback can aid in the development of coordination, leading to enhanced stability.

In attentional training, external cues encourage the patient to focus on the effects of the movement, rather than the movement itself. Such an external focus allows the patient to enlist rapid control processes, including the ability to implement adjustments. An internal focus, on the other hand, might encourage a focus on the self and on self-evaluation, which might interfere with the unconscious flow of skilled performance. Attentional training has been found to increase performance on retention and transfer tasks, as actions are most efficient when planned according to intended outcomes.

Motivation

Tatla et al. (2013) defined motivation as "an energy and drive function that causes an individual to move toward satisfying specific needs and general goals in a persistent manner." It is thought to be a critical modulator of functional plasticity, leading to improved motor and functional outcomes. A systematic review by Tatla et al. (2013) found that combining a motivating intervention with therapy instruction resulted in a greater level of biofeedback as compared to therapy alone. The type of motivating intervention also mattered: virtual reality resulted in more biofeedback than watching a DVD. If games were used as a motivator, the type of game was also important. However, some studies found a possible decline in intensity and initiative to play over time.

Another interesting point that was brought up in the Tatla et al. (2013) systematic review is that children with cerebral palsy have lower levels of motivation as compared to their typically developing peers. Important factors that correlate with motivation include self-efficacy and competence. Improvements in motor ability, self-care, communication and socialisation may help to increase motivation in this population.

References

Shadmehr, R, Smith, MA, Krakauer, JW 2010, 'Error Correction, Sensory Prediction, and Adaptation in Motor Control', Annual Review of Neuroscience, vol. 33, pp. 89-108.

Tatla, SK, Sauve, K, Virji-Babul, N, Holsti, L, Butler, C, Loos, HFM 2013, 'Evidence for outcomes of motivational rehabilitation interventions for children and adolescents with cerebral palsy: an American Academy for Cerebral Palsy and Developmental Medicine systematic review', Developmental Medicine and Child Neurology, vol. 55, no. 7, pp. 593-601.

Wilson, Peter 2014, 'Developmental cognitive neuroscience perspective on motor rehabilitation: The case for virtual reality-augmented therapy', International Journal of Child Health and Human Development, vol. 7, no. 4, pp. 341-348.