This goal of this blog post is to present an argument against how an area of study I have claimed to hold expertise in is currently defined, that area being motor control.
First, let me begin by acknowledging we often take for granted that all our motor actions could not be performed without sensory feedback. From being able to stand up, walk about, or pick up that lovely pint of guinness without spilling a drop, feedback predominantly from our visual, vestibular and somatosensory systems informs us about the success of our own actions and their effects on the environment around us. A perfect example to help illustrate the importance of sensory feedback for controlling our movements can be seen in patient Ian Waterman (IW). IW had a viral infection eliminated his somatosensory feedback from the neck down. As a result, IW received no information about the consequences of contracting any of his muscles for movement, he felt nothing he came into contact with and also had no sense of proprioception (unconscious awareness of the position and movement of one’s limbs and body in space). This made even the simplest of tasks, like sitting up in bed, seem like a serious chore (more of the obstacles that IW faced can be seen by going to the following link – https://www.youtube.com/watch?v=FKxyJfE831Q). It is from special cases like patient IW that we can better appreciate the vital importance of studying the role of sensory feedback for controlling human movement.
One area that has proven to be advantageous for studying motor control is the area of sports performance. In most sports, success is often dictated by the participant’s ability to perform complex motor actions accurately and consistently. As you may be convinced of above, this makes the role of precise and accurate sensory feedback in sport performance highly essential. But how is sensory feedback used to control the accuracy and consistency of complex motor patterns? It is all related to how the brain learns and adapts new motor patterns. In a nutshell, whenever we tell our body to do something (like reach out to grab that delicious pint of guinness – thirsty yet?) our central nervous system (CNS) initiates a neural cascade that travels eventually from our motor cortex down to the muscles of our arm to cause them to contract in such a way that we reach out. However, at the same time, the CNS also sends out a signal that represents the expected sensory consequences of what is assumed to be a successful motor action. This signal is termed the ‘efference copy’. As we begin to reach out, online feedback from the stretch of our muscles, skin etc., travels back up to the brain and is compared with the ‘efference copy’ of expected sensory feedback. If the actual feedback matches up with the expected, our action is deemed successful.
However if there is a mis-match, the difference (error signal) is what is used to update our motor pattern for the next time we perform the task (see eq 1).
Eq. 1: (Actual Sensory Feedback – Efference Copy = Error)
Based on this, one would assume that understanding how sensory feedback is used to control motor actions might allow one to better utilize feedback during training and thus enhance performance. Moreover, better awareness of the sensory consequences of our actions in sport can also help reduce the likelihood of injury. However, far too often, athletes can become too focused on the ‘motor’ aspects of their technique during training without allocating enough attention on the appropriate error feedback they receive from their movements. As a result, skill acquisition may take longer and movement patterns may not be as efficient. This brings me back to the topic of ‘motor-control’. Being described as ‘the process by which humans and animals use their brain/cognition to activate and coordinate the muscles and limbs involved in the performance of a motor skill’, ‘motor control’ in the realm of neurophysiology research is all too often solely used to describe how motor actions are initiated. Although this question deserves attention, it has nothing to do with control, as for one to be able to control their motor actions, they must, as I hopefully have convinced you above, use feedback about the intended success of those actions. Therefore, I caution the use of the term ‘motor control’ and rather propose that the more all-encompassing term, ‘sensory-motor control’ is implemented to describe the process by which motor actions are initiated, coordinated and controlled to improve balance and movement during physical endeavours.
Dr Adam Toth is a post-doctoral researcher with LERO and the Department of Physical Education and Sports Sciences at the University of Limerick. His current research involves the investigation of key neuropsychological and neurophysiological performance indicators in elite eSports gamers. His other research interests include the examination of sensorimotor control of the golf swing and psychological indicators of performance in elite and amateur golfers. You can contact Adam by email at firstname.lastname@example.org view his profile on Linked In or see his research profile on Researchgate.