Motor Control and Feedback (Part 2)
April 10th 2011 04:59
Feedback in Motor Learning
Feedback is information arising as a consequence of performance (van Dijk, 2006). It provides basis for evaluation of correctness of movement or task. Recalling what was discussed earlier about the neurologic control of learning, feedback can be a tool that enables the learner to identify the objective of the task at hand.
According to Thorpe (2003), this is an important element for motor learning. And for this she briefly, but clearly gave accounts on the two main types of feedback: the intrinsic and the extrinsic feedback. Thorpe differentiated these two types of feedback. She emphasized that intrinsic feedback is a type which is provided to the performer by the sensory systems (visual, auditory, proprioceptive, vestibular, and cutaneous) as a result of movement. On the other hand, extrinsic feedback, also known as augmented feedback is supplemental information given to the performer about the task. Unlike the intrinsic type, it originates from an external source, such as biofeedback, videotape, and verbal or tactile cues.
Going back to van Dijk’s works, he termed the intrinsic feedback as inherent feedback. The reason for this is that inherent feedback originates from the sensory information that is a natural part of performing a skill. In other words, it is a feedback which is given by a performer to his self. On the other hand, van Dijk also introduced the term artificial feedback when referring to augmented or extrinsic type of feedback. He also stated that the adjective "augmented" refers to adding to or enhancing task-intrinsic feedback with an external source (e.g. training devices).
Upon knowing the differences between the two, we now have to deal with these important questions. Which learner and task require intrinsic feedback? Which require augmented feedback?
Thorpe explains that when intrinsic feedback is not available, critical task requirements are not clear, or the learner is not familiar with the relationship between the goal and required movement, augmented feedback is necessary. Conversely, learning can be inhibited by augmented feedback if the movement provides enough intrinsic feedback to influence behavior.
If we are to interpret Thorpe’s statement, in order to fit the rehabilitation setting, we shall see that augmented feedback can be used if the following conditions are satisfied: unseen targets, disabilities like loss of sensation, or misunderstood intrinsic feedback. So that, if a patient with right hemiplegia is about to start gait training with the use of a cane on his left side, surely we cannot rely on intrinsic feedback in facilitation of learning. Why? This patient suffers with weakness and sensory loss. Even his visual acuity is questionable. And it is probable that this patient do not have any idea about the requirements to carry out the task. This is when our role as physical therapists comes into play. We give this kind of patient visual or tactile cues, verbal coaching, and even record practice sessions, and having him watch his own performance afterwards.
When do we withdraw from using augmented feedback? If sensory or intrinsic feedback is available, understood, and usable, we might as well give less focus in providing augmented feedback. If an individual has intact senses, the target is seen, and/or his level of proficiency is advanced or expert, most of the time there is no use for feedback from external sources. It would only duplicate information that is already available, making it redundant. So if we say to an individual performing reaching exercises that “you reached it”, when the person obviously sees that, it becomes inappropriate and annoying.
Choice of feedback type is also age-dependent. The ability to process intrinsic information may be compromised due to age related changes in information processing or to cognitive/ sensory deficit in certain patient groups. This is true among elderly whose reflexes become slow, muscles become weak, and cognitive-sensory processing becomes poor (Zucker, 2003). In these circumstances these people may be more dependent on augmented feedback to learn motor skills compared to young, healthy adults (van Dijk, 2006).
Even in pediatric cases, feedback is proven beneficial in a child’s capability to learn. Obviously, the feedback of choice is augmented feedback. Hypotheses by Valvano and Carollo (2003) stated that augmented feedback in the form of manual guidance enhances practice in the early phase of learning a novel motor skill. Their basis for such is concepts from Gentile and Newell, stating that the early stages of learning include a learner’s discovery of the conditions that must be met in order to be successful with the task. A child cannot do this alone. And we, in the rehabilitation team, should be the ones providing tactile cues and guidance on the specific part we want a child to utilize in performing the task (manual guidance on the trunk if we are to teach sitting).
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