The technique of mirror therapy was introduced by Dr. Ramachandran and it can be applied to the rehabilitation of phantom limb patients by improving physical movements. The illusion of movement in the affected body part and leads to muscle activity in the inactive phantom limb along with activity in the brain associated with that body part (Arya 2016). This is due to the role of mirror neurons, cells in the premotor cortex and inferior parietal lobule, which are stimulated when observing and physically conducting an action (Arya 2016).
Mirror neurons help reorganize neurons in the damaged motor-cortex area of a patient since they have the ability to mirror observed motor actions in the brain. The purpose of this essay is to determine whether observing, through the action of mirror neurons can help one learn a motor task or is physically practicing the task the only way? In other words, can imagining movement replace the physical act of performing it? A study by Allami et al. wanted to determine whether movement time (MT) in milliseconds through mental rehearsal gave the same results as physical practice and what ratio of physical execution and rehearsal is optimal learning.
Twenty five right-handed participants in this study were asked to grasp an object and place it into its designated slot as fast as they could in 240 trials by each group. The G0 group performed only through physical practice, G25 rehearsed for 60 trails and physically performed 180 times, G50 rehearsed 120 times and performed 120 times, and G75 rehearsed for 180 trails and performed physically of 60 trials. The MT was measured by the time first movement (MT1), reaching and grasping the object, and second movement (MT2), the insertion of the object in the slot.
The position of the object varied from trail to trail. In the motor imagery test participants could only imagine or feel themselves doing the task. The MT of the first trial showed that subjects in groups G50 and G75, with a larger rehearsal component, were faster than G0 and G25. The results implied that mental rehearsal strengthens brain networks involved in sensory motor control. This study helped understand the role of observation in motor learning as it showed that different rates of imagery lead to different rates of learning.
The limitations are the differences between the groups before training, the small size of the groups, the simplicity of the task and whether 240 trails are enough practice to learn the task. The study by Frank et al. wanted to determine if motor changes would be noticeable by perceptual changes through mental representations. Forty five university students were participants in the study and had no previous experience with golf. They were assigned to three groups: combined mental and physical practice, only physical practice and no practice.
They were asked putt a golf ball to a target placed three meters from the start point, and the distance th ball travelled was measured. The participants were asked to rest for three days following the test after which they would be tested again to see if they had acquired the skill. They found that long term memory of golf putting resulted from learning by motor action, yet mental practice combined with physical enhanced the development of the skill rather than only physical practice. Permanent changes in putting result from practice of executing a motor skill.
A limitation of this study is the combined group practicing mentally in addition to the physical practice, practiced twice the amount of trials (30 executed and 30 imagined) than the physical practice group (30 executed putts/ practice session). Differences found between the two practice groups might be due to the difference in amount of practice and not to mental practice itself. The strength of this study was that the researchers took into account the variations in imagining the task by administrating a questionnaire which asked the participants to rate the ease or difficulty of imagining movements.
Mental rehearsal for 120 trails in the G50 group showed a faster MT2 movement which suggests mental rehearsal is important for learning to take place. It also implies that mental rehearsal for more than 120 trials is enough to reach the same performance outcome as 240 trails of physical practice alone. The G0 group reached a plateau of performance suggesting that only physical movement does not lead to improvements in MT. The MT of the first trial showed that subjects in groups G50 and G75 were faster than G0 and G25. In the last trail, differences in the MTs in groups G50 and G75 compared to G0 were not as different.
However there was a difference between groups G75 and G25 for the last trial suggesting that mental rehearsal is better than no practice at all. The results also imply that mental rehearsal strengthens brain networks involved in sensory motor control thereby making learning by physical practice more effective. The study by Frank et al. showed the effect of physical practice was greater than that of mental since the group with only physical activity could perform the task better after three days of rest. Additional mental practice was not effective in enhancing motor performance.
However, extending the practice phase of trials may have an effect on additional mental practice. Mental practice can promote structural development by affecting the perceptual-cognitive level during early motor learning but it may not transfer to the motor output level. This implies that mental practice operates primarily on higher levels within the motor action system during early skill acquisition. They found that long term memory of golf putting resulted from learning by motor action, yet mental practice combined with physical enhanced the development of the skill rather than only physical practice.
The researchers concluded that additional mental practice has a smaller effect on putting than physical practice due to its smaller effect in magnitude as compared to the effect of physical practice. In conclusion, mental representation is shown to enhance the acquisition of a motor skill yet it cannot replace the physical practice, since mental imaging may take more time to influence the acquisition of the skill as compared to the physical act.
Mirror neurons are important for higher level processing such as visualizing and action comprehension; however physical practice is the most effective way to learn a task. Motor production and mental representations have a mutual influence on each other, suggesting there is an overlap between our observed, imagined and produced movements which beckons the question as to how we control our actions (Carvalho 2013).