Intereference of phantom limb perception with motor imagery after unilateral upper-limb amputation
Phantom pain is the sensation in the organ that is amputed or missing but is still attached to the body and is moving appropriately with the other body parts. Although not all the phantom limb pains are painful, but sometimes gesturing, itchiness can also be experienced. To overcome this, sometimes motor imagery is used.
Motor imagery is the dynamic state during which an individual mentally simulates a given action. A potential contributor to impaired motor imagery in amputees is an alteration of the body schema as a result of the presence of a phantom limb. However, nature of the relationship between motor imagery and phantom experiences remains unknown.
A study was conducted to observe the influence of phantom limb perception on motor imagery using a hand mental rotation task by means of behavioral and electrophysiological measures. Healthy controls were compared with the amputees who perceived a phantom limb during the task. All the healthy controls (HC) and amputees successfully completed the task.
In this study, event related desynchronization of EEG in the beta band in central and parietal areas showed an angular disparity specifically in amputees with phantom limb perception. Significantly positively correlated phantom vividness were observed with positive beta-ERD values. From the analysis, it was evaluated that phantom limb perception was an important interferential factor for motor imagery after amputation and the interference represents an unnatural posture of the phantom limb. Dominant limb amputees suffered more impairments in motor imagery than those who lost their non-dominant limb. Phantom experiences should be taken into consideration when studying motor imagery in amputees.