Behavioral and Electrophysiological Evidence of Motor Cortex Activation Related to an Amputated Limb: A Multisensorial Approach

Abstract

Phantom limb sensations may be linked to motor activities in the deafferented cortices of amputees, with artificial visual feedback of an amputated limb leading to enhanced phantom sensations. The present study was designed to verify if cortical motor activity related to an amputated limb can be triggered by visual input using an objective behavioral measure and with a neurophysiological correlate. Trauma amputees and normally limbed subjects showed superior performance in a mirror-drawing task when the mirror was placed sagittally (giving visual feedback of the amputated/inactive limb) compared with when it was placed frontally. Measurement of lateralized movement-related brain potentials showed that, under the lateral mirror condition, contralateral motor activity of the viewed hand was observed in both normal subjects and trauma amputees. In contrast, this activity was not observed in subjects with congenital limb absence. These findings suggest that, in traumatic amputees, motor enhancement due to visualization of the movements of the missing limb reflects the effectiveness of motor commands to the missing limb, strengthening the hypothesis of the functional survival of deafferented cortical motor areas.

Perception of hand movement by mirror reflection evokes brain activation in the motor cortex contralateral to a non-moving hand

“…As with the findings of Praamstra et al (2011), our findings are not consistent with those of Touzalin-Chretien & Dufour (2008), Touzalin-Chretien et al (2009, 2010. Ipsilateral amplitude in the mirror view conditions was clearly larger in the present study in comparison to ipsilateral amplitude in direct view conditions.…”

“…However, ERP data of the present study consistently showed larger amplitude at electrode sites contralateral to the movement hand compared to the amplitude at electrode sites ipsilateral to the movement hand in both experimental conditions. We, therefore, agree with Praamstra et al (2011) that MVF induces additional excitation in the ipsilateral M1 of the moving hand but contrary to Touzalin-Chretien & Dufour (2008), Touzalin-Chretien et al (2009, 2010 this additional excitation does not exceed the contralateral activation.…”

“…Along those lines, TouzalinChretien and colleagues measured the lateralized readiness potential (LRP) to assess motor readiness of movement as a marker of M1 activation. Results revealed evidence of an LRP associated with the resting hand in the mirror view condition (Touzalin-Chretien & Dufour, 2008;Touzalin-Chretien, Ehrler, & Dufour, 2009, 2010. However, the findings of TouzalinChretien et al were refuted by Praamstra, Torney, Rawle, and Miall (2011) with the claim that there was a methodological error in computation of the LRP in the mirror view conditions.…”

Misconceptions about Mirror-Induced Motor Cortex Activation

“…In 3 recent publications, Touzalin-Chretien and Dufour (2008) and Touzalin-Chretien et al (2009, 2010) used the lateralized readiness potential (LRP) to investigate motor cortex activation induced by mirror visual feedback. Using a mirror placed in the midsagittal plane in front of the participant, the investigators had participants look at movements of their right hand as if it was their left hand.…”

Phantom limb pain and bodily awareness

“…One randomized controlled trial showed significant treatment effects of mirror therapy [90]; however, there is limited systematic evidence [91], and the paradigm appears to be counterproductive during early rehabilitation [92]. Pre-existing body representations or maladaptive cortical reorganization may impede the efficacy of this therapy considering, in a once-off treatment, congenital amputees [93], and those with chronic phantom pain [94 ] do not activate contralateral sensory and motor cortices during mirror visual therapy. Anecdotally, mirror therapy may restore 'normal' phantom limb perception or posture, for example, one patient was able to 'release' a metal bar that was felt to restrict phantom limb movement [95].…”