Motor imagery in right hemiparesis is dependent on posture congruency

In a recent study it was shown that the ability to use motor imagery was compromised in right congenital hemiparesis, viz. left hemisphere damage (Mutsaarts et al., 2006). However, posture of the displayed stimuli and the actual posture of the hand making the response were incongruent in that study. Ample evidence exists that such an incongruency negatively influences laterality judgements in a motor imagery task, which may have affected the findings in the Mutsaarts et al. (2006) study. In the present study, three participant groups (controls participants, participants with left hemiparesis, and participants with right hemiparesis [all n=11]) were engaged in a motor imagery task in which the posture of the displayed drawings of the hands and the posture of the hand of the participant making the response were congruent. It was hypothesised that this postural congruency would facilitate motor imagery in participants with right hemiparesis. Participants had to make laterality judgments as quickly as possible upon appearance of the rotated stimuli (i.e., hands) on a screen. The results showed significant linear effects of rotation angle on reaction times for all three groups. In addition, the number of errors made was far below chance level. These findings suggests that motor imagery in right hemiparesis is still intact, but is critically dependent on the congruency between posture of the stimulus and posture of the hand making the response. Furthermore, the influence of hand posture on motor imagery shows that motor imagery is an embodied cognitive process. Reference Mutsaarts, M., Steenbergen, B., & Bekkering, H. (2006). Impaired motor imagery in right hemiparetic cerebral palsy. Neuropsychologia, 45(4), 853-9.