Brain Advance Access originally published online on November 7, 2003
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Brain, Vol. 127, No. 1, 120-132, 2004
© 2004 Guarantors of Brain
doi: 10.1093/brain/awh006
Left and right hand recognition in upper limb amputees
1 Dipartimento di Psicologia, Università ‘La Sapienza’, 2 IRCCS Fondazione S.Lucia, Roma, Italy, 3 Institut de Sciences Cognitive, Bron, 4 Hôpital des Massues, Lyon, France and 5 Research Imaging Center, UTHSCSA, San Antonio, Texas, USA
Correspondence to: Angela Sirigu, Institute des Sciences Cognitives, 67, Blv. Pinel, 69675 Bron, France E-mail: sirigu{at}isc.cnrs.fr
Previous research suggests a close similarity in brain activity between mental simulation of a movement and its real counterpart. To explore this similarity, we aimed to assess whether imagery is affected by the loss of a limb or of its motor skills. We examined the performance of 16 adult, upper limb amputees (and age-matched controls) in a left/right hand judgement task that implicitly requires motor imagery. The experimental group included subjects who had suffered the amputation of the dominant or the non-dominant limb. Although responding well above chance, amputees as a group were slower and less accurate than controls. Nevertheless, their response pattern was similar to that of controls, namely slower response times and more errors for stimuli depicting hands in unnatural orientations, i.e. postures difficult to reach with a real movement. Interestingly, for all stimuli, amputees’ performance was strongly affected by the side of limb loss: subjects who underwent amputation of their preferred limb made more errors and required greater latencies to respond as compared with amputees of the non-dominant limb. In a further analysis we observed that the habit of wearing an aesthetic prosthesis significantly interfered with the ability to judge the corresponding hand. Our data lead to three main conclusions: (i) loss of a single limb per se does not prevent motor imagery but it significantly enhances its difficulty; (ii) these subjects apparently perform the hand recognition task using a strategy in which they initially mentally simulate movements of their dominant limb; (iii) wearing a prosthesis, devoid of any motor function, seems to interfere with motor imagery, consistent with the view that only ‘tools’ can be incorporated in a dynamic body schema.
Key Words: hand recognition; amputation; motor imagery; hand preference; prosthesis
Abbreviations: ANOVA = analysis of variance; DP– = loss of dominant limb/not wearing prosthesis; DP+ = loss of dominant limb/wearing prosthesis; NDP– = loss of non-dominant limb/not wearing prosthesis; NDP+ = loss of non-dominant limb/wearing prosthesis; RT = response time
Received April 24, 2003. Revised July 31, 2003. Accepted August 1, 2003.
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