Different effects of the mirror illusion on motor and somatosensory processing.
OBJECTIVE
Mirror therapy can improve motor and sensory functions, but effects of the mirror illusion on primary motor and somatosensory cortex could not be established consistently.


METHODS
Fifteen right handed healthy volunteers performed or observed a finger-thumb opposition task. Cerebral activations during normal movement (NOR), mirrored movement (MIR) and movement observation (OBS) by means of a video chain were recorded with functional magnetic resonance imaging (fMRI). Activation sizes in movement > static conditions were identified using SPM8 (p < 0.001, unc.) and attributed to predefined areas employing the Anatomy toolbox 1.8. Laterality indices for the responsive areas were calculated on the basis of the number of activated voxels.


RESULTS
Relevant bilateral BOLD responses were found in primary motor (M1) and somatosensory (S1 - BA 2, 3b and 3a) cortex, premotor and parietal areas and V5. When comparing MIR to NOR, no significant change of contralateral activation in M1 was found, but clearly at S1 with differences between hands.


CONCLUSIONS
The mirror illusion does not elicit immediate changes in motor areas, yet there is a direct effect on somatosensory areas, especially for left hand movements. These results suggest different effects of mirror therapy on processing and rehabilitation of motor and sensory function.
MEDIAN Klinik Berlin-Kladow, Berlin, Germany Centre for Stroke Research Berlin, Charité - University Medicine Berlin, Berlin, Germany.
Claire
C
Fritzsch
MEDIAN Klinik Berlin-Kladow, Berlin, Germany Department of Neurology, Charité - University Medicine Berlin, Berlin, Germany Centre of Rehabilitation, the Second Affiliated Hospital of Jiaxing University, Jiaxing, China.
Jing
J
Wang
MEDIAN Klinik Berlin-Kladow, Berlin, Germany Centre for Stroke Research Berlin, Charité - University Medicine Berlin, Berlin, Germany.
Luara Ferreira
LF
Dos Santos
MEDIAN Klinik Berlin-Kladow, Berlin, Germany Department of Neurology, Charité - University Medicine Berlin, Berlin, Germany.
Karl-Heinz
KH
Mauritz
MEDIAN Klinik Berlin-Kladow, Berlin, Germany Centre for Stroke Research Berlin, Charité - University Medicine Berlin, Berlin, Germany.
Maddalena
M
Brunetti
MEDIAN Klinik Berlin-Kladow, Berlin, Germany Centre for Stroke Research Berlin, Charité - University Medicine Berlin, Berlin, Germany Centre for Rehabilitation Science, University Potsdam, Potsdam, Germany.
Christian
C
Dohle
D000328:Adult; D001931:Brain Mapping; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006225:Hand / Q000502:physiology; D006801:Humans; D007088:Illusions; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology; D013003:Somatosensory Cortex / Q000502:physiology*; D055815:Young Adult
Movement; laterality; mirror; sensorimotor cortex; stroke