Cortical responses to the mirror box illusion: a high-resolution EEG study.
The mirror box illusion has proven a helpful therapy in pathologies such as phantom limb pain, and although the effect has been suggested to be a result of the interaction between pain, vision, touch, and proprioception, the mechanisms are still unknown. Multichannel (124) brain responses were investigated in healthy men (N = 11) and women (N = 14) during the mirror box illusion. Tactile somatosensory evoked potentials were recorded from the right thumb during two control conditions and two illusions: (control 1) no mirror: looking at the physical right thumb during stimulation, (control 2) no mirror: looking at the physical left thumb during stimulation, (illusion 1) mirror: the illusion that both thumbs were stimulated, and (illusion 2) mirror: the illusion that none of the thumbs were stimulated. In men, a significant medial shift in the y coordinate of the N70 dipole in illusion 2 (P = 0.021) was found when compared with illusion 1. No dipole shift was found for women. Additionally, men showed higher prevalence of P180 cingulate cortex activation during illusion 2 when compared with control 1 and 2 (P = 0.002). During illusion 2, the degree of conformity with the statement "The hand in the mirror feels like my other hand" was negatively correlated with the N70 x coordinate for men and positively correlated with the N70 z coordinate for women. In conclusion, short-term cortical plasticity can be induced by a mismatch between visual input and location of tactile stimulation in men. The present study suggests that gender differences exist in the perception of the mirror box illusion.
Department of Health Science and Technology, Center for Sensory Motor Interaction, Faculty of Medicine, Aalborg University, Frederik Bajers Vej 7A, 9220 Aalborg East, Denmark.
Line Lindhardt
LL
Egsgaard
Laura
L
Petrini
Giselle
G
Christoffersen
Lars
L
Arendt-Nielsen
D000328:Adult; D002540:Cerebral Cortex / Q000502:physiology*; D004569:Electroencephalography / Q000379:methods; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D007088:Illusions / Q000502:physiology*; D008297:Male; D010775:Photic Stimulation / Q000379:methods; D010812:Physical Stimulation / Q000295:instrumentation / Q000379:methods; D012727:Sex Characteristics; D055698:Touch Perception / Q000502:physiology*