TY - JOUR
T1 - Enhanced corticospinal response to observed pain in pain synesthetes
AU - Fitzgibbon, Bernadette M.
AU - Enticott, Peter G.
AU - Bradshaw, John L.
AU - Giummarra, Melita J.
AU - Chou, Michael
AU - Georgiou-Karistianis, Nellie
AU - Fitzgerald, Paul B.
PY - 2012
Y1 - 2012
N2 - Observing noxious injury to another's hand is known to induce corticospinal inhibition that can be measured in the observer's corresponding muscle. Here, we investigated whether acquired pain synesthetes, individuals who experience actual pain when observing injury to another, demonstrate less corticospinal inhibition than do controls during pain observation, as a potential mechanism for the experience of vicarious pain. We recorded motor-evoked potentials (MEPs) induced at two time points through transcranial magnetic stimulation while participants observed videos of a hand at rest, a hypodermic needle penetrating the skin, a Q-tip touching the skin, and a hypodermic needle penetrating an apple. We compared MEPs in three groups: 7 amputees who experience pain synesthesia, 11 nonsynesthete amputees who experience phantom limb pain, and 10 healthy controls. Results indicated that the pain synesthete group demonstrated significantly enhanced MEP response to the needle penetrating the hand, relative to the needle not having yet penetrated the hand, as compared with controls. This effect was not observed exclusively in the same muscle where noxious stimulation was applied. We speculate that our findings reflect a generalized response to pain observation arising from hyperactivity of motor mirror neurons not involved in direct one-to-one simulation but, rather, in the representation of another's experience.
AB - Observing noxious injury to another's hand is known to induce corticospinal inhibition that can be measured in the observer's corresponding muscle. Here, we investigated whether acquired pain synesthetes, individuals who experience actual pain when observing injury to another, demonstrate less corticospinal inhibition than do controls during pain observation, as a potential mechanism for the experience of vicarious pain. We recorded motor-evoked potentials (MEPs) induced at two time points through transcranial magnetic stimulation while participants observed videos of a hand at rest, a hypodermic needle penetrating the skin, a Q-tip touching the skin, and a hypodermic needle penetrating an apple. We compared MEPs in three groups: 7 amputees who experience pain synesthesia, 11 nonsynesthete amputees who experience phantom limb pain, and 10 healthy controls. Results indicated that the pain synesthete group demonstrated significantly enhanced MEP response to the needle penetrating the hand, relative to the needle not having yet penetrated the hand, as compared with controls. This effect was not observed exclusively in the same muscle where noxious stimulation was applied. We speculate that our findings reflect a generalized response to pain observation arising from hyperactivity of motor mirror neurons not involved in direct one-to-one simulation but, rather, in the representation of another's experience.
KW - Empathy for pain
KW - Phantom limb pain
KW - Synesthesia
KW - Synesthetic pain
KW - Transcranial magnetic stimulation
UR - http://www.scopus.com/inward/record.url?scp=84863611450&partnerID=8YFLogxK
U2 - 10.3758/s13415-011-0080-8
DO - 10.3758/s13415-011-0080-8
M3 - Article
SN - 1530-7026
VL - 12
SP - 406
EP - 418
JO - Cognitive, Affective and Behavioral Neuroscience
JF - Cognitive, Affective and Behavioral Neuroscience
IS - 2
ER -