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Phantom digit somatotopy: a functional magnetic resonance imaging study in forearm amputees
Author(s) -
Björkman Anders,
Weibull Andreas,
Olsrud Johan,
Henrik Ehrsson H.,
Rosén Birgitta,
BjörkmanBurtscher Isabella M.
Publication year - 2012
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2012.08099.x
Subject(s) - somatosensory system , phantom limb , functional magnetic resonance imaging , secondary somatosensory cortex , cortex (anatomy) , neuroscience , premotor cortex , forearm , stimulation , posterior parietal cortex , amputation , sensory cortex , anatomy , sensory stimulation therapy , magnetic resonance imaging , somatosensory evoked potential , imaging phantom , psychology , medicine , dorsum , nuclear medicine , surgery , radiology
Forearm amputees often experience non‐painful sensations in their phantom when the amputation stump is touched. Cutaneous stimulation of specific stump areas may be perceived as stimulation of specific phantom fingers (stump hand map). The neuronal basis of referred phantom limb sensations is unknown. We used functional magnetic resonance imaging to demonstrate a somatotopic map of the phantom fingers in the hand region of the primary somatosensory cortex after tactile stump stimulation. The location and extent of phantom finger activation in the primary somatosensory cortex corresponded well to the location of normal fingers in a reference population. Stimulation of the stump hand map resulted in an increased bilateral activation of the primary somatosensory cortex compared with stimulation of forearm regions outside the stump hand map. Increased activation was also seen in contralateral posterior parietal cortex and premotor cortex. Ipsilateral primary somatosensory cortex activation might represent a compensatory mechanism and activation of the non‐primary fronto‐parietal areas might correspond to awareness of the phantom limb, which is enhanced when experiencing the referred sensations. It is concluded that phantom sensation elicited by stimulation of stump hand map areas is associated with activation of finger‐specific somatotopical representations in the primary somatosensory cortex. This suggests that the primary somatosensory cortex could be a neural substrate of non‐painful phantom sensations. The stump hand map phenomenon might be useful in the development of prosthetic hand devices.