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Congenital phantoms

  • It was originally claimed by Simmel (1962) that children with congenitally missing limbs do not experience phantoms,
  • but it soon became apparent that this was not always true (Weinstein et al., 1964; Poeck, 1969; La Croix et al., 1992). Weinstein et al. (1964) studied 13 congenital aplasics with phantom limbs, seven of whom were able to move the phantom voluntarily, and four of whom experienced 'telescoped' phantoms.
  • The presence of phantom arms in a patient (D.B.), a 20-year-old woman whose arms had both been missing from birth was reported by Ramachandrand (1993b). All she had on each side were the upper ends of the humerus—there were no hand bones, and no radius or ulna.
  • However, she claimed to experience very vivid phantom limbs that often gesticulated during conversation (Ramachandran, 1993b).
  • It is unlikely that these experiences are due to confabulation or wishful thinking, for two reasons.
  • First, she claimed that her arms were 'shorter' than they should be by about a foot. (She knew this because her phantom hand did not fit into the prosthesis like a hand in a glove 'the way it was supposed to.')
  • Secondly, her phantom arms did not feel as though they were swinging normally as she walked; they felt rigid.
  • These observations suggest that her phantom limbs did not originate simply from her desire to be normal. We suggest that these vivid sensations arise from the monitoring of reafference signals derived from the motor commands sent to the phantom during gesticulation.
  • What is remarkable, however, is that the neural circuitry generating these gesticulatory movements is 'hardwired' and has actually survived intact for 20 years in the absence of any direct visual or kinaesthetic reinforcement from her own limbs (although watching other people's limbs might have played a role).

[short section adapted from:

Ramachandran, VS and Hirstein, W (1998) The perception of phantom limbs. The D.O. Hebb lecture. Brain, 121, no 9., pp. 1603- 1630.

www.pdf version of this paper (If at BK or using BK dial-up software - see journal table for passwords)]

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