This study will examine whether tactile (touch) abilities at the lip are more acute in
people with upper limb amputation compared with healthy normal volunteers. People with an
amputated upper limb have an expanded brain representation of the lip that may correlate
with heightened tactile spatial acuity.
Normal volunteers will be recruited for this study. Candidates will be screened with
physical and neurological examinations. (Amputee volunteers will be studied at the amputee
clinic at the University of Tubingen, Germany.)
Participants will sit comfortably in a chair, wearing a blindfold, during the following
- Plastic domes with grooves are placed on parts of the lower lip on either side for a
few seconds. The volunteer is then asked to identify the direction of the grooves
relative to the long axis of the lip.
- The participant's arm is placed in a cast and the index finger is immobilized. The same
test done on the lip is repeated on the distal part of the index finger.
Each part of the test lasts about 20 minutes, and the entire experiment takes about 2 hours.
Upper limb amputation leads to expansion of the cortical representation of the lip into the
adjacent deafferented hand representation. It is conceivable that this enlargement of the
lip representation may translate into a behavioral gain. The purpose of this protocol is to
test the hypothesis that upper limb amputation in humans results in higher tactile spatial
acuity at the lip. This would represent the first demonstration of chronic
deafferentation-induced behavioral gains within the somatosensory system.
Normal volunteers who are willing and able to stay relaxed and collaborative for a period
of up to 2 hours.
Subjects with upper limb amputation more than one year before testing.
Neurological or psychiatric disease
Excessive callus at the palm of the fingers
Subjects, who are unable to perform or understand the task