Perceptual distortions of the human body image produced by local anaesthesia, pain and cutaneous stimulation
Article first published online: 8 SEP 2004
The Journal of Physiology
Volume 514, Issue 2, pages 609–616, January 1999
How to Cite
Gandevia, S. C. and Phegan, C. M. L. (1999), Perceptual distortions of the human body image produced by local anaesthesia, pain and cutaneous stimulation. The Journal of Physiology, 514: 609–616. doi: 10.1111/j.1469-7793.1999.609ae.x
- Issue published online: 8 SEP 2004
- Article first published online: 8 SEP 2004
- (Received 19 August 1998; accepted after revision 12 October 1998)
- 1Knowledge of the size and orientation of the hand is essential if it is to be moved accurately in space. We used two psychophysical methods to determine whether the perceived size of a body part changes when its sensory input is changed: first, the selection of scaled drawings which matched the apparent size of a body part, and second, a motor task in which the subject drew the body part to depict its perceived size.
- 2Complete anaesthesia of the thumb (with a digital nerve block) significantly increased its perceived size by 60–70% when assessed with both psychophysical methods. During this anaesthesia, the perceived size of the adjacent index finger or digits on the contralateral side was unaltered. However, the size of the unanaesthetized lips increased (by ∼50%).
- 3Marked sensory loss for the lips (produced by topical anaesthetics) significantly increased their perceived size when assessed with both methods of measurement. There was a small increase in apparent size of the thumb.
- 4To determine whether changes in perceived size could also be produced by an elevation of peripheral inputs, innocuous electrical stimulation of the digital nerves and also painful cooling of the digit were used. Both procedures produced small but significant increases in perceived size of the stimulated part.
- 5The results highlight lability in the perceived size of parts of the body and how this affects motor output. The data may reveal perceptual consequences of acute changes in central somatosensory maps, changes which are known to occur with deafferentation.