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Brain(1998), 121,1603—1630

INVITED REVIEW


The perception of phantom limbs
The D. 0. Hebb lecture
V. S. Ramachandran and William Hirstein

Center for Brain and Cognition, 0109, University of California, San Diego, La Jolla, California, USA
1610,

Correspondence to: V S. Ramachandran, Center for Brain and Cognition, 0109, University of California, San Diego, Laiolla, CA 92093, USA. E-mail: vramacha@ucsd.edu


Summary
Almost everyone who has a limb amputated will experience a phantom limb—the vivid impression that the limb is not only still present, but in some cases, painful. There is now a wealth of empirical evidence demonstrating changes in cortical topography in primates following deafferentation or amputation, and this review will attempt to relate these in a systematic way to the clinical phenomenology of phantom limbs. With the advent of noninvasive imaging techniques such as MEG (magnetoencephalogram) and functional MRI, topographical reorganization can also be demonstrated in humans, so that it is now possible to track perceptual changes and changes in cortical topography in individual patients. We suggest, therefore, that these patients provide a valuable opportunity not only for exploring neural plasticity in the adult human brain but also for understanding the relationship between the activity of sensory neurons and conscious experience. We conclude with a theory of phantom limbs, some striking demonstrations of phantoms induced in normal subjects, and some remarks about the relevance of these phenomena to the question of how the brain constructs a 'body image.'

Keywords: phantom pain; neural plasticity; somatosensory cortex; body image; synaesthesia
Abbreviations: fMRI = functional MRI; MEG = magnetoencephalogram

Contents
Infroduction

Part I: the phenomenology of phantom limbs

Incidence
Onset
Duration
Body part
Posture of the phantom
'Telescoping'
Congenital phantoms
Factors enhancing or attenuating the phantom
Movement of the phantom
Emergence of 'repressed memories' in the phantom

Part II: experimental findings
Plasticity in the somatosensory system
Magnetoencephalogram correlates of cortical reorganization
Perceptual correlates of massive cortical reorganization
Modality-specific effects
Mechanisms of reorganization
Inter-subject variability
Non-specific responses
Extinction of referred sensations
Related studies by other groups
Inter- manual referral of tactile sensations
Phantom limb pain
Reflecting on phantom limbs
Phantoms induced in normal individuals
Phantom limbs and sensory codes
A theory of phantom limbs
The nature and nurture of phantom limbs
Concluding remarks


© Oxford University Press 1998
 

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Start | basic neuroanat. | reading | zeki extracts | table of links | List of Refs | Journals