Holmes NP (1999) The self in its brain: Neural representations of the body. BSc Thesis, University of Manchester, 34pp.
The psychological construct of the body schema (or body image), was invoked to explain some curious clinical ‘disturbances’ following central nervous system lesions. Only when Penfield began electrical exploration of the cerebral cortex in the late 1920’s, did neurophysiological evidence pertaining to the representation of the body in the brain become available. This paper puts forward two lines of evidence in support of a model for neural body representations. Firstly, the clinical phenomena and neural correlates of phantom limbs are reviewed. Melzack’s neuromatrix hypothesis, and the reorganisation hypothesis of Ramachandran and co-workers are then discussed in some detail. Secondly, the effects of empirical sensory manipulations in primates and man demonstrate significant plasticity in both neural and perceptual domains. Evidence of somato-cortical reorganisation following selective deafferentation is reviewed, and two hypotheses for reorganisation mechanisms (unmasking of latent connectivity and axonal sprouting) are discussed. Finally, muscle vibration-induced perceptions of anatomically impossible body configurations are examined. Six aspects of the representation of the body are highlighted. The representations are multi-modal, distributed, constrained, dynamic, use-dependent, and co-incident. A speculative model of sensory integration, depending on direct connections between corresponding positions in abstract topographic or computational maps is used to account for some of the findings of the reviewed research. The function of the representation of the body in the brain is seen as that of piloting the organism through the environment, attending only to salient details in order to produce a ‘best fit’ working body schema