358 the auditory cortex appear to be the same as those of visual cortical plasticity.^10
Compensatory improvement of auditory abilities in the blind had long been postulated,
claiming, among other things, improved musical abilities (Figure 23.1).
While it is often difficult to quantitatively assess musical abilities, other auditory
perceptual capacities can be tested more easily. An ability of blind people to localize sounds
with greater precision has been found in a number of recent studies.11,12These studies
followed on the footsteps of work in visually deprived cats^13 and ferrets^14 that had also
demonstrated improved sound localization abilities in these animals. Animal studies can
additionally be used to find the neural bases of these behavioural improvements. In blind
cats, visually deprived by binocular lid suture from birth, an area in the parietal cortex
(the anterior ectosylvian visual area [AEV]) that is normally innervated by visual fibres
originating in extrastriate cortex and visual pulvinar^15 is completely taken over by auditory
and somatosensory inputs.^16 At the single unit level, auditory cortical neurons show greater
selectivity for the position of sounds in space.^17 Taken together, these findings suggest a
greater sampling density of auditory space in the cerebral cortex as the basis for the greater
precision in sound localization of blind individuals.^9 Furthermore, the expansion of audit-
ory territory in the cerebral cortex would appear to enable other refinements of auditory
perception as well.
Modern neuroimaging techniques, such as positron emission tomography (PET), can be
used to look for such crossmodal map changes directly in blind humans. During localizationFigure 23.1Anecdotal evidence reports superior musical abilities in blind individuals.Left: Stevie Wonder. From:
The Rolling Stone. Illustrated History of Rock and Roll. A. DeCurtis, J. Henke, H. George-Warren (eds) New York:
Random House, p. 294.Right: Wolfgang Amadeus Mozart, though not blind, possibly suffered from strabismic
amblyopta, reducing vision in one or both eyes by an unknown amount. Portrait attributed to Kymli of
Mannheim, Germany, 1783 (held in a private collection). (See Plate 17 in colour section.)Zat-Ch23.qxd 6/21/03 10:13 AM Page 358