ABSTRACT
Representational plasticity, that is, expansion and reorganization of cortical maps, has been demonstrated most convincingly in the somatosensory cortex (Kaas, 1991; Kaas, Merzenich, & Killackey, 1983; Merzenich, Recanzone, Jenkins, Allard, & Nudo, 1988) and, more recently, also within the auditory cortex (Recanzone, Schreiner, & Merzenich, 1993). Mostly, such changes have been obtained as the result of enhanced experience within the same modality. By contrast, the majority of the studies summarized in this chapter describe an expansion of maps in one modality as a result of deprivation in another. In discussing the common theme of this book, a generalized theory of neuroplasticity, the question naturally arises what intermodal (or cross-modal) plasticity has in common with intramodal plasticity. At the single-neuron level, changes in tuning properties are observed in both intra- and intermodal plasticity (Rauschecker, 1991, 1995). Sharper tuning is thought to correspond to better resolution and thus better performance of the neural system. Better performance of the neural system is assumed to lead to better behavioral performance as well. Representational plasticity or expansion of maps seems to have the same effect: an increase in the number of elements participating in the encoding of the sensory world is thought to lead to better perceptual performance within the sensory modality corresponding to the expanded map regardless of the modality that causes the expansion.
