Feeling vibrations: enhanced tactile sensitivity in congenitally deaf humans

The human nervous system displays remarkable functional plasticity followin g long-term sensory deprivation. For example, the auditory cortex of congen itally deaf humans may start to process tactile information. To further exp lore this type of cross-modal plasticity, we examined the tactile accuracy of congenitally deaf and normal hearing subjects in frequency discriminatio n and in detection of random suprathreshold frequency changes within a mono tonous sequence of vibratory stimuli. We found that congenital deafness can enhance the accuracy of suprathreshold tactile change detection while tact ile frequency discrimination is not significantly changed, although there i s a trend toward reduced thresholds. The enhanced tactile sensitivity in th e deaf probably reflects both neural plasticity and increased attention dir ected to the stimuli. Whatever the underlying neural mechanisms might be, f unctional compensation following early sensory loss apparently leads the re maining sensory modalities to develop capacities exceeding those of the nor mal functional systems. (C) 2001 Elsevier Science Ireland Ltd. All rights r eserved.