Practice makes perfect: the neural substrates of tactile discrimination by Mah-Jong experts include the primary visual cortex

When participants performed tactile discrimination of Mah-Jong tiles, the left lateral occipital cortex (LO) and V1 were activated in the well-trained subjects. In the na？ve subjects, the LO was activated but V1 was not activated. Both the LO and V1 of the well-trained subjects were activated during Braille tactile discrimination tasks.The activation of V1 in subjects trained in tactile discrimination may represent altered cross-modal responses as a result of long-term training.Visual-tactile cross-modal plasticity due to visual deprivation has been reported [1-5]. For visually-deprived persons, Braille is the most successful system for the transmission of written information. In Braille, the visual perception of printed characters is replaced by the tactile interpretation of raised dots. Braille reading is known to activate the visual cortex of the blind, indicating remarkable cortical plasticity. However, such findings typically come from experiments in subjects who have been blind from a very early age and who also have undergone Braille training from a young age. As a result, it is not clear whether the visual cortex activation is related to long-term Braille training or to visual deafferentation. A previous study has shown that non-Braille haptic processes activate the visual cortex of blind subjects who read Braille proficiently, which is consistent with the latter hypothesis [4]. Additionally, the occipital cortex of blind subjects without Braille training was activated during tactile discrimination tasks, whereas that of control sighted subjects was not [4]. Hence the activation of the association visual cortex of blind subjects while performing a tactile discrimination task may be due to sensory deafferentation, wherein a competitive imbalance favors the tactile over the visual modality. Recent studies indicate that both tactile and visual processing of objects are represented in the visual association cortex [6,7], indicating that visual and tactile proces