Ptito et al. (2005)

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Cross-Modal Plasticity Revealed by Electrotactile Stimulation of the Tongue in the Congenitally Blind (Ptito et al., 2005)

The experimenters in this study used PET to study cross-modal plasticity in the congenitally blind, using electrotactile stimulation of the tongue.

Participants

Participants included 6 blind and 5 sighted blind-folded controls.

Training

Participants were trained to use their tongue in a Snellen orientation detection task. They were scanned before and after training.

Results

Before training, no significant changes in regional cerebral blood flow (rCBF) was observed in the occipital cortex of either group. After practice for the blind, however, activity in the occipital cortex increased. This increase in activity was not observed in the sighted participants yet there was an increase in somatosensory activity, providing evidence for training-induced plasticity in the congenitally blind.

An inter-regional correlation analysis showed that task-related rCBF changes in the left posterior parietal cortex were positively correlated with rCBF changes in the occipital area of the trained blind participants.

Conclusion

This data revealed that cross-modal plasticity in the blind develops rapidly and that the occipital cortex is part of a functional neural network for tactile discrimination in conjunction with the posterior parietal cortex. Data further showed that the tongue can act as a portal to convey somatosensory information to visual cortex and that with no visual input the occipital lobe assumes the role of tactile discrimination. This modification of the brain is an example of plasticity.