Cohen et al. (1997)

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Revision as of 15:36, 28 April 2008

The Title of the article was Functional Relevance of Cross-Modal Plasticity in Blind Human

Hypothesis

The motivation behind this article was if there is a connection between the process of somatosensory information and the visual cortex in blind individuals. "It is unknown whether the visual cortex can process somatosensory information in a functionally relevant way." The hypothesis was that the visual cortex will be recruited by your somatic senses (touch) when doing discrimination tasks, such as Braille.

Method

There were four groups of subjects, early blind people using Braille, early blind people testes using embossed letters, volunteers with 20/40 acuity using embossed letters, and a last group similar to the early blind group but with a higher magnetic stimulus.

Subjects were prompted to read different letter combinations. In the embossed group, there were 8 strings of 3 embossed letters, and in the Braille group, there were 5 strings of 5 Braille letters. Their fingers pass over the laser beam and their brains are stimulated. The laser's purpose is to induce Transcranial Magnetic Stimulation. TMS is accomplished by a placing a figure-eight water-cooled coil on the scalp, which sends a small magnetic current to the brain and disrupts the magnetic field. This tests to see if there is a temporary change in reading letters. When the current fires, a loud clicking noise occurs. Stimulization was randomized among brain areas.

File:Http://www.nature.com/nature/journal/v389/n6647/images/389180aa.tif.2.gif

Results

Both blind subject groups induced the most error when the mid-occipital cortex was stimulated. The subjects described somatosensory perceptions that were distorted, like there were missing dots or more dots in the Braille. For sighted patients, the error occurred most in the S-M contra (Contralateral primary Sensorimotor Region). There were hand-jerking movements, but this did not lead to distorted somatosensory perceptions.

Conclusions

The conclusion was that blindness from an early age can cause the visual cortex to be recruited in somatosensory processing.