Reduced EEG alpha activity over parieto-occipital brain areas in congenitally blind adults.

OBJECTIVE

Goal of the present study was to compare the amplitude and topography of EEG alpha activity between congenitally blind and sighted adults both in a primarily sensory and a primarily cognitive task.

METHODS

Congenitally blind and blindfolded sighted adults performed a somatosensory perception task (experiment 1), which required to discriminate tactile stimuli at different fingers, and a mental imagery task (experiment 2), in which a previously haptically encoded map had to be mentally scanned. The EEG was recorded with 61 electrodes and was analyzed with the Fast Fourier Transformation (FFT).

RESULTS

Results showed a significant reduction of alpha power in the blind compared to the sighted controls over parieto-occipital recording sites in both tasks.

CONCLUSIONS

It is speculated that brain structures, which have been associated with the generation of posterior alpha rhythms in sighted adults, including the geniculo-cortical pathway, depend on visual input and might either be reorganized or atrophied following blindness from birth.

SIGNIFICANCE

The present study demonstrates that oscillatory activity of the brain might serve as a marker of cortical reorganization.