Washington: A person's senses of touch and hearing become sharper when vision is lost but exactly how this happens has been unclear.

Now a long-term study by Berenson-Allen Center for Noninvasive Brain Stimulation at Beth Israel Deaconess Medical Center (BIDMC) demonstrates that sudden and complete loss of vision leads to profound - but rapidly reversible - changes in the visual cortex.

These findings not only provide new insights into how the brain compensates the loss of sight, but also suggest that the organ is more adaptable than originally thought.

"The brain's ability to reorganise itself is much greater than previously believed," explained co-author Alvaro Pascual-Leone, professor of Neurology at Harvard Medical School (HMS).

"In our studies [in which a group of sighted study subjects were blindfolded for five days], we have shown that even in an adult, the normally developed visual system quickly becomes engaged to process touch in response to complete loss of sight."

Or, as another co-author Lotfi Merabet, described: "In a sense, by masking the eyes, we unmask the brain's compensatory potential."

The scientists had previously shown that subjects with normal vision who are blindfolded for a five-day period performed better than non-blindfolded control subjects on Braille tests.

Subsequent brain scans found that blindfolded subjects also experienced dramatic changes in the brain's visual cortex.

"We recruited 47 subjects to participate in the study," explained Merabet, assistant professor of Ophthalmology and Neurology at HMS. "Half of the study participants remained completely blindfolded, 24 hours a day, for a total of five days under the careful watch of the staff of BIDMC's General Clinical Research Center.

The other half were only blindfolded for testing, but spent the rest of the day seeing normally. During their stays, both sets of study participants underwent intensive Braille instruction for four to six hours a day from a professional instructor from the Carroll Center for the Blind."

The study participants also underwent serial brain scans (known as fMRI or functional magnetic resonance imaging) at both the beginning and end of the five-day study period.

As predicted, the researchers found that the subjects who were blindfolded were superior at learning Braille than their non-blindfolded counterparts.

These findings were reported in the Wednesday issue of the journal PLOS One. IANS