A view of Jerusalem's Mount Scopus .
(photo credit: MARC ISRAEL SELLEM)
Scientists at the Hebrew University of Jerusalem, in Germany and the US have found how the brain organizes its visual sense and remains intact – even in people blind from birth.
Their new study challenges conventional wisdom that blindness impairs sight-based sensory network organization.
The work was carried out by medical neurobiology Associate Prof. Amir Amedi, Dr. Ella Striem-Amit and Smadar Ovadia- Caro at Hebrew University’s Edmond and Lily Safra Center for Brain Sciences, and IMRIC, the Institute for Medical Research Israel-Canada. It has just been published in the neuroscience journal Brain.
These findings challenge the nearly half-century-long belief that the visual cortex – the area of the brain concerned with sight – fails to develop properly in people blind from birth.
“Though the ‘blind brain’ wiring may change greatly in the blind in its frontal language related parts, it still retains the most fundamental organizational principles of the visual cortex, known as retinotopic mapping (the processing of two-dimensional visual images through the eye),” Amedi said.
The scientists looked at fluctuations of activity in the visual cortex of subjects resting in an fMRI scanner. As the brain’s spontaneous activity fluctuates, different parts of the brain fluctuate together, signifying that they are part of the same functional network.
The researchers found that the same mapping divisions-of-labor present in the normally sighted brain, are also present in the brains of people born blind.
This fundamental organization of the visual cortex was even found in people whose eyes did not develop normally, suggesting normal eye development may not be necessary for the establishment of large-scale network mapping.
Previous research by neurophysiologists David Hubel and Torsten Wiesel, which earned them a Nobel Prize, suggested that sight restoration could not be attempted on people blind from birth. But Amedi insisted this is not true.
“It may be possible to successfully teach blind people to ‘see with sounds,’” he said.
Using tools of sensory substitution, it may be possible to aid people born blind in a variety of new ways. Contrary to conventional wisdom, the Hebrew University- led team suggests that many properties of visual cortex development do not require visual experience to progress and that the visual cortex does not lose all of its properties when deprived of vision.
“The brain’s map is hardwired, possibly dependent on genetically-driven processes that do not need any external sensory information for their activation,” Amedi explained.
The visual brain networks separated to up vs down, right vs left and front vs back are also present in the brains of those born blind, the Israeli researchers found.