Sight from sound

Sight from sound

Brain scientists tap into the visual cortex of people suffering from congenital blindness, making it possible for them to “see” using a video camera connector to a smartphone

Scientists at the Hebrew University of Jerusalem have tapped onto the visual cortex of the congenitally blind by using sensory substitution devices (SSDs), enabling the blind in effect to “see” and even describe objects.
SSDs are non-invasive sensory aids that provide visual information to the blind via their existing senses. For example, using a visual-to-auditory SSD in a clinical or everyday setting, users wear a miniature video camera connected to a small computer (or smart phone) and stereo headphones.
The images are converted into “soundscapes,” using a predictable algorithm, allowing the user to listen to and then interpret the visual information coming from the camera.
Remarkably, proficient users who have had a dedicated (but brief) training as part of a research protocol in the lab of Amir Amedi at the Hebrew University, are able to use SSDs to identify complex everyday objects, locate people and their postures, and read letters and words.
In addition to SSDs’ clinical opportunities, using functional magnetic resonance imaging opens a unique window for studying the organisation of the visual cortex without visual experience by studying the brain of congenitally blind individuals.
The results of the study were recently published in the journal Cerebral Cortex, are surprising. Not only can the sounds, which represent vision, activate the visual cortex of people who have never seen before, but they do so in a way organised according to the large-scale organisation and segregation of the two visual processing streams.
Using sensory substitution, the Hebrew University scientists, led by Ella Striem-Amit and Amedi, discovered that the visual cortex of the blind shows a similar visual pathway division-of-labour when perceiving sounds that convey the relevant visual information; when the blind are requested to identify either the location or the shape of an SSD “image,” they activate an area in the dorsal or in the ventral streams, respectively.
“The brain is not a sensory machine, although it often looks like one; it is a task machine,” summed up Amedi.
These findings suggest that the blind brain can potentially be “awakened” to processing visual properties and tasks, even after lifelong blindness, with the aid of visual rehabilitation, using future medical advances, such as retinal prostheses, say the researchers.

(MM19Feb12)