(photo credit: Courtesy/MCT)
Can the blind “see” with their ears? Hebrew University of Jerusalem brain
scientists have tapped onto the visual cortex of people suffering from
congenital blindness by using sensory substitution devices (SSDs) – making it
possible for them in effect to “see” and even describe objects.
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 smartphone) 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
Surprisingly, proficient users who have had special training in a
short time as part of a research protocol in the lab of Dr. Amir Amedi are able
to use SSDs to identify complex everyday objects, locate people and their
postures and read letters and words.
Amedi is a scientist at HU’s Edmond
and Lily Safra Center for Brain Sciences and the Institute for Medical Research
In addition to SSDs’ clinical opportunities, using
functional magnetic resonance imaging opens a window for studying the
organization of the visual cortex without visual experience by studying the
brain of the congenitally blind, he said.
Amedi and his lab team
published in the journal Cerebral Cortex
that not only can the sounds – which
represent vision – activate the visual cortex of those who have never seen
before, but they do so in a way organized according to the large-scale
organization and segregation of the two visual processing streams.
the past 30 years, it has been known that visual processing is carried out in
two parallel pathways – the ventral occipito-temporal “what” pathway (“ventral
stream”) has been linked with visual processing of form, object identity and
Its counterpart is considered to be the dorsal occipitoparietal
“where/how” pathway, (the “dorsal stream”), which analyzes visuo-spatial
information about object location and participates in visuo-motor
Using sensory substitution, the HU scientists, led by doctoral
student Ella Striem- Amit, and Amedi, discovered the visual cortex of the blind
shows a similar dorsal/ventral visual pathway division-of-labor when perceiving
sounds that convey the relevant visual information. When the blind are asked 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.
that the most important large-scale organization of the visual system into the
two streams can develop at least to some extent even without any visual
experience, suggesting instead that this division-of-labor is not at all visual
in its nature. “The brain is not a sensory machine, although it often looks like
one; it is a task machine,” Amedi stressed.
The researchers believe that
the blind brain can potentially be “awakened” to processing visual properties
and tasks, even after lifelong blindness, with the help of visual
rehabilitation, using future medical advances, such as retinal prostheses, say
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