How the brain adapts to hear better after vision loss

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By Maria Cohut 

Fact checked by Paula Field

Both scientific studies and
anecdotal evidence have suggested that people who experience vision loss often
develop a more enhanced sense of hearing. So what happens inside the brain? New
research investigates.
According to the World Health
Organization (WHO), around 1.3 billion people worldwide have a form of vision
impairment, which ranges from mild eyesight problems to legal blindness.
The Centers for Disease
Control and Prevention (CDC) note that over 3.4 million people aged 40 and
above in the United States are either legally blind or live with a form of
visual impairment.
Anecdotal information has
suggested that people who lose all or much of their eyesight have stronger
senses of touch and hearing than people with 20/20 vision. This is because they
have to rely so much more on their other senses to navigate the world.
Indeed, researchers have shown
that people with severe visual impairments can perform better than
fully-sighted people on hearing tasks and are better able to locate the source
of a sound. Other research also reveals that people who lost their eyesight
early in their life can hear sounds better than people without vision loss.
Previous studies have
suggested that the brains of people with vision loss can adapt and
“rewire” to enhance their other fully functional senses.
Now, research conducted by a
team from the University of Washington in Seattle and the University of Oxford
in the United Kingdom has discovered what changes take place in the brains of
people who lost their eyesight at an early age that makes them better able to
process sound.
The new study — whose findings
appear in The Journal of Neuroscience — looks at what happens in the auditory
cortex brain region of people who lost their sight at an early age.
What happens in the auditory

Existing studies have shown
that when people have early vision impairment, the occipital cortex — usually
tasked with “deciphering” visual input from the eyes — adapts to
process information from other parts of the body.
However, as study author Kelly
Chang and colleagues observe, it seems that the auditory cortex also adapts to
process sound differently and “make up” for the loss of sight.
In the new research, Chang and
team studied these changes in people with early blindness — including some with
anophthalmia, a condition in which both eyes do not develop sight — comparing
them with a control group of fully sighted individuals.
The investigators conducted
functional MRI scans of the participants’ brains as they processed pure tones —
tones that sound the same at different frequencies — and analyzed what happened
in their auditory cortexes.
The scans revealed that,
although both participants with early blindness and fully sighted participants
had auditory cortexes of similar sizes, this brain region was better able to
capture specific finely tuned frequencies in those with vision loss.
These findings, the
researchers note, add to our understanding of how people with early blindness
adapt to the loss of sight, and why they can sometimes have a more enhanced
sense of hearing, compared with others.
In the future, Chang and
colleagues aim to study what happens in the brains of people who lost their
vision later in life, and in those of individuals who were able to recover
their eyesight.
The researchers hope that
pursuing this path of investigation will allow them to better understand the
underlying mechanisms through which the brain adapts to changes in the five

Kayode Ojo
Kayode Emmanuel Ojo is the Co-Founder and Managing Director at SHEFFA Limited. He is presently studying Computer Science at the National Open University, Victoria Island, Lagos.