Think restoring sight to the blind is only a bible story?
Think again...
Hey there science fans!
Dr. Kiki from This Week in Science here for DNews.
The brain is a wild and crazy place.
For years, scientists have thought that there are periods of time during childhood, called
critical periods, when we have to have certain kinds of experience in order for our senses
to develop properly.
For our visual sense, studies suggest that the critical period for correcting any kind
of deficiency lasts from birth until about 2 years old.
After 2 years old, visual problems like amblyopia - or lazy eye - for instance, can still be
reversed, but the success rate decreases the older you get.
And, there seems to be a big difference when treatments are attempted after around age
6.
The idea of critical periods in vision was first tested by David Hubel and Torsten Wiesel
in the 1960’s by sewing kitten’s eyes shut and measuring brain activity in the visual
cortex.
Totally gruesome, I know.
Anyway, they found that the neural pathways connected to the closed eye were withered
in comparison to the normal eye, and that they never developed vision in that eye, even
after the eye was reopened months later.
Because adult cats have fully developed visual systems, sight could be restored even after
a year of having an eye sewed shut.
Hubel and Weisel won a Nobel Prize for this work.
The concept of critical periods has to do with the idea that “cells that fire together,
wire together.”
If your brain doesn’t get that early experience of visual stimulation, the neural pathways
for vision won’t have a reason to link up and create the system for vision.
In fact, it’s been shown that the visual cortex itself begins to respond to other sensory
input, like sound and touch.
You might have heard of blind people who use a form of echolocation that involves using
clicks and echoes to get around, even while riding a bike.
Brain imaging shows that the brains of these people are reorganized so that they “see”
the landscape based on what they hear.
So, knowing that the brain reorganizes in this way, with other senses taking up the
neural real estate for vision, can that process be reversed or is it really permanent?
An exciting study published in the Journal of Neurophysiology this week by a research
team from the Universite de Montreal and the University of Trento suggests that it can…
kind of.
The team imaged the brain of a 50-year-old woman both before and after she underwent
surgery to implant an artificial cornea, called a Boston Keratoprosthesis, in her right eye.
The woman had extremely low levels of vision her entire life, and compared to people with
normal sight and those who lost their sight later in life, she had both structural and
functional reorganization of the visual cortex.
Before the surgery, the visual area responded to auditory input.
However, after the surgery, there was a significant reduction in the auditory response, but it
wasn’t total, even after 7 months.
So, this study and others along these lines suggest that some of the brain shaping that
takes place during the critical periods of development is permanent, but some of it can
be reversed.
The trick now will be discovering what makes the difference.
Do you want to help sight restoration research happen?
You can!
By donating to Fight For Sight, an organization that supports and inspires research in vision
and related sciences by granting funds to scientists early in their careers.
What do you think of research like this?
Does it give you hope?
Tell us in the comments below or you can find me on Twitter at Dr. Kiki.
And be sure to subscribe to DNews for more science every day.