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You might think of your eyes like cameras
that just take in light from the world around you
to recreate a perfect snapshot in your
brain.
But in reality, your brain does a lot of processing
before you even perceive an image.
And now, scientists have found a way to hack
that process and generate shapes directly on the brain
so that a person can see them without using
their eyes.
The trick they used to do this reveals how
vision is laid out in the brain,
and could even offer a way for people who
have lost their sight to process visual signals
without their eyes.
For those who can see, the process begins
when light hits the eyes.
There, light-sensitive cells send electrical
signals down the optic nerve,
where they eventually reach a region in the
back of your brain called the visual cortex.
At this point, you’re still not consciously
aware of what you’ve seen.
Your visual cortex processes the raw visual
information it gets from your eyes first,
before you become conscious of it.
And this region plays a pretty important role
in how you see the world.
Like, it can produce optical illusions even
if your eyes take in signals perfectly.
But even weirder, if you stimulate the visual
cortex,
it can make you see things even if your eyes aren’t involved at all.
And that’s the idea that vision researchers
find so intriguing.
Scientists began testing this out in the 1950s,
but one of the most important studies was done by researchers at the University of London in the 1960s.
They surgically implanted an array of electrodes onto the brains of two participants who had lost their sight.
The electrodes were specially designed to
deliver small electrical currents
to different regions  of the visual cortex,
 activating the brain cells there.
Each time a single electrode was switched on,
the participants reported seeing 
a very small spot of white light.
And when electrodes were activated in different
parts of the cortex one at a time,
that little spot of light showed up in different
parts of their field of view.
Based on where the subjects saw the spot of
light,
the scientists were able to connect certain regions of the brain with specific parts of the visual field.
In fact, they found that a part of the visual
cortex called V1
is basically an exact projection of your visual
field onto the physical structure of your brain.
And, incredibly, their results essentially
confirmed maps of human vision
that doctors had drawn up based on soldiers’
injuries back in World War I.
Because the visual cortex is so neatly arranged,
researchers eventually became interested 
in seeing how precisely
they could place images in someone’s visual
field just by stimulating the brain.
Scientists thought that if they could stimulate
V1 to make those spots of light,
now known as phosphenes, 
show up wherever they wanted,
maybe they could combine them to make shapes,
like letters of the alphabet.
Scientists hypothesized that it would work
just like how individual pixels on a computer monitor
come together to display text.
Unfortunately, over the next few decades,
no one found much support for that idea.
Then, in a study published in May of 2020 in the journal Cell, researchers finally had a breakthrough.
But at first, they ran into problems, too.
They found that stimulating multiple regions
of V1 at the same time with an array of electrodes
didn’t produce an image of multiple phosphenes.
Instead, participants typically reported seeing
one bigger blob of light.
And that gave them a clue.
They speculated that the currents being applied
to each region weren’t staying isolated,
and they were combining to activate more regions
of V1 than they were meant to.
So the team decided to try something different.
Instead of trying to create a whole shape
at once, they would use electrodes to trace
the outline of shapes on the brain.
This would avoid the problem of having multiple
electrodes active at once
and prevent their signals from blending together.
It took a little creativity, the researchers had to find a way to trace a continuous path on the brain,
and they only had 24 electrodes, so they couldn’t
connect the dots very smoothly.
But by manipulating electric currents, they
were able to guide the phosphene down a smooth path
and trace out letters on the brain.
And amazingly, it worked!
Participants who had lost their sight not
only recognized these letters,
they could even trace out similar versions
of them with their fingers.
One participant was even able to recognize
a sequence of letters
at a rate of about 1 every 2 seconds with 92% accuracy.
This was incredibly exciting for the researchers,
because ever since the 1960s, when scientists first started studying phosphenes,
their primary motivation was to create a kind of prosthetic for people who had lost function in their eyes.
And having a way of tracing recognizable shapes
directly onto the visual cortex
opens up a lot of possibilities.
For example, by having cameras study the environment,
modern computer vision algorithms
could draw cues on the visual cortex
that people who have lost their sight could
potentially use to navigate the world.
Even though that’s a long way off, figuring
out how to write on the brain is a huge first step.
While scientists work on creating shapes on
the brain,
maybe you’re interested in creating 
visual experiences of your own,
like videos or animations, and Skillshare
can help with that.
Skillshare is an online learning community
where you can learn creative skills,
ranging from production skills to art.
Like, if you’re interested in creating your own videos, they have a course on Filmmaking from Home
that teaches you how to take scenes from your
life and turn them into a compelling video.
The classes are short, so you can squeeze
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Skillshare is also super-affordable, you can
get a Premium Membership
with unlimited access to classes and communities for less than $10 a month.
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[♪ OUTRO]
