Breaking My Brain (Temporarily) by Getting Dizzy
“The world is spinning around in a circle!”
If you spin around, you get dizzy.
That's not exactly rocket science.
We've all been there.
But you can hijack your senses like we just did and get what I'm gonna call weird dizzy.
And it can teach us how our bodies know where they are in space.
Hey smart people, Joe here.
How do you know when your body is moving?
For most of us, the answer is right here.
We can see ourselves moving.
Ok, but what if you're blindfolded?
You have a special sense that tells you whether your body is moving and how your body is oriented
in three dimensions.
It's called your vestibular sense.
And if you spin around in circles, you can break it.
But it turns out you can break your vestibular sense system in a few different ways, if you
change how you get dizzy.
We're gonna do a little experiment, to see if maybe we can decode how this vestibular
sense works.
Of course, I'm not gonna get dizzy.
I'm gonna make my friend Vanessa Hill from Braincraft do it.
Every experiment needs a control group…
Hello, hello.
Hi, it's great to be here.
Yeah, I'm kind of excited.
When you were a kid did you ever sit down in an office chair and spin yourself around as fast as you could?
Definitely
Ok, have you ever done it when you were an adult?
No.
Your sitting in an office chair, surprise.
Are you ready?
I guess so.
She's not ready
How do you feel?
Ok, everything's moving back and forth like this.
So that's normal dizzy.
Most of us have felt that.
Not too bad.
Well, watch this.
We're going to do this again, but this time we're going to hold your head in a different position
Ok
you head, you know eyeballs down 90 degrees or you can look straight up
So if I throw up it will either be back on my back or just on my lap
Probably safer to throw up down
Ok, I'm going to do that then
The world is spinning around in a circle, but it was like on an arc, everything was going up and down
What other way is there?
You're going to hold your head to the side so that your ear is facing the floor
Ready?
I suppose!
OH MY GOD
Oh that is horrible!
The whole world is just moving up and down, ok so there's a light right here
so the light was moving like this, just continually up and down
Ok, so what the heck is going on?
Your vestibular system is located in your inner ear.
It has two important parts: the semicircular canals, and the otoliths.
“Otolith” means “ear stone”.
They are literally little chunks of calcium carbonate suspended inside your head.
Basically every vertebrate has them, from fish to birds to mammals, and they're how
we sense gravity and know which way is up or down.
Otoliths also sense linear motion.
For our dizzy experiment though, we're interested in rotational motion, not linear motion.
And rotational motion is sensed by the semicircular canals.
The semicircular canals are tubes in the shape of half circles, and inside, they're filled
with fluid.
There are 3 semicircular canals in each inner ear -- three on the left and 3 on the right,
for 6 total.
Having three canals allows your body to sense motion in three dimensions, along three planes
at perpendicular angles to each other.
The superior canal detects movement along the x-axis
The lateral canal detects movement along the y-axis
And the posterior canal detects movement on the z-axis
Your inner ears are basically like the inertial guidance system in an airplane, which tells
the pilot about the plane's pitch, yaw, and roll.
How do they do that?
They use PHYSICS!
Sigh… but doesn't everything?
Specifically, they use inertia, an object's resistance to a change in its motion.
Now, when your skull moves, the liquid in your semicircular canal doesn't move immediately
with it; it sloshes around inside its tube.
The semicircular canals have special cells that sense motion called hair cells.
That inertia sloshing bends the hair cells, and bending causes a change in the signals
fired to the brain.
The hair cells are actually firing all the time, even when you're sitting still, but
bending in one direction increases the rate of firing, and bending in the other direction
decreases the rate of firing.
Each pair of canals, right and left, work together, and your brain adds up their signals
in a way that not only says “your head is moving” but tells you in which direction!
Vanessa held her head in different axes– x, y, and z–while spinning, which sloshed
the liquid in each of her three semicircular canals, one for each axis of motion, which
gave three different sensations of dizziness.
Did you notice when Vanessa said the room looked like it was spinning?
You've probably experienced that when you were dizzy too.
Well, the room wasn't spinning, I checked.
I had her hold a camera up to her eyes right as she stopped moving.
Watch what happened.
When you get dizzy, your eyes respond by jumping back and forth involuntarily.
It's called nystagmus.
If you look very closely, you'll see Vanessa's eye movements are actually faster in one direction
and slower in the other.
Normally, if you move your head with your eyes open, a reflex called the vestibulo-ocular
response moves your eyes in the opposite direction of your head's motion, in order to keep
your eyes fixated on a target.
Have you ever watched a dancer spin, and noticed how they spot on something and move their
head and eyes opposite of the spin?
It's like that.
When you stop spinning suddenly, your eye keeps twitching in the opposite direction
of spin.
It's a reflex.
The reason the room looks like it's spinning when YOU stop is because your eye movements
are MAKING it spin.
When Vanessa held her head in different positions, the room seemed to spin in different directions!
Because her vestibulo-ocular response reacted in three different ways
So how do figure skaters, pilots, or sk8r bois not get dizzy if they do so much spinning?
They do a lot of practice, and their bodies adapt.
For most sensations or feelings our bodies experience, when they're repeated and repeated,
the body's response gets weaker, it sort of tunes down the volume.
You've probably experienced this getting into cold or hot water, at first your body
REALLY senses it, but that response gets weaker as our brain tunes it down, even though you're
still feeling the cold or the heat.
It becomes your new normal.
If we consciously felt everything we're feeling all the time, it would be total sensory
overload.
And when figure skaters, pilots, or sk8r bois practice spinning over and over, their short-term
dizziness response gets weaker and weaker.
Because we evolved on Earth, these vestibular senses rely a lot on gravity.
Up in a micro-zero g environment like the Space Station, astronauts and their inner
ears are constantly falling together, all the time.
So an astronaut's vestibular system adapts to this new normal after just a few days up there
So I wanted to do a quick check today and just to see if I can make myself dizzy
it's not making me feel ill at all, not in the slightest
not dizzy
Down here on Earth, some people's vestibular systems don't work the right way, and they
can give sensations of movement or falling even when that's not happening.
That's called vertigo.
And it can make life pretty uncomfortable.
If you want to try this at home, it's super fun, you should
just make sure to do it with a friend, or to a friend, and wear a helmet
We didn't wear a helmet did we?
And you know that funny feeling in your head right now?
That's called learning.
Could be dizziness too.
Stay curious.
