Narrator: Saturday, 12 p.m., the light burns,
your head throbs, and you have no recollection
of how you got back home.
Don't worry, you're not alone.
More than half of college students experience blackouts,
according to several studies.
And let's be clear, blacking out doesn't mean passing out.
You were probably awake and aware the entire night.
So then, where did all those memories go?
Let's rewind to Friday night.
Normally, whenever you have an experience,
like a conversation, a part of your brain
called the prefrontal cortex stores that information
in short-term memory.
Then, another part of your brain called the hippocampus
weaves those experiences together,
so they can be stored away as long-term memories.
So the next day, you remember the party as a whole,
instead of smell of sweat, house music, Jen was there.
But here's the key part.
Storing these episodes in long-term memory
requires special neurotransmitters.
But your liquor shots prevent the neurotransmitters
from working properly.
So instead of remembering the party,
all you have is an incomplete, or even empty file.
And the amount of alcohol in your system at the time
influences how much you remember.
Let's say you're a 73 kilogram adult man,
and you've done eight shots in one hour.
Your blood alcohol content is probably
around .2% by this point,
more than twice the legal limit for driving a car.
And your brain may still be able to store some memories,
so you end up with islands of memories
separated by missing sections.
That's called a fragmentary blackout,
aka a grayout or brownout.
But if you keep pounding those shots, it gets worse.
Within the next half hour,
you pound back another four shots.
Now your blood alcohol content hits around .3%,
and your hippocampus goes dark, and full amnesia sets in.
This is called an en bloc blackout,
and once you wake up, that entire night could be blank.
Push your BAC much higher than that, and you might die.
And yet your friends might not even realize
you're in the middle of a blackout,
since the alcohol didn't delete your long-term memories
already safe in storage before the night began.
So you can still carry on conversations
and behave more or less like a typical person, to an extent.
Blackouts aside, alcohol can still interfere
with other regions of your brain,
including those responsible
for reasoning and decision-making.
So during blackouts, people have crashed cars,
gotten into fights, and committed
or been the victims of sexual assault.
They might just not remember it.
That being said, not everyone gets blackouts.
Your sex, body weight and family history all play a role.
So that could explain
why your friends recall the entire night,
despite downing just as much tequila.
But it won't save them
from a wicked hangover the next morning.