How does alcohol cause blackouts? - Shannon Odell
In 1969, Dr. Donald Goodwin gathered
a group of study participants
and asked them each to recall the object
he'd shown them two minutes prior.
The twist?
All the participants
were very intoxicated.
Despite this, most could pay attention
to the task
and correctly name the toy
they had just seen.
Yet, when Donald asked them to recall
that object a mere 30 minutes later,
half the participants drew a blank,
having “blacked out” the earlier
moment entirely.
This study illustrates the strange
and somewhat selective effects
alcohol has on the brain.
Many intoxicated people can perform
complex tasks
like holding a detailed conversation
or navigating a walk home.
Yet for those experiencing what
is known as a blackout,
the memory of these events
is quickly forgotten.
So how does alcohol cause
these memory lapses?
First, let's identify the culprit.
While a single drink often contains
hundreds of different chemical compounds,
ethanol is responsible for alcohol's
effects on the brain.
Ethanol is lightweight and lipophilic,
meaning its structure easily dissolves
into fats,
like those in the membranes
of the outer blood-brain barrier.
Once inside the brain,
ethanol’s unique structure
allows it to bind to, interact, and affect
many different neuronal receptors,
impairing pathways that allow you to make
careful decisions, control your impulses,
and even manage your motor skills.
And the networks that control memory
seem to be especially sensitive
to alcohol’s effects.
Typically, information about your
surroundings is taken in
by your sensory organs
and sent to the brain.
Neurons transfer this information
to one another
via chemical messengers
called neurotransmitters,
which are released by one neuron
and received by receptors at another.
When a neurotransmitter
binds to a receptor,
it unlocks an internal channel,
allowing small ions to flow into the cell.
If enough ions enter the cell,
the neuron fires,
sending the signal forward.
Through this process,
different regions of the brain
can communicate with one another
in milliseconds,
creating our moment-to-moment
understanding of the world.
But ethanol interacts with receptors,
making it harder for neurons
to communicate.
While compromised, the brain is
still able to transfer information,
which is why many intoxicated people
seem somewhat capable
of performing basic tasks.
In other words, brain function
is highly impaired,
but not completely broken.
But memory storage is a different story.
The transfer of
moment-to-moment understanding
to something we can remember
is thought to depend on a process
called long-term potentiation, or LTP.
LTP happens throughout the brain,
but is especially important
in learning and memory regions,
like the neocortex and the hippocampus.
During LTP,
the firing of a neuron triggers
physical changes to its structure.
For example, more receptors may be
moved to the cell's surface,
making the neuron more sensitive
to future signaling from its neighbors.
These physical changes increase
the likelihood that a cell
will fire again at that connection,
strengthening the wiring between neurons.
And through this stronger connection,
it's thought that a stable
memory is formed.
Yet studies suggest that ethanol has
a unique ability to disrupt LTP,
blocking the physical changes
needed for memory formation.
So, while moment-to-moment information
is encoded and understood,
the storage of that information
is blunted,
resulting in a blackout.
Of course, not all levels of drinking
result in blackouts.
They happen when the concentration
of alcohol in the blood, or BAC,
exceeds a certain level,
approximately 0.16.
But there’s no magic number.
At slightly lower BACs, brownouts,
or the spotty memory of events, can occur,
as some neurons continue to function
properly while others fail.
And drinking too much can cause
a person to pass out altogether.
Other factors like dehydration level,
genetic differences, medications,
and even how much you’ve eaten
can affect the likelihood of a blackout.
And teenagers appear to be
especially vulnerable
due to the substantial changes
in brain development during those years.
Alcohol’s short-term effects
usually don’t last longer
than the time it takes for their body
to metabolize it, or about a day.
But repeatedly over-drinking can damage
neurons and permanently impair memory.
It can also harm other organs
like the liver,
which works overtime
breaking down alcohol.
After all, experiencing a blackout
or witnessing others
in this compromised state
can be a lot for your mind
and body to process.
