20 - What Motivates You

Welcome back.

It is hard to learn

when you’re not into it.

But if it’s something you’re

really interested in,

learning is easy.

Why is that?

Most of the neurons in your cortex carry

information about what is happening

around you and what you’re doing.

Your brain also has a set of diffusely

projecting systems of neuromodulators that carry

information not about the content of

an experience but its importance

and value to your future.

Neuromodulators are chemicals that influence

how a neuron responds to other neurons,

and today we will discuss three of them;

acetylcholine, dopamine, and serotonin.

Acetylcholine neurons form

neuromodulatory connections to

the cortex that are particularly important for

focused learning when

you are paying close attention.

These acetylcholine neurons

project widely and activate

circuits that control synaptic plasticity

leading to new long term memory.

Neuromodulators also have a

profound impact on your unconscious mind.

One of the great brain discoveries

in my lifetime has been that

our motivation is controlled by a

particular chemical substance called dopamine,

which is found in a small set of neurons

in our brain stem shown here in orange.

These dopamine neurons are part of a large

brain system that controls reward learning,

and in particular, in the

basal ganglia which is located in

the green region above the dopamine neurons

and below the cortex at the top of the brain.

Dopamine is released from these neurons

when we receive an unexpected reward.

Dopamine signals project widely and

have a very powerful effect on learning,

and this is something that

also affects decision-making,

and even the value of sensory inputs.

Dopamine is in the business of predicting

future rewards and

not just the immediate reward.

This can motivate you to do something

that may not be rewarding right now,

but will lead to a

much better reward in the future.

Addictive drugs artificially

increase dopamine activity

and fool your brain into thinking that

something wonderful has just happened.

In fact, just the opposite has

just happened.

This leads to craving and dependence

which can hijack

your free will and can motivate

actions that are harmful too.

Loss of dopamine neurons leads to a lack

of motivation and something called anhedonia,

which is a loss of interest in things

that once gave you pleasure.

Severe loss of dopamine neurons

causes resting tremor,

slowness, rigidity, this is called

Parkinson’s disease.

Ultimately, it leads to catatonia,

a complete lack of any movement.

Dopamine neurons are part of the

unconscious part of

your brain that you learned about

in the first week.

When you promise to treat yourself

something after a study section,

you are tapping into your dopamine system.

Serotonin is a third diffuse

neuromodulatory system

that strongly affects your social life.

In monkey troops, the Alpha male

has the highest level of

serotonin activity, and the lowest

ranking male has the lowest levels.

Prozac, which is prescribed for

clinical depression, raises the

level of serotonin activity.

The level of serotonin is also

closely linked to risk-taking

behavior, with higher risk in

lower serotonin monkeys.

Inmates in jail for violent crimes

have some of the

lowest levels of serotonin

activity in society.

Finally, your emotions strongly

affect learning as you are well aware.

Emotions were once thought

to be separate from

cognition, but

recent research has shown that

emotions are intertwined with perception

and attention and interact with

learning and memory.

The amygdala, an almond shaped structure shown

here nestled down at the base of the brain,

is one of the major centers where cognition

and emotion are effectively integrated.

The amygdala is a part of the limbic system

which, together with hippocampus, is involved in

processing memory and decision-making

as well as regulating emotional reactions.

You will want to keep your amygdala

happy to be an effective learner.

The emotions and your neuromodulatory

systems are slower than

perception and action, but are no less

important for successful learning.

If you want to learn more about

acetylcholine, dopamine,

and serotonin, look them up on

brainfacts.org.

A website that is filled with

valuable facts about your brain.

I’m Terry Sejnowski, happy learning

until we meet again.