What is learning?
Take a few moments and produce your own
definition of what learning is.
What kinds of things do you learn?
How do you learn them?
Different Domains of Learning
Facts and information
Procedures (how to solve a
Physical patterns of activity
Learning to “feel” something
Write your own example of:
What do these types of learning have in common?
My brain, pre learning:
STIMULUS 1 RESPONSE 1
(Shakespearean sonnet) (ennui)
My brain, post learning:
STIMULUS 1 RESPONSE 2!!!!!
(Shakespearean sonnet) (happiness!)
Learning is the association of
stimuli with new responses.
How does learning occur?
Our brain has about a hundred billion
neurons, but we do not grow new ones
Instead , learning happens at the connection
point between different neurons—at the
How can neurons
make new synapses
Releasing more vesicles
More receptors for
In this picture, there are 3 things happening to
strengthen this synapse. Can you find them?
Dopamine is a particular neurotransmitter with
many roles in the brain, including:
- Cardiovascular and renal control
- Movement and balance
- Reward and addiction
- Pleasure, emotion
- Normal cognitive function (thinking)
Dopamine and disease
Dopamine deficiency in certain parts of the
brain is related to Parkinson’s and motion
Excessive dopamine has been linked to
schizophrenia and delusions.
Mechanisms of Drug Action
A dopamine agonist would bind to receptors instead
of dopamine and convince your neurons that
dopamine was there.
A dopamine antagonist would bind to receptors
instead of dopamine and block normal activation.
Other drugs inhibit reuptake, leaving more
dopamine in the synapse longer. (cocaine)
Indirect drugs cause extra dopamine release from all
Neurotransmitters convey “messages” across the synapse
Dopamine and Reward
Dopamine is involved in a brain circuit often
called the “reward pathway”
In studies, we observe dopamine release
when subjects are rewarded with
Generally, more dopamine is released when
the reward is unpredicted
Dopamine/Opioids: Brain’s incentive reward systems
Activation of reward center produces a “wanting” and “liking”
Some drugs activate your reward systems since they act
on the same receptors
Drugs make your brain really happy…..
Normal Brain Brain on Drugs
BUT only when your brain is on drugs.
0 1 2 3 4 5 hr
Time After Amphetamine
0 1 2 3 4 5 hr
Time After Cocaine
0 1 2 3 4 5hr
Time After Morphine
0 1 2 3 hr
Time After Nicotine
DiChiara and Imperato, PNAS, 1988
Effects of Drugs on Dopamine Release
Repeated use of drugs trigger compensatory processes
and saturate the brain’s reward systems
individual can become conditioned/habituated/adapted to
the intense level of drug-induced pleasure
the normal level of natural rewards are no longer
experienced as very pleasurable
this is caused by synaptic changes—just like learning!
Too much dopamine activation at the synapses leads your
neurons to decrease the number of receptors.
Brain on drugs after
Brain on drugs for
an extended period
Chronic drug taking ….reorganizes the liking
and wanting systems
… drugs may no longer be pleasurable but you still want them…
Drugs can change your brain so that natural events are no longer
DA Receptors and the Response to
As a group, subjects with low receptor levels found MP pleasant
while those with high levels found MP unpleasant
Adapted from Volkow et al., Am. J. Psychiatry, 1999.