PSYC20006 Lecture 20: Lecture 20 - Dopamine & Desire
12 Jun 2018
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Lecture 20 - Tuesday 16 May 2017
PSYC20006 - BIOLOGICAL PSYCHOLOGY
LECTURE 20
DOPAMINE & DESIRE
TODAY
•Dopamine pathways & synthesis
•Dopamine & Parkinson’s
•Dopamine & Reward
•Dopamine & Cognitive effort
•Dopamine & Addiction
DOPAMINE PATHWAYS &
SYNTHESIS
•Breakdown of something acting as dopamine
becomes NA. Hardly surprising.
•Many different drugs that affect the broader
dopaminergic systems. A particular one is L-
Dopa, and was important in the initial
understanding of dopamine pathways. It is
basically a synthetic version of Dopa.
•Can semi-temporarily release people from
Parkinson’s paralytic states. Eventually the brain
pathways got used to the drug though.
DOPAMINE & PARKINSON’S DISEASE
•Caused by death of dopamine cells in the Substantia
Nigra.
•Disease initially characterized by motor tremor.
Later symptoms include cognitive impairments and
dementia. Symptoms often includes reduced
“executive function”.
•There is currently NO CURE of the disease, but
symptoms can be reduced through drugs and deep
brain stimulation.
•Treatment of the disease can cause impulsivity,
hypersexuality, gambling, addictive like behaviours
(see section on Reward & DA).
Lecture 20 - Tuesday 16 May 2017
PSYC20006 - BIOLOGICAL PSYCHOLOGY
REWARD PREDICTION ERROR
•Diagram 1: After the reward, there is an
increase in the likelihood with which this
particular neuron fires.
•Diagram 2: if at a predictable interval there is the same
reward. The animal highly expects the reward. It is also
important thinking that the animal is just bored and stuff
and it is not the case that the beep is happening at a
highly predictable 20 second intervals.
•The idea is that the beep becomes the positive
unexpected signal. But the fact that there is a reward
later is highly expected.
•Diagram 3: the beep is still unexpected, and all of a
sudden there is no reward. Here, we see a suppression of
the dopamine neurons at the time. It is also coding for
worse than expected.
•Receiving money is a positive experience
(losing it is negative) but money is just
paper.
•We like money because we learn to
associate it with items or activity of value.
•If the gain or loss is unexpected the feelings
associated are often more intense (losing
money on the street/picking up money on
the street)
REWARD: REAL & VIRTUAL
•Rewards can be
•Real (e.g. food or sex)
•Symbolic (e.g. money)
•Virtual (e.g. points in a game)
•DA is involved in all cases.
COGNITIVE CONTROL &
REWARD
•It is currently unclear why attention and
cognitive tasks are “effortful” and why task
engagement is aversive (our brains are also
very active when we relax or watch TV).
•The feeling of cognitive effort seems
particularly linked to working memory
and “cognitive control”
•It is proposed that DA codes both goal
reward and effort costs and that the
aversive feeling of cognitive effort reflects
”opportunity cost”
•Task persistence is justifiable only while
progress outpaces accruing costs.
COGNITIVE EFFORT & REWARD
•Cognitive tasks with low success are particularly unpleasant (it feels like a waist of time) and
might bias someone towards disengaging and selecting the low-cost “guess” option.
•Opportunity costs = everything else rewarding that you could be doing at this time.
Document Summary
Today: dopamine pathways & synthesis, dopamine & parkinson"s, dopamine & reward, dopamine & cognitive effort, dopamine & addiction. Synthesis: breakdown of something acting as dopamine becomes na. Hardly surprising: many different drugs that affect the broader dopaminergic systems. Dopa, and was important in the initial understanding of dopamine pathways. It is basically a synthetic version of dopa: can semi-temporarily release people from. Eventually the brain pathways got used to the drug though. Dopamine & parkinson"s disease: caused by death of dopamine cells in the substantia. Executive function : there is currently no cure of the disease, but symptoms can be reduced through drugs and deep brain stimulation, treatment of the disease can cause impulsivity, hypersexuality, gambling, addictive like behaviours (see section on reward & da). Reward prediction error: diagram 1: after the reward, there is an increase in the likelihood with which this particular neuron fires, diagram 2: if at a predictable interval there is the same reward.
