Week 8: Reward and Motivation Flashcards
What is a Reward?
- a stimulus that elicits approach behaviour
- a reinforcer
- an unconditioned incentive
- strengthens the Stimulus-Reward relationship
What is a punishment?
- A stimulus that elicits avoidance behaviour
- the behaviour is being discouraged
- weakens the stimulus - reward relationship
What type of reinforcers can we distinguish?
Primary reinforcers vs. Secondary reinforcers
What characterises a primary reward?
- value is hardwired (benefit for survival fitness)
- value is state-dependent (subjective utility)
- e.g. food
What characterises a secondary reward?
- no intrinsic value
- becomes rewarding through association (is conditioned)
- e.g. money
What is the reward value?
The integration of all subjective factors indicating how much a stimulus is worth
What are the different subjective factors indicating the reward value?
- payoff (how much reward is offered?)
- probability (how likely is it to attain the reward?)
- effort / cost (how difficult is it to get the reward?)
- context (state-dependence)
- preferences (e.g. risk aversion, social values, etc.)
What is negative reinforcement?
Reinforcement due to removal of a consequence
What is the nigrostriatal pathway?
- from substantia nigra to striatum
- motor control
- death of neurons in this pathway can result in Parkinson‘s disease
What is the Mesolimbic Pathway?
- from VTA to Nucleus accumbens, amygdala, hippocampus and ACC
- emotional processing
- memory formation
What is the Mesocortical Pathway?
- from VTA to PFC
- Motivation
- Executive Control
- Impulsivity
Where is Dopamine produced?
- VTA and SNC
- NOT PFC
What can happen if mesolimbic and or mesocortical pathways do not function properly?
- hallucinations
- Schizophrenia
What is the Tuberoinfundibular pathway?
- hypothalamus to pituitary gland
- hormonal regulation
- maternal behaviour
- pregnancy
- sensory processes
What does state dependency mean?
Subjective utility
what is the nucleus acumbens?
Located at the intersection of caudate nucleus and putamen in basal ganglia
What is the OFC?
- The Orbitofrontal Cortex is a zone of convergence from multiple modalities
- Represents values and hedonic/affective reactions to motivational stimuli
How do OFC lesions affect behaviour?
- monkeys with OFC lesions choose nonfood items much more frequently
- Failure to adapt choice behaviour when previously rewarded item stops being rewarded
how do medial and lateral OFC differ in the context of rewards?
Medial OFC: increasing activity with increasing reward
Lateral OFC: decreasing activity with increasing reward
What is the Rewarding Stimuli Study?
- contrast pleasant with unpleasant stimuli
- Sites of activation for different stimuli are seen
- Shows that
- OFC plays relevant role in human processing of rewarding stimuli
- Reward is coded largely independent of modality
How does classical conditioning work?
- Before conditioning
- unconditioned stimulus (food) results in unconditioned response (salivation)
- Neutral stimulus (tuning fork) results in no conditioned response (no salvation)
- During conditioning
- tuning fork + food result in unconditioned response (salivation)
- After conditioning
- conditioned stimulus (tuning fork) results in conditioned response (salivation)
- Before conditioning
what is the difference between primary reward anticipation versus the receipt?
- midbrain and striatum already active during anticipation of reward → evidence for wanting
- Not clear what the correlate of hedonist pleasure is because its conflated with expectation
- Receipt in insula
What is the reward prediction error?
- No prediction, reward occurs: dopamine spike after reward
- Reward prediction, reward occurs: dopamine spike just after conditioned stimulus (not after reward)
- Reward predicted, no reward occurs: dopamine spike after conditioned stimulus and drop after no reward occurs
What are implications of reward prediction?
- if dopamine mediates pleasurable aspect of reward itself → predictive nature of dopamine signals, → pleasurable experience has shifted forward in time to the cue
- Or: dopamine system might mediate incentive salience of stimuli → separate brain mechanism for hedonistic aspects of reward required (wanting vs liking)
What does dopamine do in the context of motivation and reward?
- regulated the motivation to pursue a reward
- A brain without dopamine can enjoy something but will not pursue it
- Dopamine is the rewarding chemical
- Is produced when:
- Completing a task
- Self-care activities
- Eating food
- Celebrating little wins
What is Oxytocin and when is it released?
- the love hormone
- Released when
- Playing with a dog or baby
- Holding hands
- Hugging loved ones
What is Serotonin and when is it released?
- the mood stabiliser
- Is released when:
- Sun exposure
- Meditating
- Running
- Being in nature
What is Endorphin and when is it released?
- the pain killer
- Is released when:
- Laughing
- Excercising
- Dark chocolate
- Essential oils
What is the difference between wanting and liking?
wanting
- „incentive salience“
- approach
Liking
- „hedonistic“
- Affective
- Taste reactivity in oral cavity independent of approach behaviour
does dopamine mediate wanting or liking?
dopamine receptor blockers can stop consumption but leave hedonistic value intact
→ dopamine mediates wanting rather than liking?
What is delayed gratification?
marshmallow test
What is temporal discounting?
- Preferred to select small but immediate reward over larger but more delayed one
- When the delay is very short, subject typically selects larger reward
- Neurons in VTA are active during discounting behaviour
- discounted value of reward curve measures how much immediate reward (smaller sooner) the variably delayed constant reward (larger later, constantly 100%) is worth
- Point of subjective equality = where probability of SS and LL is the same = where they have the same value
