Task 4 Flashcards
4.1: Which structures are part of the reward system?
fornix, cingulate cortex (CC), parahippocampal gyrus, hippocampus, amygdala, hypothalamus, septal nuclei, mammillary body
4.1: Motivational/Limbic loop in BG –> which structures involved?
ACC, mOFC, ventral striatum, SNr/GPi (limbic territory)
4.1: Mesolimbic dopa pathway
VTA –> nucleus accumbens
4.1: Mesocortical dopa pathway
VTA –> Frontal cortex
4.1: Similarity limbic & motor loop
limbic: stimulus –> outcome
motor: stimulus –> response
- -> both prioritize stimulus with highest outcome & resolve competition between different reward/ motor programs
4.1: Similarity limbic loop & ballot model
both compatible with ballot model; vote for/against stimuli
4.2: What does tonic DOPA mean?
-DOPA neurons are continuously active
4.2: What does phasic DOPA mean?
- DOPA neurons are active in phase ( on – off – on – off - …)
- Phasic activation = burst activity
4.2: Where does DOPA come from?
- Input: from VTA & NA (nucleus accumbens)
- -> From VTA: connected to primary rewards (e.g. food)
- -> From NA: connected to secondary rewards (e.g. money)
4.2: Where does DOPA project to?
DLS (=dorsolateral striatum) & VMS (=ventromedial striatum)
4.2: What does DOPA signify?
-reward neurons –> midbrain DOPA-mediated signals the pure reward of objects
When do midbrain DOPA neurons exhibit phasic activity after?
following primary food & liquid rewards
4.2: When else is DOPA released?
-after prediction error
-show phasic activation following conditioned visual, auditory & somatosensory reward-predicting stimuli
==> signals reward & reward prediction
4.2: How does DOPA respond to a positive reward prediction error (smth unpredicted)?
phasic activation
4.2: How does DOPA respond to a neutral reward prediction error (completely predicted)?
no response of DOPA
4.2: How does DOPA respond to a negative reward prediction error (lower than predicted)?
depression
4.3: How does a conditioned inhibition paradigm work?
test stimulus is presented simultaneously with an established reward-predicting stimulus, but not reward is given afterwards –> test stimulus predicts absence of rewards (conditioned inhibitor)
4.3: Conditioned inhibition paradigm: omission of reward after conditioned inhibitors–> DOPA response?
does NOT lead to a prediction error or response in dopaminergic neurons
4.3: Conditioned inhibition paradigm: occurrence of reward after conditioned inhibitors–> DOPA response?
strong positive prediction error = enhanced activation of dopaminergic neurons
4.3: How does the blocking paradigm work?
stimulus is not learned as a valid reward-predicting, conditioned stimulus if it is paired with an already fully predicted reward
4.3: Blocking paradigm: absence of reward after blocked stimulus–> DOPA response?
NO prediction errror –> NO DOPA response
4.3: Blocking paradigm: reward after blocked stimulus–> DOPA response?
positive-prediction error –> DOPA response
4.3: What does time sensitivity & context dependency of the DOPA signal mean?
- time sensitive: very high –> DOPA neurons are not activated by reward-predicting conditioned stimuli that are predicted by another stimulus with a time course in a range of seconds
- context dependency:
4.3: How do DOPA neurons react to neutral stimuli
combined with rewards?
–> after reward?
–> after cues predicting absence of rewards?
- phasic activation after conditioned reward-predicting stimuli –> response proportional to the subjective value of reward predicted by the stimuli
- depressed activity for cues predicting the absence of rewards
- 3: How do DOPA neurons react to alerting stimuli?
- -> physically intense stimuli?
-Physically intense stimuli: induce activation of dopaminergic neurons, which is enhanced by stimulus novelty
4.3: Which kind of events do DOPA neurons have a combined sensitivity to?
to rewarding & physically salient events
4.3: How do DOPA neurons react to aversive stimuli?
respond mostly with depression to aversive events
- 3: How do DOPA neurons react to aversive stimuli?
- -> Time course
- Slower responses in comparison to reward related activity
- responses start slowly & last for several seconds
- 3: How do DOPA neurons encode reward uncertainty?
- -> which pattern of activation?
- -> at postsynaptic level?
- 1/3 of DOPA neurons show a low, sustained &moderate activation between reward-predicting stimuli & reward
- At postsynaptic level: low DOPA concentrations appropriate for stimulating D2 receptors (high affinity)
- -> highest at 50/50 chance
4.4: Which range of stimuli can elicit a (primary) phasic dopamine response in humans?
unconditioned, biologically & evolutionary relevant stimuli, e.g., food, water, sex
4.4: Why is in reward selection tasks the
actual reward often made somewhat different from the reward that is promised to the participants (RPE)?
-Reward precidtion error –> DOPA response
4.4: Why is this manipulation not necessary in a complex cognitive task, where the reward is feedback information on how well the participant did on each trial?
o Info about correctness of an answer –> acts as a generalized conditioned reinforcer
o task itself & its successful performance can be rewarding ==> cognitive feedback alone can be enough of a reward
- RPE: you can’t predict which feedback you get –> kind of social approval (you can never predict cognitive feedback 100%) ==> pp are never 100% sure if they performed correct
4.4: At which 2 points during learning do DOPA neurons respond?
- If reward predicting stimulus is detected –> dopa burst OR
- If reward is delivered –> dopa burst
4.5: What does phasic dopamine has to do with addiction & self-stimulation?
any stimulation that increases phasic dopamine in the ventral striatum is addictive (example:self-stimulation experiments in animals)
- 5: Willuhn et al’s (2012) experiment on development of addiction
- -> AIM
to investigate neural substrates underlying development of drug abuse
- 5: Willuhn et al’s (2012) experiment on development of addiction
- -> METHODS
- Longitudinal neurochemical recordings of 3 weeks
- Rats got implanted with catheters that facilitated cocaine administration
- If they poked the accurate key, cocaine got directly administered
- 5: Willuhn et al’s (2012) experiment on development of addiction
- -> RESULTS
- phasic DOPA release where?
- which signal declined& which emerged?
- phasic DOPA release in the VMS & DLS after the operant response for drug
- -> VMS signal declined & DLS signal emerged during the progression of the drug taking
- 5: Willuhn et al’s (2012) experiment on development of addiction
- -> which parts of the striatum are required when?
- VMS is required for the first phase of addiction (= feedback-based, cocaine reinforced learning)
- DLS is required when this feedback-based learning is not necessary anymore
4.5: What happens when the VMS is lesioned in rats regarding the development of addiction?
Lesion in VMS –> prevents the development of phasic dopamine signalling in DLS
4.6: What’s the relationship between reward, motivation & habits?
-motivation starts with the urge to obtain a particular goal, or the wanting of that goal –> usually a reward (or a drug)
-While pursuing the goal, the organism learns what cues in the environment signal the availability of the goal/reward, what action bring the goal closer &
what leads to consumption
-These cues & actions become habits that start to get control over the behavior of the organism
-After a while, it is no longer the desire for the goal (LIKING), but these cues & habits that drive the organism to the consumption of the drug (WANTING)
4.5: Willuhn’s study –> DOPA antagonist
-one group: dopa antagonist in first week & the other in third week ==> In both groups: led to more cocaine consumption
- third week: also more poked to control poke (so alsopressed non-drug key)
-first week: more pokes that got cocaine
==> DLS important for effective plan on how to get drugs; important for behaviour specification (¬ about more consumption)
4.1: Nigrostriatal DOPA pathway
Substantia nigra –> thalamus –> striatum
