L.2 - Drug Habits, Cognitive control and neural basis Flashcards
1
Q
What are the learning objectives?
A
- Distinguish between goal-directed action and habit based on their definitions [paraphrasing and analyzing]
- Explain how habits are formed according to the ‘Law of Effect’ [paraphrasing], and explain the ideal conditions for forming a strong habit [evaluating]
- Explain how to experimentally test whether a behavior is goal-directed or habitual [paraphrasing], and identify the essential features of this experimental paradigm [analyzing]
- Apply the ‘outcome devaluation’ paradigm to a new research question regarding targeted/automatic control. Be able to adapt it for a specific research question, but at the same time maintain the essential features of the paradigm [independent thinking]
- Explain what the dual-system theory of instrumental behavior entails [paraphrasing] and compare the role of the two systems in behavior [analyzing]
- Define ‘cognitive dissonance’ and explain how this could affect the interpretation of one’s addictive behavior [analyzing]
- Describe the neural basis of goal-directed actions and habits in humans [paraphrasing]
- Explain in what ways habit theory of substance abuse has implications for its treatment [analyzing]
- Name and define the main executive (i.e., cognitive control) functions [paraphrasing], name their measures [paraphrasing], explain how these are used to measure cognitive functioning, and describe evidence for the role of these functions in substance abuse [independent thinking]
- Critically evaluate the role of craving, habits and executive functions in compulsive drug seeking and relapse, using arguments on both a behavioral and neuroscientific level [evaluating and independent thinking]
- Be able to offer 3 arguments against and 3 in favour of the brain disease model of addiction [evaluating and independent thinking]
- this final learning objective can be achieved on the basis of the material covered in Module 1, Module 2 and tutorial 1. Following the tutorials a knowledge clip with arguments for and against will be uploaded to the Study Material of Module 1
2
Q
Outline of the lecture
A
- Introduction habit account of addiction
- Measuring habits and neural basis
- Research into drug habit
- Outstanding questions
3
Q
- Introduction habit account of addiction
Pavlovian vs instrumental conditioning
A
Pavlovian/Classical conditioning:
- change in behavior due to experience with a relationship between a neutral conditioned stimulus (CS) and a motivationally relevant unconditioned stimulus (US)
→ does not explain SUD well
Instrumental conditioning:
- change in behavior caused by a relationship between an instrumental response (R) and a motivationally relevant outcome (O)
> rewards and punishments & likelihood of action repetition
4
Q
Operant conditioning
- what are the four different possible situations?
A
(see picture)
- if response is followed by reward, you’re more likely to repeat behavios
- if followed by punishment, less likely to repeat behavior
1- Reward (positive reinforcement- behavior leads to positive event→ behavior increases)
> e.g. working for the rewarding effect of drugs
> e.g. reiforcing abstinence with vouchers/monetary incentives (contingency management)
2- Punishment (behavior leads to negative event→ behavior decreases)
3- Omission (behavior prevents positive event→ decreases)
4- Avoidance & Escape (negative reinforcement - behavior prevents negative event→ increases)
> avoiding withdrawal symptoms or escaping from negative feelings
! can be goal-directed or habitual
5
Q
what is a goal-directed action?
→ how are they learnt?
A
- instrumental behaviors that are only performed when someone has a certian goal and believes that this behavior will increase the likelihood of reaching that goal
→ learnt as a consequence of causal relationship between the action/response (R) and its outcome (O) - it can turn into a habit when repeatedly performed
6
Q
Goal-directed drug seeking vs Habitual drug seeking
- how can drug seeking be considered goal-directed?
A
- craving drives instrumental drug-seeking behavior
- addict’s brain is more sensitive to the rewarding value of substances of abuse (compared to social or food rewards)
- “goal-directed” when based on expectaction (cognitive criterion) and positive (hyper)evaluation (motivational criterion) of the drug
- “goal conflict”→ arise from extremely positive short-term goal of the drug’s rush and/or suppression of withdrawal symptoms (overshadows long-term goal of health)
7
Q
What is the empirical support behind it?
A
- drug use is associated to positive subjective experience of drug, positive expectations and willingness to pay for it
- instrumental tasks shows that people with addiction work harder for drug rewards than non-addicts
8
Q
What are the Belief and Desire criteria?
A
Anthony Dickinson
- The (cognitive) Belief Criterion
> performance is mediated by knowledge of the causal relationship between the action and its outcome
> the behavior is based on the belief that that action will lead to a specific outcome - The (motivational) Desire Criterion
> performance is mediated by a representation of the current goal of incentive value of the outcome
> goal directed action is only performed if the expected outcome is desirable
9
Q
How can drinking be considered goal-directed?
how does it go from goal-directed action to habit?
A
- e.g. you get a drink at the end of the working day, to relax
! if you do it everyday, then it can become a habit
→ you do it automatically, it’s not goal-directed anymore but it’s activated by situation and environment of that moment
10
Q
Goal-directed drug seeking vs Habitual drug seeking
What is a Habit?
A
- Instrumental responses that are triggered by stimuli
- do not depend on the current motivation for the outcome of the behavior
11
Q
are habits adaptive?
why?
A
- habits are evolutionarly adaptive
> they can be exectuted fast and efficiently
> habits free up cognitive resources, therefore allowing us to attend to other important matters
12
Q
how can drug seeking be considered habitual?
A
- drug seeking starts out as goal-directed but becomes increasingly driven by aberrantly strong habits
- Law of effect (Thorndike)
13
Q
What is the Law of Effect?
+ by who and when?
A
- Thorndike, 1911
- habits are formed when a behavior is followed by reward (positive reinforcement) or by the absence of an expected negative event (negative reinforcement)
> the strengthening of the stimulus-response association leads to the gradual build-up of a habit - the reward (or relief) reinforces a stimulus-response (S-R) association between environmental stimuli and behavior
> this means that if the stimulus is encountered, it can immediately trigger the old behavior, even when one is currently not particularly motivated towards the outcome - the occurrence of an aversive outcome should weaken the S-R associations
14
Q
Habit formation
How are habits formed?
A
- when we repeat behavior in certain context, and the behavior is positively reinforced, then it will lead to the gradual building-up of a stimulus-response association
> repeated behavior in specific context + positive reinforcement = stimulus-response assocaition - not actively anticipating outcome
15
Q
what is the Habit Discontinuity Hypothesis?
A
- habits are contextually dependent
- S-R habits can be disrupted by a change in context
> this provides a window of opportunity for adapting behavior in light of one’s current goals
16
Q
what is a common way to study habits?
→ what are the issues with that?
A
- diary studies
> goal pursuit and behavioral repetition are heavily intertwined
> there may be differences in the daily environments of the participants
> participants may not be fully aware of habitual behavior to report it objectively
17
Q
Goal-directed control vs Habit
A
Goal-directed control
- Flexible
- Belief criterion (behavior comes because of the outcome that we believe will follow the action)
- Desire criterion (behavior comes because of the desirable expected outcome)
Habits
- efficient
- behaviorally autonomous
> stimulus dependent: under external stimulus control
> goal independent: takes place independently of the desirability of the outcome
→ only goal-directed actions are mediated by the knowledge of R-O associations, and by an evaluation of the anticipated outcome in light of one’s current motivation
= (goal-driven actions happen when someone knows what their action will lead to, and they think about whether they still want that result based on how they feel right now)
18
Q
what is the dual-process instrumental action?
A
- shift from flexible, goal-directed crontrol towards inflexible, efficient habitual behavior
> through repetition, fatigue, low working-memory, - both processes are very functional in real life (apart from maladaptive habits)
! the S-R associations can gradually become dominant after many repetitions, shifting the balance from flexible, goal-directed control towards S-R habits
19
Q
what study proved the importance of habits + the context dependency?
A
= The popcorn experiment
- field study (cinema): Neal et al. 2011
- on a 7-point scale, participants indicated how frequently in the past they ate popcorn in movie theatres (always→never)
- half the participants got fresh popcorn, half got stale popcorn
- after the movie, experimenters measured the amount of popcorn eaten by each participant
! experiment also repeated in meeting room context
20
Q
Popcorn experiments- the results
A
Cinema context
- low and moderate habit participants→ stale < fresh
- high habit participants→ stale = fresh
Meeting room context:
- all participants→ stale < fresh
(see picture 2)
21
Q
Is addictive behavior goal-directed or habitual?
A
can be both!
- drugs are often used in ritualistic manner
- “slips of action” suggest absent-minded drug use
> e.g. lighting cigarette when ban was first started
22
Q
can habits also drive compulsive drug seeking?
A
- depends on who you ask
> Berridge & Robinson→ NO
> Everitt & Robbins→ YES
23
Q
Incentive-sensitization theroy - berridge & robinson
A
- Berridge & Robinson
- a pathological motivation for drugs (+ impaired cognitive control) is the core problem in addiction
- habits do not play central role in addiction → compulsive drug seeking is NOT a habit
> habits are absent-minded behavior, slips of action, but they do not explain compulsive urge to use drugs
24
Q
What does the incentive-sensitization theory say about addiction?
A
Addiction is driven more by “wanting” (craving) than by “liking” (pleasure)
- sensitization of wanting system (dopamine system)
> drug cues trigger an intense craving/incentive salience
25
Habit account
- Everitt & Robbins
- aberrantly strong habits (+ impaired cognitive control) mediate the transition from goal-directed, recreational substance use towards compulsive substance abuse
- habits are at the core of compulsive drug seeking
26
What is central to seeing compulsive drug seeking behavior as habitual?
1) there are individual differences in the tendency to form dominant habits, and with a strong tendency, the person in question is vulnerable to developing an addiction (or other compulsive behavior)
2) drugs are extremely strong reinforcers of S-R habits
3) drugs lead to structural changes in the brain, that lead to a generally stronger tendency to rely on habitual control
(picture 21)
27
Dual-process instrumental action
- what are the two perspective of the effect of drugs on the brain?
(in relation to the perspectives of goal-directed control and habit)
Goal-directed control
- chronic drug abuse has neurotoxic effects on prefrontal cortex in particular
> this could lead to decreased goal-directed control + related cognitive control functions
Habit
- drugs are strong reinfocers of habit formation, due to their direct effect on the dopamine system
28
Dual-process models
- what is the main concept?
- these models explain drug habits, as a result of two disrupted processes
1. reinforced automatic, reflexive, impulsive bottom-up processes
> e.g. Pavlovian conditioning, formation of instrumental habits, ...
2. weakened, top-down cognitive, executive, reflective functions
> e.g. goal-directed control, cognitive/executive control functions (e.g. error monitoring, decision making, impulse control)
→ impaired cognitive control can lead to a fall back on habits
29
what are dual-processes models supported by?
- neuroscientific research
> it shows that goal-directed actions and habits are driven by different brain systems
30
what are the neuronal pathways of drug using?
(see picture 3)
1. Initial drug use
- craving and goal-directed drug-seeking
> PFC, mesolimbic dopamine pathway
2. Drug habits
> Nigrostriatal dopamine pathway
> substantia nigra (SN)→ posterior putamen
3. Drug abuse / addiction
- compulsive behavior
> PFC dysfunction
the habit account of drug use takes into consideration the mesolimbic dopamine pathway for craving and goal-directed drug-seeking, but it is considered the first step to habit formation
→ there is a shift from mesolimbic dopamine pathway to nigrostriatal dopamine pathway
31
the Substantia Nigra
- what/where is it?
+ characteristics
- there are two substantiae nigrae, one on each side of the midline of the brain
> substantia nigra pars compacta
> substantia nigra pars reticulata
- most of the dopamine-producing neurons of the brain are found in either the substantia nigra, or in the Ventral Tegmental Area (vta)
- it is part of the basal ganglia, together with the striatum (caudate + putamen)
! one of the main functions of the S.N. is movement
→ death of dopamine neurons in substantia nigra is associated with movement-related deficits
32
the nigrostriatal pathway
- what is it?
(see picture 22)
- the dopamine neurons in the basal ganglia (caudate, putament and substantia nigra) make up the nigrostriatal pathway
- the n. p. is a large bundle of fibers
> this is one of the major dopamine pathways in the brain
> important for the facilitation of movement
33
what are the three dopamine pathways?
(picture 4)
- Mesolimbic
> VTA → NAcc
- Nigrostriatal
> SN → posterior putamen
- Mesocortical
> VTA → PFC
VTA: ventral tegmental area
NAcc: nucleus accumbens
SN: substantia nigra
34
MC question 1
Heroin use was prevalent amongst american soldiers in vietnam. Fortunately, treatment was surprisingly succesful. Few soldiers relapsed after returning home:
- Which theory can account for the lower relapse rates in Vietnam soldiers compared to the relapse in individuals returning from a drug rehab center where they were treated for heroin use?
A. Incentive-sensitization theory
B. Habit theory
C. Both
D. Neither
C. Both
- when people return from a rehabilitation center to the home environment in which they used to take drugs, drug craving and seeking can be triggered again by cues in the environment
- in contrast, for the Vietnam soldiers, their home environment was not associated with the drug US and drug seeking
- Habit account: heroin reward (or relief from withdrawal)
- Incentive-sensitization account: due to neural sensitization, drug-associated cues elicit aberrantly strong wanting
35
MC question 2
Who are the authors of the habit theory of addiction?
A. Everitt & Robbins
B. Leshner & Volkow
C. Berridge & Robinson
D. Wiers & Field
A. Everitt & Robbins
36
Outline
2. Experimental measure of habits and neural basis
37
What is the outcome-devaluation test?
- experimental paradigm that is used to determine whether a certain behavior is goal-directed or habitual
- consists of three phases
1. instrumental learning phase
2. outcome deviation phase
3. critical test phase (extinction)
38
How can the outcome devaluation paradigm be applied in animal studies?
~~~~RATS!~~~~
(picture 6)
1. Instrumental learning phase
- rat is trained to press the lever in order to get food
2. Outcome devaluation phase
- they adjusted food desire (e.g. by inducing nausea or via satiation)
> e.g. the rat is put in another room with as much food as he wants, and he becomes satiated (outcome is devalued)
3. Critical testing phase (extinction test)
- Did the rat take long to stop pressing the lever?
~ if it's goal-directed, rat should stop pressing the lever immediately
> the rat would anticipate the delivery of food, but he doesn't want food anymore so he would not press the lever
~ if it's habitual, it will take longer for the rat to stop pressing lever
> the contextual stimuli would reactivate the response through a stimulus-response association, even when the reward is no longer valuable
> the rat would then not be able to flexibly adapt its behavior (and would continue to press lever for the devalued food)
39
what role does extinction play in the outcome devaluation paradigm?
- why?
- this paradigm is carried out in extinction, which means that when the rat presses the lever, he receives no food
Why?
- if the food gets delivered, we can't determine whether it's habit or goal-directed activity
> the Law of effects says that habits are strengthened when response is followed by reward, but weakened when not followed by rewarding outcome
> therefore, offering a devalued outcome duering the testing phase would therefore be predicted to gradually lead to weaker S-R associations (compared to when valuable outcome is offered)
> this means that if the test is not performed in extinction, it is impossible to tell what it means when the rat presses less for devalued outcome
= if the rat then immediately (without further opportunity for learning) adjusts it's behavior, we know that it acts in a goal-directed manner (based on anticipation and evaluation of the outcome)
40
"Conducting outcome-devaluation test in extinction is done to prevent learning based on the new outcome value"
- how can this answer be explained?
- Law of effect
(when behavior is followed by reward, it will strengthen mental association between environmental stimuli and behavior; when followed by punishment, association is weakened)
- if you present food in test phase, the goal-directed account and habitual account explain the behavior; association will be strenghened
- if don't present food (outcome) anymore, the rats would go in extinction (of learning) and stop responding, regardless of the value of the outcome
→ we need to keep test short otherwise the behavior will extinguish
- if rats adjust quickly the behavior, this can be associated to what rats learnt before in instrumental learning phase, as opposed to new learning in testing phase
41
Why are extinction tests kept short?
The behavior will extinguish naturally, with enough testing time
42
what are the result of the outcome devaluation paradigm?
- what do the graphs show?
(picture 7)
Graph 1: goal-directed behavior
> more lever press for the valuable food compared to the devalued food
> this is the case after shirt instrumental learning phase
Graph 3: habitual responding
> no significant difference in responding for the two foods
> longer instrumental learning phase
> rats perseverate when outcome is devalued
43
MC question 3
What is the primary reason for conducting outcome-devaluation test in extinction?
A. to prevent food waste
B. otherwise rats will press so much that they become tired
C. to prevent learning based on the new outcome value
D. otherwise rats will become satiated
C. to prevent learning based on the new outcome value
44
Repetition vs Context
What does the outcome devaluation paradigm ultimately say?
- Repetition: overtraining leads to insensitivity to outcome devaluation or "behavioral autonomy"
- Context: insensitivity to outcome devaluation due to overtraining is context-specific
= overtraining→ insensitivity to outcome devaluation (context-specific)
- e.g. popcorn experiment shows importance of context, together with other rats studies
> when context changes, even if animal is overtrained, the behavior will be sensitive to outcome devaluation
45
what is the role of overtraining in habit formation?
(outcome-devaluation studies)
- extensive overtraining diminishes the effect of devaluation on performance
> after moderate training (100 lever presses), devaluation of outcome (food pellets) decreased responding
> after extensive training (500 lever presses), rats continued pressing lever for food
! this insensitivity did not reflect ineffectiveness of the aversion procedure
→ behavior repetition renders behavior habitual in the sense that it is no longer dependent on the current desirability of the outcome
46
Outcome devaluation paradigm in humans
- experiment + neuronal finding
1. Instrumental training
- humans had to press either left or right key when looking at each image
> depending on pattern shown on the screen, pressing a certain key will be rewarded either with smarties or fritos
> left key: m&ms
> right key: fritos
- moderate training group: 2 brief training sessions on 1 day
- extensive training group: 4 sessions a day, for 3 days (for overtraining effect)
2. Devaluation by satiation
- one food devalued by satiation (either m&ms or fritos, randomly assigned)
3. Extinction test
- asked to eat as much as they could, until they did not find it pleasant anymore
- went to test phase where they were asked to press the keys to obtain snacks
+ Likert scales for hunger and pleasantness of food
(see picture 8)
(this paradigm is not as clear in humans as in animals)
47
what were the results of the M&Ms and Fritos experiment?
- moderately trained group was sensitive to the current outcome value
- extensively trained group was not affected by the current desirability of its outcome
> e.g. participants satiated on M&Ms still tended to persist in responding for this food reward
! after overtraining, an increase in activity was observed in putamen
48
what are the response and neural results of the M&Ms and Fritos experiment?
Response
- after minimal training, participants reduced their response rates during presentation of the cue linked with the food that they no longer wanted, but response remained high for food they still found pleasant
- after extensive training, the outcome sensitivity was not present (response rates did not differ significantly depending on the value of the outcome)
- after 2 sessions, behavior still goal-directed; after 12 sessions, habitual
Brain
- great activation of posterior putamen for development/control of habitual behavior
- within-day increase in task vs rest cue sensitivity
→ this suggests the resurgence of goal-directed behavior relative to habitual behavior at the beginning of task performance each day
+ cumulative effect of multiple days of training on activation of habitual brain areas
(+ DLS in next flashcard)
- vmPFC associated to goal-direceted behavior and involved in anticipation of upcoming reward
> vmPFC does not diminish with training→ this shows that habitual behavior comes not because we don't anticipate rewards anymore, but because the DLS has stronger effect on behavior (after training)
> circuitries of vmPFC and DLS are simultaneously engaged, and compete in control of behavior
49
what did this study show about the transition from goal-directed to habitual behavior?
- highly dynamic
- early phases of habitual behaviors start occurring when behavior is still considered goal-directed
- recruitment of DLS increases gradually with training
> e.g. slight non-significant increase in DLS activation on second day compared to first
> only with extended training the activation becomes strong enough
50
what is the strongest evidence for the dual process models?
- what does the evidence show?
- neural dual pathways, which support goal-directed and habitual behavior
- can be seen both in human and rats brain
> functional homologues: brain regions that evolved similarly in humans and rats, with same function
!! brain studies show that depending on the region of brain damage in animals, rats can be either more habitual (get habituated very quickly), or more goal-directed (do not habituate even after long training)
!! nigrostriatal dopamine pathway (SNc→striatum) disrupt habit formation
> responding remains sensitive to outcome devaluation after over-training
(see picture 9)
51
how can neural processes be studied in animals vs humans?
- animals: studying the effect of lesions and pharmacological manipulations on the outcome sensitivity of instrumental behavior
= allows for causal inferences concerning the involvement of different brain regions in habit and goal-directed action
- humans: measures of neuroimaging
= allows for correlations
52
how can the neural pathways be studied?
what did the studies show?
- Functional Magnetic Resonance Imaging (fMRI)
- trained people with strawberry juice or chocolate milk
= choices for the valued outcome were associated with activity in the ventromedial prefrontal cortex (vmPFC, partly overlapping with orbitofrontal cortex; OFC)
→ vmPFC very important for goal-directed control
(picture 10)
53
what are some important Brain areas involved in habit formation and goal-directed actions?
+ evidence
- premotor cortex, posterior Putamen & DLS → habits
- vmPFC , anterior caudate & DMS → goal-directed action
- nucleus accumbens → craving
> its response to reward presentation remains consistent through training → processes reward-related information even when behavior becomes habitual
(picture 11)
→ individuals with strong estimated white-matter connectivity between ventromedial prefrontal cortex and caudate tended to act better (more goal-directed) in slips-of-action test
→ strong estimated posterior putamen connectivity was negatively related with performance (consistent stimulus-cued responding for devalued outcome)
> high gray matter volume in posterior putamen was predictor of habitual control
54
how are animal lesion studies better than human neuroimaging studies?
- both lesioning studies in animals and neuroimaging studies in humans support the dual-process view (on instrumental action control), but animal research provides the strongest support:
> Causal evidence (as opposed to correlational)
> Challenge of capturing habits experimentally in humans (e.g. no replication of the over-training effect in
humans)
> Findings more consistent (animal lesioning>human neuroimaging)
55
MC question 4
Which subcortical brain region has been most strongly implicated in goal-directed action?
A. (Posterior) putamen
B. Ventromedial prefrontal cortex
C. Dorsolateral prefrontal cortex
D. Caudate
D. Caudate
- the caudate is a subcortical structure in the basal ganglia
- it is strongly implicated in goal-directed action
56
MC question 5
What paradigm can be used to determine whether drug seeking is habitual or goal-directed?
A. Progressive ratio paradigm
B. Pavlovian conditioned approach paradigm
C. Outcome-devaluation paradigm
D. Reinstatement paradigm
C. Outcome-devaluation paradigm
57
Outline
3. Research into drug habits
58
Where does most indirect evidence for drug habits come from?
What do they show?
+ example
- Cue reactivity studies (neuroimaging fMRI studies)
> show that pictures of drugs/alcohol activate the striatal habit region (~dorsal striatum)
- nucleus accumbens become active → craving
- dorsal striatum = posterior putamen (similar function; habits)
→ activation of habit indicated by scans, even though in the moment the participants do not perform behavior
e.g. when cocaine-addicted subjects are shown a video with cocaine cues during PET scanning, this leads to dopamine activity in the striatal habit region
59
what other indirect evidence do we have for drug habits?
- self report (Self-report Habit Index; SRHI)
→ asks about aspects that are thought to be central to habits
> e.g. Behavior X is something I do automatically / I do without thinking / I start doing before I realize it, ...
60
what are the pros and cons of SRHI?
-PRO: SRHI scores predicted the behavioral frequency of using each substance
-CON: this is a self-report measure, which relies on the ability to reflect upon the controllability and automaticity of drug seeking
→ therefore, we will turn to experimental research in animals and humans (outcome-devaluation)
61
what questions can the outcome-devaluation paradigm answer?
1. Does drug seeking become habitual with repetition?
2. Is habit formation accelerated for drug rewards relative to natural rewards?
3. Does substance abuse lead to a general tendency to fall back on rigid habits?
4. Are drug habits compulsive?
62
1. Does drug seeking become habitual with repetition?
1. istrumental training: rats trained to press lever to obtain alcohol
2. satiation (devaluation of the alcohol)
3. extinction test
- some rats have short-training (2 weeks); some have long-training (8-weeks)
- within each training group, half received cannulae implanted in dorsomedial striatum (DMS) and the other half in the dorsolateral striatum (DLS)
- GABA-antagonist Muscimol was injected through the cannulae immediately prior to the test
> this resulted in temporary inactivation of the DMS / DLS
63
what are DLS and DMS involved in?
- DLS→ habitual control
> lesions in this area disrupt the formation of habits
> rats with lesions here remained sensitive to devaluation even after extensive training
> habitual responding following extensive training became goal-directed again when DSL was temporarely inactivated
- DMS→ goal-directed control
> lesions impact acquisition and expression of goal-directed action
64
MC question 6
Which graph shows the test results for the group receiving long instrumental training (as opposed to short) + dorsolateral (vs dorsomedial) striatum inactivation?
(picture 12)
- graph D!
> rats that got the saline had no devaluation effect, as you would expect after long training
> when DLS was inactivated, the behavior becomes goal-directed again
! this study supports the idea that there is a transition from goal-directed alcohol-seeking behavior to a habit that is insensitive to devaluation
65
what does the graph show? (in detail)
what does it mean?
1. Saline / Devalued: High responding despite devaluation → suggests habitual behavior
2. Saline / Non-devalued: Also high responding → expected, since reward is still valued
3. Inactivation / Devalued: Significant drop in responding (* marked) → sensitivity to devaluation = goal-directed behavior
4. Inactivation / Non-devalued: Higher responding than the inactivation/devalued bar → again, expected
- With saline (control): The rats continue to seek the drug even after it's been devalued, suggesting habitual behavior has formed due to long training.
- With DLS inactivation: There's a clear drop in responding when the reward is devalued → this implies that inactivating the dorsolateral striatum disrupts the habitual system, revealing goal-directed behavior
66
main take-away of the study
Even after extensive training that promotes habit formation:
- DLS inactivation restores goal-directed control over drug-seeking behavior
- This supports the idea that the dorsolateral striatum is essential for habitual responding, especially in the context of addiction-related behaviors
67
2. Is habit formation accelerated for drug rewards relative to natural rewards?
Rat Study: compared food vs alcohol
→ devaluation of food caused larger devaluation than devaluation of alcohol
! this supports the idea that habit formation is accelerated with an alcohol reward
- accelerated habit formation was also found for cocaine
(picture 13)
68
3. Does substance abuse lead to a general tendency to fall back on rigid habits?
- the Fabulous Fruit Game
> participants learn to press keys in order to gain fruit coins, which are worth points (computerized experiment)
> fruits serve as outcomes and discriminative stimuli, in order to establish multiple R-O associations
- fruit on outside of box tells us what food we can earn on inside of box
→ grapes image outside the box indicates that if we press left lever we are rewarded with an orange and points inside the box
→ coconut image outside the box indicates that if we press right lever there are bananas and points inside the box
> e.g. if you see coconut and press left, you get an empty box and no points
- training description: Participants learn the correct response (right or left) for 6 different discriminative cues (pictures of fruit) to earn 6 different rewarding outcomes (pictures of fruit that were worth points)
(picture 14)
69
what are the phases of fruit experiment?
1. in instrumental training phase, people can build up stimulus-response associations (as explained above)
2. Devaluation
- some fruits are devalued by showing participants this picture (picture 15) [participants are instructed that some fruits no longer worth points]
→ apples and bananas are not worth points anymore
- test phase starts
3. Slips-of-Action test
> slip-of-action: habit intrusions; reveal habit learning in everyday life (e.g. you are going to uni by bike but turn right to go home, out of habit)
>under time pressure (shown pictures very quickly)
> very quickly decide whether to withold from pressing lever because coconuts are now not valuable anymore, or by habit you press it but lose points
! nominal extinction
70
Nominal extinction
- we don't give feedback during test, but we tell participants that we are still keeping the score
→ we tell them total score at the end of the test
(picture 16)
71
what role do Belief criterion and Desire criterion play in this experiment?
In order to do well:
- participants need to have knowledeg of the outcomes of their actions (belief criterion)
- participants have to base their decision to respond or not (go-no go) on the current oucome value (desire criterion)
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what are few concerns with this approach?
what was this concern mitigated by?
- symbolic outcomes and instructed devaluation fail to engage the basic learning mechanisms that we have evolved to optimise the pursuit of the biologically relevant events, like food
= When we’re told something isn’t valuable anymore (like through instructions or symbols), it doesn’t affect our behavior as strongly as real experiences do — especially when it comes to important things like food
> this concern was mitigated by the fact that the same neural substrates underlie responses to natural and symbolic reinforcers
73
what did similar studies show?
(picture 17)
- devaluation effect is reduced in people with history of cocaine
> no longer significant difference between valued and devalued outcome
→ this shows that addicts have a relatively strong (general) habit tendency
> this "habit tendency" could be due to strong habit formation, weak goal-directed control and combination of both
> but is habit tendency a consequence of drug use or a vulnerability factor?
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Alcohol and sugar experiment
- how was it carried out?
- chronic alcohol exposure leads to general habit tendency in animals
> Group Sugar: pressed for sugar for 2 weeks
> Group Sugar + : pressed for sugar for 8 weeks
> Group Sugar + and Alcohol: pressed for sugar for 8 weeks & received noncontingent alcohol (not dependent on making instrumental response, received anyway)
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Alcohol and sugar experiment
- what are the results?
- graph C shows Sugar and Alcohol group
(picture 18)
- in this setting, the 8 weeks were not sufficient to cause shift in habitual control for some reason, so no clear devaluation difference with two weeks group
- this graph shows behavior that looks the most habitual out of the three graphs
(picture 19)
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Amphetamine exposure study
- amphetamine exposure accelerates habit formation (for food rewards) in animals
> animals that were exposed to amphetamines show no devaluation effect in response to food reward
(picture 20)
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4. Are drug habits compulsive?
- rats experiment
- human translation
- rats were trained to self-administer cocaine (via direct intravenous administration)
- in the next stage, lever pressing occasionally led to an electric shock (while most of the time, lever presses were still rewarded with cocaine)
> after moderate training, punishment → drug seeking decreased
(cocaine is goal-directed action)
> after extensive training, a subgroup of rats continued working for cocaine even when they received electric shocks
! As in humans, this addiction-like behavior was present only in a small proportion of subjects using cocaine
(~20%)
! was predictive of relapse (or reinstatement) after withdrawal
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Summary
1. Drug seeking becomes habitual with repetition
2. Habit formation is accelerated for drug rewards relative to natural rewards
3. Substance abuse leads to a general tendency to fall back on rigid habits
4. Drug habits can be compulsive
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What are some critical notes regarding animal research on drug habits?
1. Most animal studies in the field of addiction are conducted in a highly impoverished context, in which only drug reward is available
> if you offer alternative natural rewards to drug (e.g. tasty food), it can break habitual drug seeking
> social play (with other rats) can be protective from development of habitual drug seeking
→ lack of social play in early life in animals increases the motivation to take addictive substances in adulthood
→ opportunity to interact with fellow rat is protective against addiction-like behaviors
2. Animal models fail to capture the unique capacity for language and long-term goals in humans
> capacity for language in humans is critical during treatment and efforts to reduce or abstain from drug use
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what are some critical notes on human research on drug habits?
- Limits to existing experimental models of habits in humans
- Challenge of interpreting self-report:
> while many people describe their drug compulsion as a habit, others report that their behavior is driven by craving rather than habits
- Alcohol/substance abuse can give rise to cognitive dissonance. This is experienced as an unpleasant tension due to conflict between one’s beliefs and conflicting behavior
> Cognitive dissonance can lead to post-hoc rationalizing of one’s behavior (e.g. in terms of craving )
> motivational rather than habitual account, which would be out of control
81
what are some other factors that lead drugs to become a compulsive habit instead of staying a goal-directed behavior?
- drugs are a potent reinforcer
- impaired cognitive control functions may increase reliance on habits
- stress and sleep deprivation have been shown to increase reliance on habits
→ more research is needed to understand the role of fundamental (psychological & neurobiological) processes - including habits - in addiction
82
what is the clinical relevance of habits?
→ what does this show?
- Addiction
> prolonged drug abuse leads to impaired goal-directed and inhibitory control
> more activity in the posterior putamen than in the prefrontal cortex
- OCD
> impaired in directing their responses towards still-valuable outcomes and away from devalued ones
> shock-avoidance paradigm
- Eating disorders
> obese individuals showed accellerated habit formation
→ this shows that habits may be a transdiagnostic trait for compulsive conditions
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what other disorders is habit propensity associatd to?
- Tourettes
- healthy ageing
- Parkinson's disease
- SAD
- schizophrenia
- (stress)
84
what is the shock-avoidance paradigm?
what were the results?
- mild shocks to left and right wrists could be avoided by pressing foot pedals on corresponding sides
- at the end of learning phase, electrodes were removed (removing the threat of shock)
= OCD patients continued to press devalued shock
→ related to hyperactivity in the ventromedial prefrontal-orbitofrontal cortex and caudate
85
How should habits be studied?
- integrative approach through disciplines
> e.g. social psychology, experimental psychology, behavioral neuroscience, ...
- experimental research + diary investigations + structured observations
86
what are some habit interventions?
- turn desired behavior into habit as fast as possible through repetition in stable context
- "implementation intention": IF i eat, THEN i brush my teeth
- create a window of opportunity by removing contextual cues that are associated with old, undesirable habits
- capitalize on extisting habits, which can act as R-R triggers (e.g. you have habit of brushing teeth, and you connect that to new habit of flossing)
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Knowledge Clip
Executive functions in addiction:
→ Why do drug addicts continue to use drugs or alcohol despite being aware of the disastrous consequences?
We already know that...
- drugs powerfully elicit craving/wanting
- drugs shift the balance from goal-directed towards habitual control (dual-process)
> here, we look at the top-down executive functions
88
What are the main executive functions? (x5)
- Error monitoring
> ability to detect erroneous responses
> EEG studies
- Working memory
> ability to maintain and manipulate information in memory
> e.g. self-ordered pointing task, digit span, ...
- Cognitive flexibility
> ability to shift attention between one task and another
> via set shifting (e.g. Winsconsin-card sorting test)
- Decision making
> basing choices on the advantages/costs/risks associated with behavior
> e.g. Iowa gambling task, Delay discounting task, ...
- Inhibitory (impulse) control
> ability to inhibit actions and thoughts
> e.g. Go/NoGo task, stop-signal task, Stroop task
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what brain areas are the executive functions associated to?
- Prefrontal Cortex
> e.g. working memory→ Dorsolateral PFC (dlPFC)
> e.g. decision making→ Medial orbitofrontal cortex (OFC) + ventromedial PFC (vmPFC) [overlapping brain regions]
(picture 23)
90
How can we study these brain areas?
- Structural Magnetic Resonance Imaging
- Study brain volume and structural alterations in addictio
> in grey matter (cell bodies) and white matter (myelinated axons)
91
How is the brain affected in people with an addiction?
- why is it important?
(picture 24)
! Brain volume diminishes
- gray matter volume reduction
> especially in PFC, cingulate cortex, insula
- frontal white matter is affected by substance abuse, and points to vulnerability factor
→ gray and white matter alterations partially predate substance use, but are also affected by it
→ these alterations may mediate cognitive dysfunctions
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Are reductions in gray matter a consequence of substance abuse or a risk factor?
- Consequence vs Risk factor: hard to tell!
→ PFC gray matter volume has been shown to decrease gradually in people with an alcohol and morphine addiction
> suggests that reduction is consequence
→ gray matter deficits are attentuated after a period of abstinence
> suggests that reduction is consequence
→ nonabusing individuals with family histories of substance abuse have gray matter reductions (e.g. amygdala)
> suggests that reduction is might be risk factor
93
What are the three main pathways of addiction?
1. mesolimbic dopamine pathway→ craving
2. nigrostriatal pathway→ habits
3. mesocortical pathway→ cognitive control functions
- can be studied through PET (positron emossion tomography)
- in addiction, these pathways are disrupted
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Cognitive Flexibility
- what is the Winsconsin Card Sorting Test (WCST)?
- how is this used in addiction research?
- participants are asked to match the cards, but not told how to match them
- they are given feedback regarding whether a particular match they made is right or wrong
! the card sorting rule is changed regularly and unannounced ("set shifting")
> e.g. sorting on the basis of colour, number, shape, ...
> the participant has to be mentally flexible and adapt to the new rule (change behavioral response in face of changing contingencies)
! perseverative errors indicate a lack of flexibility
! performance is impaired in individuals with a history of substance abuse
(picture 25)
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Decision making
- what is Delay Discounting?
- degree to which a rewars decreases in subjective value as a function of the time that one has to wait for it
- impulsive choice for smaller reward now vs larger reward later
(picture 26)
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how is Delay Discounting measured?
- what does the graph show?
- in children, through the marshmallow experiment
- in adults, with monetary compensations
(picture 27)
> the graph shows delayed reward discounting curves, of the subjective value of $100 delayed from one day to a year
> the greater the delay (the longer they have to wait), the lower the subjective value of the delayed reward
> Jan is less impulsive, because for him 62$ today = 100$ in 60 days
> Rick is more impulsive, because for him 14$ today = 100$ in 60 days
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Delay discount functions
- what does the graph show?
(picture 28)
- tolerance for delayed rewards, as opposed to reward now, is lower
→ discounting of delayed rewards has been observed in nearly all classes of substance abuse
98
Decision Making
- how does the Iowa gambling task work?
~ emphasis on weighting positive and negative consequences & dealing with uncertainty
~ mimic reality of everyday life situations
- participants have to choose cards from four decks on computer screen
- every time they choose a card they will win some money, and they are encouraged to win as much money as they can
- they have to discover which decks are advantageous on long run
> they are not given the rules, they have to discover them through trial and error
99
How do the decks work?
- two decks give immediate lower gains and low penalties (advantageous on long run)
- two other decks give higher gains but also high penalties (disadvantageous on long run)
! participants should learn to choose less immediate advantageous gains in order for overall better result
(picture 29)
100
what is the result of the Iowa gambling task?
- patients with mOFC/vmPFC dysfunction perseverate on the bad decks in the IGT compared to controls
- individuals with alcohol and substance addiction also perform relatively poorly on this task
- this was shown also in neuroimaging studies, where lower activation in vmPFC and dlPFC was found in addicts compared to controls
101
why are these findings on Decision Making clinically relevant?
- very relevant in treatment
> we must take into account the inability to delay immediate gratification, and we should focus on long-term goals
> it can be chosen to attach immediate positive consequences to the desired behavior
102
what is Contingency Management?
- type of behavioral therapy in which the participants are rewarded for postive behavioral changes
> e.g. monetary-based reinforcers are offered for submission of drug-negative urine sample
- rewards consists of vouchers to be used on retail goods/services or in the opportunity to win prizes
! there is a lot of empirical evidence behind efficiency of contingency management
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Inhibitory control
- what is it?
- how can it be measured?
- Ability to inhibit prepotent response
- it can be measured with:
> Go/NoGo task
> Stop-signal task
> Stroop task
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Go/NoGo task
- people should respond as quickly as they can on "go" signal
- they should also refrain from responding when "NoGo" signal
> failure to suppress responding to NoGo signal is interpreted in diminished inhibitory control
(picture 30)
105
Stop-Signal task (SST)
- cue to press certain key is occasionally followed by stop signal
- participants have to inhibit activated response
- the later the stop signal is presented (greater interval between cue and stop signal), the more difficult the trial
> ability to stop response that has already been initiated
(picture 31)
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What did studies on Go/NoGo task and Stop-signal task show?
- response inhibition is impaired in substance use disorders
- fMRI studies showed that the dorsolateral anterior cingulate cortex (dACC) is hypoactive during these inhibitory control tasks
> this was associated to impaired performance in addicted individuals
107
Stroop Task (inhibitory control)
- what does it show?
- Word meaning is in contrast with ink colour
- Slower performance and more errors during
incongruent trials are typical of PFC dysfunction
> ACC plays a role in conflict detection, and the dlPFC in conflict resolution (in this task) [neuroimaging studies]
> substance abuse associated with impaired performance
(picture 32)
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What is the role of impaired inhibitory control in addicts?
+ clinical relevance
- Impaired inhibitory control may contribute to the inability of addicted individuals to inhibit excessive drug taking
- Impaired response inhibition may also predispose individuals to addiction
- Clinical relevance: (potentially) inhibition training (but not a lot of research yet in this area)
109
what are the Neural Basis of executive dysfunction in addiction?
- executive control deficits in addiction are related to dysfunction in PFC, ACC, OFC
- less evidence for involvement of other brain regions
- variability across studies relate to cognitive test used, characteristics of the sample, duration and frequency of substance abuse, neuroimaging technique, type of substance used, ...
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Executive functions in addiction: Conclusions
- Substance abuse is marked by mild, yet pervasive, cognitive dysfunction
> These impairments may be a consequence of the neurotoxic effects of substances and alcohol, particularly on the prefrontal cortex
> ... But may also constitute vulnerability factors for the development of an addiction
→ Cognitive dysfunction may lead to a negative spiral in substance abuse
111
How are vulnerability factor and neurotoxic effects related to each other in substance abuse?
(picture 33)
- Vulnerability factor
> low cognitive control predicts future drug use, partly due to genetic bases
- Neurotoxic effects
> chronic use disrupts functioning of frontal and striatal networks involved in cognitive control
- acute effects of drugs on neural activity
> can cause impaired cognitive control
- chronic stress, sleep deprivation/disruption, ...
112
How are executive functions considered a double trouble?
(picture 34)
113
Conclusion of the knowledge clip
+ how is this relevant for the transdiagnostic perspective?
- (albeit as a risk factor or as a consequence of substance abuse) cognitive dysfunction is considered to accelerate the development of addiction, threaten abstinence, and increase attrition from treatment
- This is relevant for the transdiagnostic perspective: other mental disorders that are characterized by compulsive behaviour (in the broad sense), have also been linked with cognitive dysfunction
