Learning about the world Flashcards

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1
Q

What is the main neurotransmitter involved in reward learning (reward-motivated behaviour)?

A

Dopamine

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2
Q

What characterises the dopamine activity in a schizophrenic person?

A

Aberrant dopamine activity

  • higher D2 receptor density -> higher levels of dopamine
  • L-Dopa taken up quicker -> higher production of dopamine
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3
Q

What have molecular imaging suites shown on the association between dopamine activity and psychotic symptoms?

A

Degree of sensitisation of mesostriatal dopamine system is associated to severity of psychotic symptoms

  • > amphetamines and cocaine increase dopamine and worsen symptoms in schizophrenic patients
  • > D2 receptor antagonists improve psychotic symptoms
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4
Q

To which neurotransmitter pathway are the negative symptoms of psychosis associated?

A

Mesocortical pathway

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5
Q

To which neurotransmitter pathway are the positive symptoms of psychosis associated?

A

Mesolimbic

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6
Q

What is the aim of the treatment of negative symptoms in schizophrenia?

A

Increase dopamine neurotransmission

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7
Q

What is the aim of the treatment of positive symptoms in schizophrenia?

A

Slow down dopamine neurotransmission

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8
Q

What are prediction errors?

A

Dopamine-dependent signal that play a role in learning

  • mesolimbic dopaminergic regions
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9
Q

What is the dopaminergic response when there is no prediction of a reward and a reward occurs (Schultz, 1971)?

A
  • Surprise = salient event -> increase in firing when reward is given
  • Response variation to unpredicted primary rewards
  • > the nice the reward, the higher the signal
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10
Q

What is the dopaminergic response when a reward is predicted and a reward occurs (Schultz, 1971)?

A
  • Dopamine increase at presentation of conditioned stimulus
    = recognition that reward will come
  • Dopamine signal shifts in time from reward to predictive stimulus = prediction learning
  • When reward given as expected, there’s no increase in dopamine release
  • > no prediction error
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11
Q

What is the dopaminergic response when a reward is predicted but no reward is given (Schultz, 1971)?

A

Dopamine release decreases to below normal levels

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12
Q

What is the reward prediction learning effect in the study of Schultz (1967)?

A

Dopamine signal shifts in time from reward to prediction stimulus

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13
Q

What is the effect of expectation and learning on dopamine release?

A

As learning occurs, dopamine firing adjusts

  • when subject geins to expect certain outcome from certain scenario, prediction error becomes smaller and smaller
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14
Q

What is the consequence of the aberrant dopamine activity in schizophrenic patients as explained by Kapur (2003, 2004)?

A

Aberrant salience and positive symptoms

  1. Dysregulated firing and/or release of dopamine
  2. Aberrant sense of novelty and abnormal assignment of salience to stimulant internal representations
    - > stimulus that may not be meaningful evokes dopamine firing
  3. Delusions as negative cognitive schema the patient develops to explain aberrant salience
    - > an inference is required to account for salient/odd experiences that will be interpreted in meaningful way (e.g. sense of persecution)

-> they shape perception and interpretation of new information

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15
Q

When are psychotic patients treated according to Kapur (2003, 2004)?

A

When the aberrant salience assigned to stimuli and internal representations impacts on behaviour or causes distress

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16
Q

What is the effect of antipsychotics according to Kapur (2003, 2004)?

A
  • Block effects of dopamine and dampen the salience of preoccupying symptoms
  • May also dampen the motivational salience of normal events
17
Q

What are the reward-related areas of the brain?

A
  • Mesocortical pathway
  • Mesolimbic pathway
  • Nigrostriatal pathway
  • Prefrontal cortex
  • Nucleus accumbens
  • Striatum
  • Ventral tegmental area
  • Substantia nigra
18
Q

What did the study of Murray and colleagues (2008) on salience and (first episode) psychosis show?

A
  • Instrumental learning task involving monetary gains to increase motivation
  • Patients and controls learned to choose the high probability stimulus on reward trials (no significant differences)
  • Reinforcement-related speeding: both patients and controls were significantly faster on reward trials than neutral trials
  • BUT, patients were significantly faster than controls on neutral trials
  • > psychotic patients found the neutral trials inappropriately motivationally significant
  • More positive symptoms were associated with lower distinction between salient and non-salient events in the brain (observed in substantia nigra and VTA)
19
Q

Which model of psychosis does the study of Murray and colleagues (2008) support?

A

Model of psychosis that postulated abnormal dopamine-dependent motivational salience as key mechanism of symptoms

20
Q

Which cause was attributed to the reinforcement-related speeding observed in the study of Murray and colleagues (2008)?

A

Anticipation of potential reward on reward trials

  • > enhanced motivation
  • > faster responding
21
Q

What did the study of Corlett and colleagues (2007) show?

A
  • Brain activation in controls was greater for salient than for non-salient events (as in Murray’s study)
  • effect attenuated and/or partially reversed in patients
  • Higher delusions were associated with the brain response only in prefrontal regions, not midbrain
22
Q

How can learning occur in psychotic patients if their brain system is not functioning normally (Murray, Corlett and Fletcher, 2010)?

A
  • Standard brain activation patterns may be present in psychosis but partially obscured by grater noise
  • Brain signals may be more sensitive to real group differences than behavioural measures
  • Patients may achieve comparable levels of performance to control subjects by employing alternative or compensatory neural strategies outside areas of interest
  • Could be due to nature of task -> differences may become visible once task demands increase
23
Q

What is anhedonia?

A

‘Markedly diminished interest or pleasure in all, or almost all, activities most of the day, nearly every day’

24
Q

What is avolition?

A

“Poverty of will” and disabling restriction in the initiation of activity, including goal-directed behaviour

25
Q

What are the suggested to key negative symptoms in schizophrenia?

A
  • Anhedonia

- Avolition

26
Q

What characterises negative symptoms in schizophrenia?

A
  • Associated with reduced real-world functioning
  • Poorly understood
  • May worsen under antipsychotic treatment
  • Hypothesis on aetiology: hypodopaminergic state specifically in prefrontal areas
  • Research supports role of striatal reward mechanisms
27
Q

What does the large body of behavioural research suggest on the capacity of patients with schizophrenia to experience pleasure?

A

Intact “hedonic experience”

  • majority of studies show people with schizophrenia liking or enjoying positive things
28
Q

What is the hypothesis of researchers that showed people with schizophrenia have an intact “hedonic experience”?

A

Clinical measures used to assess anhedonia may not reflect consummatory (in the moment) pleasure BUT rather focus on ability to anticipate pleasure

  • may explain why normal experiences of pleasure do not translate to motivational (goal-directed behaviour)
  • > potential lack of anticipation of enjoyable effect of stimuli in schizophrenia
29
Q

Which tasks investigate reward anticipation?

A
  • Learning task used by Graham Murray and colleagues (2008)

- Monetary incentive delay task

30
Q

What did the monetary incentive delay task used by Jackal and colleagues (2006) show?

A

Visual cues predicted that a rapid response to a subsequent target stimulus would result either in monetary gain or loss, or would have no consequence

31
Q

What do neuroimaging studies show on reward anticipation in patients with schizophrenia patients?

A

Abnormalities in processes related to anticipation of reward

  • reduced ventral striatal activation during presentation of reward-indicating cues
  • > inversely correlated with severity of negative symptoms
  • similar patterns of reduced activation in ventral striatum in patients on typical mediation, but no atypical medication
32
Q

What could explain why patterns of reduced activation in the ventral striatum are observed in schizophrenic patients on typical medication but not atypical medication?

A
  • Atypical antipsychotics may normalise the reward response

- Or medication given to patients groups are fundamentally different

33
Q

What does value computation in anticipatory pleasure refer to?

A

Value of reward or desirable outcome

  • how much effort or “work” it will take to get that reward or outcome
34
Q

Why is it important to integrate value computations alongside anticipatory pleasure?

A

Drives the ability to generate and execute action plans necessary to achieve valued outcomes

35
Q

Which brain areas are implicated in the integration of value computations to anticipatory pleasure?

A

Frontal brain areas closely linked to striatal regions

  • dorsolateral prefrontal cortex
  • orbitofrontal cortex
  • anterior cingulate cortex
36
Q

What does the research evidence suggest on the reward value in schizophrenia (Bring and Barch, 2014?

A

Impairments in generating, maintaining and updating mental representations of value
- partly due to other cognitive problems (memory)

Aberrant value-effort computations: less effort for guaranteed monetary rewards in patients with negative symptoms vs controls