Articles (Mundy, Waelti, Steinberg, McNally, Likhtik)
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Articles (Mundy, Waelti, Steinberg, McNally, Likhtik)

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Questions and Answers

What effect does a positive reward-prediction error (RPE) have on cue-reward associations?

  • It strengthens cue-reward associations. (correct)
  • It eliminates the need for rewards.
  • It weakens cue-reward associations.
  • It has no effect on cue-reward associations.

    • In the context of reinforcement learning, what happens when a reward is unexpectedly omitted?

  • A positive prediction error is generated.
  • A negative prediction error is produced. (correct)
  • Dopamine activity increases.
  • There is a significant increase in anticipatory responses.

    • Which visual stimuli elicited anticipatory licking in the test phase?

  • A and B
  • A and AX (correct)
  • B and Y
  • Only A

    • How does blocking relate to learning in reinforcement learning?

    <p>It prevents learning about new rewards when an existing predictor is present.</p> Signup and view all the answers

    What effect does a downshift in reward salience have in the extinction process?

    <p>It slows down the extinction process.</p> Signup and view all the answers

    Which method was employed to artificially mimic a reward-prediction error in the described study?

    <p>Optogenetics.</p> Signup and view all the answers

    In the results section, what was observed with dopamine responses to stimulus B?

    <p>There was no response to B during the test.</p> Signup and view all the answers

    What is the primary finding regarding the effects of microinjections of naloxone into the vlPAG during extinction training?

    <p>Naloxone impairs the extinction of Pavlovian fear conditioning.</p> Signup and view all the answers

    How does the dose of naloxone affect the freezing response in rats during extinction training, according to experiment #4?

    <p>Higher doses of naloxone increase freezing responses.</p> Signup and view all the answers

    Which experimental method was used to assess the impact of naloxone on the extinction of conditioned fear?

    <p>Microinjections into brain regions</p> Signup and view all the answers

    What was the outcome when naloxone was microinjected into the dPAG during fear conditioning?

    <p>It did not impair the extinction of Pavlovian fear conditioning.</p> Signup and view all the answers

    What hypothesis is suggested regarding the role of ITC neurons in fear extinction processes?

    <p>Disruption of ITC neurons would impair fear extinction.</p> Signup and view all the answers

    What does reduced firing of dopamine neurons in the VTA during a downshift in reward indicate?

    <p>Negative prediction error</p> Signup and view all the answers

    How do optogenetic manipulations of dopamine neurons affect extinction learning?

    <p>They impair the ability to extinguish learned behaviors</p> Signup and view all the answers

    What type of prediction error enhances the learning of an association during a non-rewarded trial?

    <p>Positive prediction error</p> Signup and view all the answers

    What role do phasic dopamine signals play in the learning process?

    <p>They influence learning from changes in reward expectations</p> Signup and view all the answers

    What happens to animals with inhibited dopamine neurons during both positive and negative reward prediction errors?

    <p>They exhibit significant learning deficits</p> Signup and view all the answers

    What outcome is observed when rats undergo extinction via nonreinforced presentations of the conditioned stimulus?

    <p>Reduction in freezing response</p> Signup and view all the answers

    What is the effect of naloxone injections in the vlPAG on fear extinction?

    <p>Impairment of fear extinction</p> Signup and view all the answers

    What was the primary goal of the first experiment regarding opioid receptors in the vlPAG?

    <p>To assess the impairment of extinction</p> Signup and view all the answers

    What variable parameter was adjusted in the second experiment involving CS exposures during extinction?

    <p>Duration of the CS presentations</p> Signup and view all the answers

    What is the primary focus of the role of opioid receptors in fear extinction according to the experiments conducted?

    <p>Influencing the acquisition and expression of fear extinction</p> Signup and view all the answers

    What happens to dopamine activity when a reward is unexpectedly omitted?

    <p>It decreases.</p> Signup and view all the answers

    Anticipatory licking was observed for stimulus B.

    <p>False</p> Signup and view all the answers

    What is the formula for calculating reward-prediction error (RPE)?

    <p>RPE = Actual Reward - Expected Reward</p> Signup and view all the answers

    A positive reward-prediction error strengthens cue-reward associations through the presentation of a(n) __________ reward.

    <p>unpredicted</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Reward-Prediction Error = Difference between actual and expected rewards Positive RPE = Strengthens cue-reward associations Negative RPE = Weakens cue-reward associations Extinction = Loss of learned behavior due to absence of reward</p> Signup and view all the answers

    During which phase did anticipatory licking occur for stimulus A?

    <p>Phase 1</p> Signup and view all the answers

    Dopamine neurons become more active when a reward is expected and presented.

    <p>True</p> Signup and view all the answers

    What is the main role of dopamine activity in the learning process?

    <p>Dopamine activity acts as a teaching signal, influencing learning about antecedent cues.</p> Signup and view all the answers

    What type of prediction error is critical for extinction learning?

    <p>Negative prediction error</p> Signup and view all the answers

    Optogenetic activation of dopamine neurons during a non-rewarded trial enhances the extinction of learned behaviors.

    <p>False</p> Signup and view all the answers

    What is the effect of opioid receptor manipulation in the vlPAG on fear extinction?

    <p>Impairment of fear extinction</p> Signup and view all the answers

    Dopamine neuron activity during unexpected __________ omission was necessary for adjusting behavior in response to reduced rewards.

    <p>reward</p> Signup and view all the answers

    Match the type of prediction error with its effect on learning:

    <p>Positive prediction error = Enhances association learning Negative prediction error = Important for extinction learning Dopamine inhibition = Leads to learning deficits Dopamine activation = Facilitates reward expectations</p> Signup and view all the answers

    Which result was observed when dopamine neurons were inhibited during reward prediction errors?

    <p>Significant deficits in learning</p> Signup and view all the answers

    Animals with optogenetic stimulation during a downshift in reward experience enhanced extinction learning.

    <p>False</p> Signup and view all the answers

    What were the rats subjected to in the fear acquisition experiment?

    <p>Auditory conditioned stimulus paired with foot shock</p> Signup and view all the answers

    What is the primary finding regarding the Hippocampus and Perirhinal Cortex in perceptual learning?

    <p>The Hippocampus selects for scene learning while the Perirhinal Cortex focuses on face learning.</p> Signup and view all the answers

    Participants with bilateral MTL damage show no disruption in discriminating pre-exposed from non-exposed faces.

    <p>False</p> Signup and view all the answers

    What regions of the brain are investigated in terms of visual information encoding?

    <p>Hippocampus and Perirhinal Cortex</p> Signup and view all the answers

    The functional region of interest for face encoding is known as the ______.

    <p>FFA</p> Signup and view all the answers

    In Experiment 2A, what was noted about discrimination accuracy between stimulus types?

    <p>There were no differences in discrimination accuracy.</p> Signup and view all the answers

    Match the following Hippocampus regions with their functions:

    <p>Anterior Hippocampus = No association with discrimination accuracy Posterior Hippocampus = Discrimination accuracy for scenes Perirhinal Cortex = Discrimination accuracy for faces</p> Signup and view all the answers

    What was the control group's performance trend across the blocks in terms of discrimination?

    <p>Improved performance across blocks for each stimulus type.</p> Signup and view all the answers

    Greater BOLD activity was observed for non-exposed face pairs in the FFA region.

    <p>False</p> Signup and view all the answers

    What was the primary outcome of microinjections of naloxone into the vlPAG during extinction training?

    <p>Impairment of extinction of conditioned fear</p> Signup and view all the answers

    Microinjections of naloxone into the dPAG impair the extinction of conditioned fear.

    <p>False</p> Signup and view all the answers

    During which phase did naloxone animals show significantly more freezing than saline animals?

    <p>First 4 minutes of the CS on day 1 of extinction</p> Signup and view all the answers

    The effects of naloxone on fear extinction were __________, indicating a relationship between dose and freezing response.

    <p>dose-dependent</p> Signup and view all the answers

    Match the experiments with their findings:

    <p>Experiment #1 = Impairment of extinction but no reinstatement Experiment #2 = Impairment manifest during drug-free test Experiment #3 = No impairment in extinction Experiment #4 = Dose-dependent effects of naloxone</p> Signup and view all the answers

    What effect does a higher dose of naloxone have on freezing during a drug-free test?

    <p>Increases freezing response</p> Signup and view all the answers

    Disruption of the ITC neurons is hypothesized to promote fear extinction.

    <p>False</p> Signup and view all the answers

    Which areas of the brain are involved in fear expression and inhibition?

    <p>BLA, CeA, ITC</p> Signup and view all the answers

    Study Notes

    ### Dopamine Signals and Reward Prediction Errors

    • Dopamine signals are consistent with reward prediction errors in temporal difference reinforcement learning.
    • Dopamine activity increases during unexpected rewards (positive prediction error), decreases during omitted rewards (negative prediction error), and remains unchanged during expected rewards (no prediction error).
    • Monkey study: Monkeys were trained to associate visual stimuli (A, B, X, Y) with rewards.
      • Phase 1: A reliably predicted reward.
      • Phase 2: B never predicted reward.
      • Phase 3: AX combination predicted reward (learning about compound cues).
      • Phase 4: BY combination predicted reward.
    • Dopamine activity in the study:
      • Increased in response to A and AX but not to X because it was not directly paired with reward.
      • Increased in response to BY and Y because they were paired with reward.
      • Decrease in response to A when the expected reward was omitted.
    • Optogenetics: Artificial manipulation of dopamine neurons to mimic reward prediction errors.
      • Optogenetic inhibition: Blocking of dopamine neurons during downshift extinction (less reward than expected) impaired extinction learning.
      • Optogenetic activation: Mimicking a positive prediction error during non-rewarded trials enhanced learning of an association with reward.
      • Conclusion: Dopamine signals are causally linked to learning, with changes in their activity affecting learning from changes in reward expectations.

    Opioid Receptors and Fear Extinction

    • Hypothesis: Opioid receptor antagonism in the periaqueductal gray (PAG) impairs fear extinction.
    • Methods: Rats were trained to associate an auditory stimulus (CS) with a foot shock (US), leading to fear conditioning.
    • Fear extinction: Extinction training involved repeated presentations of the CS without the US, aiming to reduce the freezing response.
    • Naloxone: An opioid receptor antagonist, its effects were tested on different PAG subregions.
    • Experiment #1: Microinjections of naloxone into the ventrolateral PAG (vlPAG) impaired fear extinction during the initial phase but did not reinstate the extinguished fear response.
    • Experiment #2: Naloxone in the vlPAG also impaired extinction, confirming the reliability of the impairment and demonstrating its effect on a drug-free test.
    • Experiment #3: Naloxone microinjections into the dorsolateral PAG (dlPAG) did not impair fear extinction.
    • Experiment #4: Naloxone's effect on fear extinction was dose-dependent, with higher doses leading to greater freezing during testing.
    • Conclusion: Opioid receptors in the vlPAG are crucial for fear extinction. Disrupting them impairs the ability to extinguish conditioned fear responses.

    Interconnected Brain Regions and Fear Extinction

    • Fear conditioning: The amygdala (BLA) plays a critical role in fear conditioning, with projections to the central amygdala (CeA) leading to fear expression.
    • Fear extinction: The infralimbic cortex (ITC) inhibits fear expression by projecting to the CeA.
    • ITC disruption: Disrupting ITC neurons is hypothesized to impair fear extinction, leading to the persistence of fear responses after extinction training.

    Mundy et al. Study

    • Hypothesis: Hippocampus and Perirhinal Cortex contribute to distinct types of perceptual learning.
      • Hippocampus plays a selective role in scene learning.
      • Perirhinal Cortex plays a dominant role in face learning.
    • Participants:
      • Two patients with brain damage (HC3, MTL3).
      • 16 healthy participants.
    • Methods:
      • Combined causal (lesioned patients) and correlational (fMRI) approaches to study MTL's role in visual information encoding.
      • fMRI with BOLD signal measured brain activity.
      • Focused on regions of interest (fROI):
        • FFA: Face encoding region.
        • PPA: Scene encoding region.
        • MTL regions: Perirhinal Cortex (PrC), Anterior Hippocampus (AntHC), Posterior Hippocampus (PostHC).
    • Results:
      • Experiment 1 (Lesion Study):
        • Discrimination:
          • Control participants showed equal differentiation between pre-exposed and non-exposed stimuli.
          • HC3 exhibited difficulty differentiating pre-exposed and non-exposed scenes.
          • MTL3 displayed impairment in differentiating both pre-exposed faces and scenes.
        • Reaction Time (RT):
          • Control participants showed no RT differences between pre-exposed and non-exposed stimuli.
          • HC3 took longer to respond to scene stimuli.
          • MTL3 took longer to respond to face and scene stimuli.
        • Learning:
          • Control participants showed learning across blocks for all stimulus types.
          • HC3 showed learning for dots and faces but not scenes.
          • MTL3 showed learning for dots but not faces or scenes.
      • Experiment 2 (fMRI Study):
        • 2A (Exposure History):
          • No significant differences in discrimination accuracy between stimulus types.
          • Participants performed better in discriminating pre-exposed stimuli compared to non-exposed stimuli.
        • 2B (Discrimination Accuracy):
          • FFA exhibited higher activity for pre-exposed face pairs compared to non-exposed face pairs.
          • PPA showed higher activity for pre-exposed scene pairs compared to non-exposed scene pairs.
          • No modulation observed for dots.
          • PrC showed association with discrimination accuracy for faces but not scenes.
          • PostHC showed association with discrimination accuracy for scenes but not faces.
          • AntHC exhibited no association with discrimination accuracy for either faces or scenes.

    Waelti et al. Study

    • Hypothesis: Dopamine signals are not always consistent with reward prediction errors.
      • Emphasizes the prediction error signal in temporal difference reinforcement learning.
    • Participants: Monkeys.
    • Methods:
      • Four visual stimuli (A, B, X, Y) presented during four phases.
        • Phase 1: A + juice (A > CR)
        • Phase 2: B + no juice (B)
        • Phase 3: AX + juice (A+X > CR)
        • Phase 4: BY + juice (Y > CR)
    • Results:
      • Anticipatory Licking:
        • Present for A and AX but absent for X during the test phase.
        • No anticipatory licking observed for B.
        • Anticipatory licking for BY (since it was paired with juice).
        • Anticipatory licking for Y during the test phase.
      • Dopamine Activity:
        • Phase 1 & 2:
          • A: Dopamine response to CS, dopamine dip when reward not presented.
          • B: No response to CS, dopamine activity to unexpected reward.
        • Compound Phases:
          • AX: Dopamine response to A+X.
          • BY: Increasing dopamine response to B+Y.
        • Test Phase:
          • X: Response to CS (but less than Y), no change in response when not presented.
          • Y: Increased response to CS, dopamine dip when not presented.
      • Reward Prediction Errors:
        • Unexpected rewards: Prediction error signal; increase in dopamine activity.
        • Omitted reward: Negative prediction error; decrease in dopamine activity.
        • Expected reward: No prediction error; no change in dopamine activity.

    Steinberg et al. Study

    • Hypothesis: Dopamine activity functions as a teaching signal, influencing learning about antecedent cues.
      • Focuses on the role of reward prediction errors (RPE) in learning.
    • Methods:
      • Used optogenetics to artificially mimic RPE by stimulating dopamine neurons.
      • Conducted behavioral experiments focusing on blocking and extinction tasks.
    • Results:
      • Downshift Extinction Task:
        • Dopamine neurons exhibited reduced firing in response to a downshift in reward, indicating a negative prediction error.
        • Optogenetic inhibition of dopamine neurons during downshift impaired extinction of learned behavior.
      • Non-rewarded Trial:
        • Optogenetic activation of dopamine neurons during non-rewarded trials enhanced learning of a stimulus-reward association.
      • Phasic Dopamine Signals:
        • Phasic dopamine signals directly influence learning, with manipulation (inhibition or activation) affecting the ability to learn from reward expectation changes.
      • Unexpected Reward Omission:
        • Dopamine neuron activity during unexpected reward omission was crucial for behavioral adjustments in response to reduced rewards.
      • Dopamine Neuron Inhibition:
        • Animals with inhibited dopamine neurons during reward prediction errors (positive and negative) showed learning deficits in response to changing reward contingences.

    McNally et al. Study

    • Hypothesis: Opioid receptors within the Periaqueductal Gray (PAG) play a crucial role in fear extinction, specifically through conditioned freezing behavior.
    • Methods:
      • Fear Acquisition: Rats were conditioned to associate an auditory CS with a foot shock US (tone + footshock = freezing).
      • Fear Extinction: Extinction involved repeatedly presenting the CS without the US (tone + no footshock = decreased freezing).
      • Experiments:
        • Experiment 1: Focused on the role of vlPAG opioid receptors in acquisition and expression of fear extinction, using microinjections of the opioid receptor antagonist naloxone.
        • Experiment 2: Further examined the role of vlPAG opioid receptors in extinction, using different CS exposure parameters and a drug-free test.
        • Experiment 3: Investigated the role of dPAG opioid receptors in extinction, using the same methodology as Experiment 1.
        • Experiment 4: Examined the dose-response relationship between naloxone and fear extinction in vlPAG.
    • Results:
      • Experiment 1:
        • Naloxone microinjections into vlPAG impaired fear extinction but did not reinstate fear responses.
        • Naloxone microinjections into PAG disrupted the development but not the expression of extinction.
      • Experiment 2:
        • Naloxone microinjections into vlPAG hindered fear extinction and this impairment was observed in a drug-free test.
      • Experiment 3:
        • Naloxone microinjections into dPAG did not impair fear extinction, highlighting the specific role of the vlPAG in this process.
      • Experiment 4:
        • The effects of naloxone on fear extinction exhibited a dose-dependent relationship- as the naloxone dose increased, so did the amount of freezing observed.

    Likthik et al. Study

    • Hypothesis: Disrupting the Interpeduncular Nucleus (ITC) neurons will impair fear extinction expression, leading to persistent fear responses even after extinction training.
    • Key Findings:
      • Fear Conditioning: The basolateral amygdala (BLA) projects to the central amygdala (CeA), leading to fear expression.
      • Fear Extinction: The BLA projects to the ITC, which then inhibits the CeA, suppressing fear expression.
      • ITC Neuron Disruption: Impaired fear extinction due to persistent fear responses.

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    Explore how dopamine signals correlate with reward prediction errors through a study on monkeys and their learning of visual stimuli. This quiz delves into different phases of the study and the relationship between dopamine activity and expected or unexpected rewards.

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