Fear Learning and Extinction
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Questions and Answers

What is the primary role of the thalamus in the fear learning process?

  • Transmits sensory information to the amygdala (correct)
  • Regulates emotional responses
  • Inhibits fear responses
  • Facilitates memory recall

    • How do lesions in the sensory thalamic nuclei affect fear learning?

  • Impair the ability to acquire fear conditioning (correct)
  • No effect on conditioning
  • Enhance fear acquisition
  • Facilitate fear extinction

    • What is the function of intercalated cells in the context of fear responses?

  • Regulate blood flow during fear responses
  • Enhance sensory processing
  • Promote aggressive behaviors
  • Inhibit neuronal firing in the amygdala (correct)

    • Which role does the hippocampus play in fear learning?

    <p>Aids in contextual fear learning</p> Signup and view all the answers

    Which statement is true regarding the pathways of fear learning?

    <p>There are both direct and indirect pathways to the amygdala from sensory inputs</p> Signup and view all the answers

    What effect does disrupting sensory information flow have on fear extinction?

    <p>Makes it harder to learn that a stimulus is no longer predictive of danger</p> Signup and view all the answers

    Which defense behavior is suggested to depend on the predatory imminence gradient?

    <p>Conditioned freezing</p> Signup and view all the answers

    What is the primary role of the infralimbic cortex in fear regulation?

    <p>Mediates fear extinction.</p> Signup and view all the answers

    What effect do lesions in the amygdala have on fear learning?

    <p>No learning of conditioned stimuli.</p> Signup and view all the answers

    How do intercalated cells function in the context of fear responses?

    <p>They modulate the expression of fear responses.</p> Signup and view all the answers

    What role does the hippocampus play in contextual fear learning?

    <p>It is crucial for distinguishing between contexts during extinction.</p> Signup and view all the answers

    Which of the following accurately describes the paths of fear learning processes?

    <p>The association between CS and US is processed by the central nucleus of the amygdala.</p> Signup and view all the answers

    What role does the infralimbic cortex (IL) play in fear processes?

    <p>Inhibits amygdala activity and promotes suppression of conditioned fear responses</p> Signup and view all the answers

    How do lesions in the prelimbic cortex (PL) affect fear responses?

    <p>Prevents the expression of conditioned fear responses</p> Signup and view all the answers

    What is the function of intercalated cells (ITC) within the amygdala?

    <p>Acts as gatekeepers that inhibit the expression of fear responses</p> Signup and view all the answers

    What impact do lesions of the hippocampus have on fear responses?

    <p>They impair contextual fear conditioning and extinction</p> Signup and view all the answers

    Which pathway allows for faster fear learning with less information being processed?

    <p>Direct pathway from the thalamus to the amygdala</p> Signup and view all the answers

    What is one consequence of lesions in the basolateral amygdala (BLA)?

    <p>Impairs emotional memory processing related to fear</p> Signup and view all the answers

    What effect do lesions of the ventrolateral PAG (vlPAG) have on fear responses?

    <p>Results in the failure to reduce fear responses even with repeated exposure</p> Signup and view all the answers

    How does the hippocampus contribute to the modulation of fear extinction?

    <p>By processing contextual information and emotional states</p> Signup and view all the answers

    What happens to fear responses when activity of the infralimbic cortex (IL) increases?

    <p>Fear responses are suppressed due to inhibition of the CeA</p> Signup and view all the answers

    What distinguishes the indirect pathway to the amygdala from the direct pathway?

    <p>It carries more information</p> Signup and view all the answers

    Which of the following behaviours is NOT a part of the fear response system?

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

    The perirhinal cortex is primarily involved in auditory information processing.

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

    What is the role of the thalamus in fear learning?

    <p>It acts as a sensory relay center that transmits sensory information to the amygdala.</p> Signup and view all the answers

    Conditioned freezing is characterized by behaviors such as ________ and a crouched posture.

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

    Match the brain area with its function in fear learning:

    <p>Thalamus = Sensory information relay to the amygdala Amygdala = Processing of fear responses Hippocampus = Contextual fear memory Perirhinal Cortex = Object recognition and visual processing</p> Signup and view all the answers

    What is the role of the central nucleus of the amygdala in fear conditioning?

    <p>It orchestrates conditioned responses.</p> Signup and view all the answers

    Neural circuits involved in fear extinction are solely located in the hippocampus.

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

    What happens to fear neurons during the first day of extinction?

    <p>Fear neurons show response to the tone.</p> Signup and view all the answers

    The hippocampus is crucial for ________ of fear after extinction learning.

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

    Match the following terms with their definitions:

    <p>Fear Acquisition = Learning to associate a stimulus with a fearful event Fear Extinction = Reduction in the conditioned response over time Spontaneous Recovery = Re-emergence of fear response after a delay Renewal = Reappearance of fear response in a different context</p> Signup and view all the answers

    What phenomenon occurs when a footshock is given without the conditioned stimulus?

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

    The basal amygdala is responsible for encoding fear acquisition only.

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

    During full extinction on Day 3, what occurs with fear neurons?

    <p>Fear neurons do not show responses.</p> Signup and view all the answers

    What role does the lateral amygdala (LA) play in fear learning?

    <p>It helps with encoding the CS-US association.</p> Signup and view all the answers

    The central amygdala (CeA) is responsible for suppressing fear responses.

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

    Which brain region is crucial for facilitating fear expression during fear conditioning?

    <p>Prelimbic cortex (PL)</p> Signup and view all the answers

    Lesions of the _____ prevent animals from being able to suppress conditioned fear responses.

    <p>infralimbic cortex</p> Signup and view all the answers

    Match the following brain structures with their roles in fear response:

    <p>Amygdala = Central to fear learning and emotional memories Hippocampus = Contextual fear learning Prefrontal Cortex = Modulates fear responses PAG = Mediates physiological fear responses</p> Signup and view all the answers

    Which of the following best describes the role of the basolateral amygdala (BLA)?

    <p>Integrates inputs and modulates emotional responses</p> Signup and view all the answers

    The thalamus sends information directly to the amygdala as part of the indirect pathway.

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

    What is the primary function of the intercalated cells (ITC) in the amygdala?

    <p>Control the flow of fear response information</p> Signup and view all the answers

    The _____ is involved in fear extinction by integrating emotional and contextual information.

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

    Match the following lesion effects with their consequences:

    <p>Lesion of LA = Impairment in fear learning Lesion of BLA = Difficulty in modulating emotional responses Lesion of CeA = Disruption in expressing fear responses Lesion of IL = Prevention of fear extinction</p> Signup and view all the answers

    What is one consequence of lesions in the ventrolateral PAG (vlPAG)?

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

    Fear responses can be expressed without a corresponding fear memory.

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

    Which pathway allows for slower, but more refined learning of fear responses?

    <p>Indirect pathway</p> Signup and view all the answers

    The _____ cortex facilitates fear expression by maintaining amygdala activity during fear conditioning.

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

    Study Notes

    Fear Learning

    • Assessment of Fear Conditioning:
      • Habituation: Absence of stimulation
      • Conditioning: Conditioned Stimulus (CS) paired with Unconditioned Stimulus (US), leading to Unconditioned Response (UR)
      • Testing: CS presented, eliciting Conditioned Response (CR)
    • Conditioned Freezing: Immobility, crouched posture with arched spine.
      • Footshock: Few trials needed for CS-US association
      • Rescorla-Wagner Model: Corresponds to the beta value (salience)
    • Fear as a Defensive System:
      • Orchestrates adaptive behaviours for protection.
      • Species-specific Defence Responses: Freezing, flight, fight, analgesia, autonomic arousal
      • Predatory Imminence Gradient: Determines which behaviour is expressed based on perceived threat level.

    Neurobiology of Fear Learning

    • Brain Areas:
      • Thalamus: Sensory relay center, transmitting sensory information (auditory, visual, somatosensory) to the amygdala.
        • Medial Geniculate Nucleus (MGN): Sends auditory information.
        • Direct and Indirect Pathways to the Amygdala:
          • Direct: Thalamus directly to amygdala.
          • Indirect: Thalamus to prefrontal cortex to amygdala.
    • Lesion Effects:
      • Fear Learning: Lesions in sensory thalamic nuclei impair fear conditioning.
        • Disruption of sensory inputs essential for CS-US association.
      • Fear Extinction: Disrupting sensory flow to amygdala hampers learning that the stimulus is no longer predictive of danger.

    Perirhinal Cortex

    • Role: Object recognition, visual information processing, integrates complex sensory information.
    • Interaction: With amygdala and hippocampus to modulate fear responses.
    • Outputs:
      • Projects to basolateral amygdala (BLA), providing detailed sensory input.
        • Aids in associating complex stimuli (CS) with aversive outcomes (US).
      • Projects to hippocampus, processing information about the context of fear learning and extinction.
        • Distinguishes between threatening and non-threatening contexts.
      • Projects to amygdala, refining fear response extinction when the stimulus no longer predicts danger.
    • Lesion Effects:
      • Fear Learning: Impairs forming detailed associations between specific objects or stimuli and aversive events.
      • Fear Extinction: Interferes with extinction learning, failing to update fear responses appropriately when the CS no longer predicts a threat.

    Amygdala

    • Central to fear learning: Processes and stores emotional memories, particularly fear-related stimuli.
    • Lateral Amygdala (LA): Receives sensory inputs related to CS and US from the thalamus and sensory cortex.
      • Encodes the CS-US association.
    • Basolateral Amygdala (BLA): Integrates inputs from LA and other brain regions (hippocampus and prefrontal cortex).
      • Modulates emotional responses.
    • Central Amygdala (CeA): Sends outputs to the hypothalamus and brainstem to trigger fear responses (e.g., increased heart rate, freezing).
      • Projects to regions responsible for autonomic and behavioral fear responses:
        • Periaqueductal Gray (PAG): Freezing.
        • Hypothalamus: Hormonal stress responses.
    • Lesion Effects:
      • LA or BLA Lesions: Impair acquisition and expression of fear learning.
      • CeA Lesions: Disrupt expression of fear responses (e.g., freezing), but not necessarily the acquisition of fear memories.

    Prefrontal Cortex (PFC)

    • Inputs: Amygdala, hippocampus, and thalamus.
      • Integrates information about emotional states, context, and sensory inputs.
    • Outputs:
      • Projects to the amygdala (BLA and intercalated cells (ITC)), modulating fear responses.
      • Connects to the hypothalamus and PAG, controlling physiological and behavioral fear responses.
    • Infralimbic Cortex (IL/IF) and Prelimbic Cortex (PL): Key role in fear regulation and fear extinction.
      • IL: Crucial for fear extinction.
        • Inhibits amygdala activity and suppresses conditioned fear responses.
      • PL: Facilitates fear expression by maintaining amygdala activity during fear conditioning.
    • Lesion Effects:
      • IL/IF Lesions: Prevent fear extinction.
      • PL Lesions: Impair conditioned fear expression.

    Intercalated Cells (ITC)

    • Gatekeepers: Control information flow within the amygdala (CeA).
    • GABAergic neurons: Inhibit other neurons, reducing fear expression.
    • Fear Extinction: IL/IF activity increases, stimulating ITCs, inhibiting CeA, and suppressing the fear response.
    • Fear Expression: PL and BLA activity reduce ITCs, disinhibiting CeA and expressing fear.

    Hippocampus

    • Contextual Fear Learning: Helps modulate fear extinction by providing information about the context of fear memory acquisition.
      • Distinguishes between contexts where fear is appropriate or not.
    • Inputs: Receives sensory, contextual information from cortical areas and amygdala.
    • Outputs: Projects back to amygdala (BLA) and PFC, regulating appropriate fear responses in context.
    • Lesion Effects:
      • Impair contextual fear conditioning: Difficulty associating fear responses with specific contexts.
      • Disrupt contextual fear extinction: Fail to differentiate between fear-inducing and non-fear-inducing environments.

    Periaqueductal Gray (PAG)

    • Involvement: Mediates behavioral and physiological fear responses (e.g., freezing, autonomic changes).
      • Ventrolateral PAG (vlPAG): Fear extinction.
      • Dorsal PAG (dPAG): Fear expression.
    • Inputs: Amygdala (CeA), hypothalamus, and PFC.
    • Outputs: Brainstem and spinal cord, controlling defensive behaviors (freezing, fight-or-flight) and autonomic regulation.
    • Lesion Effects:
      • vlPAG Lesions: Impair fear extinction.
      • dPAG Lesions: Can reduce fear response expression (freezing) but may not impair learning of fear.

    Pathways

    • Direct Pathway: Thalamus to Amygdala.
      • Fast learning but carries less information.
    • Indirect Pathway: Thalamus to PFC to Amygdala.
      • Slower learning but more refined.

    Discrete Neutral Stimuli in Fear Conditioning

    • Aim: Determine if sensory information about the CS travels via a direct thalamic-amygdalar pathway or a thalamocortical pathway.
    • Method: Disconnection lesions.
      • Lesion auditory thalamus in one hemisphere.
      • Lesion medial portion of MG.
      • Lesion A1.
      • Lesion in MGm and MGv.
    • Brain Areas:
      • MG - medial geniculate nucleus.
      • PIN – posterior intralaminar nucleus.
      • SG – suprageniculate nucleus.
      • MGm, PIN, SG project directly to amygdala.
      • MGv projects to auditory cortex.
    • Results: All groups except for full lesion (MGm & AUx) show high arterial pressure.
      • Minimal sympathetic nervous system activation for full lesion.
      • Both pathways are sufficient for learning.
      • Neither pathway is necessary.

    Tone and Context Processing

    • Non-legioned:
      • Explicit CS: Freezing on the second day, but not to context.
      • Explicit CS + Context: Freezing on the third day.
    • Amygdala legion: No learning to CS.
    • Cortex lesion:
      • Hippocampus:
        • Learn freezing to CS.
        • Cannot learn about context.

    Amygdala and Fear Responses

    • When CS-US associations are formed, conditioned responses are orchestrated by the central nucleus of the amygdala.
    • Sensory information converges on the lateral and basal nuclei of the amygdala where association formation takes place.
    • Once associations are formed, conditioned responses are orchestrated via the central nucleus and its output to the midbrain (PAG).
    • Opioid-mediated modulation of learning.

    Fear Extinction

    • Extinction: Reduction in Conditioned Response (CR) over time.
    • Distinct Neuron Populations: BA neurons encode fear conditioning and extinction.
      • Day 1 (Habituation): Neither fear nor extinction neurons are strongly activated by the tone.
      • Day 2 (First day of extinction): Fear neurons respond to the tone; extinction neurons do not.
      • Day 3 (Full extinction): Fear neurons do not respond; extinction neurons do.
    • Basal Amygdala: Fear learning and extinction measures.
    • Connections to Infralimbic Cortex:
      • Prelimbic: Fear acquisition.
      • Infralimbic: Fear extinction.
    • Connections to Central Nucleus:

    Spontaneous Recovery

    • Long interval: Rebound in freezing to CS.
    • Short interval: Small rebound in freezing.
    • Evidence for new learning: Extinction is not forgetting but new learning.
      • Spontaneous recovery: Memory re-emerges later.
      • Renewal: Freezing re-emerges when the animal switches to a new context, even after extinction.
      • Reinstatement: Providing a footshock (not following the CS), immediately leads to freezing after the CS.

    Neural Circuits of Fear Extinction

    • CS-noUS Association: New connections develop that suppress expression of the original CS-US association by the central nucleus of the amygdala.
    • Context and CS: Regulate extinction neurons in the basal nucleus and infralimbic cortex, switching ON ITCb cells and inhibiting the central nucleus.

    Hippocampus and Fear Extinction

    • Important for Renewal:
      • Same Context: Low response.
      • Different Context: High response.

    Two Spontaneous Recovery Hypotheses

    • First Hypothesis:

    • Second Hypothesis:

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    Fear Learning & Fear Extinction PDF

    Description

    This quiz explores the intricacies of fear learning and its neurobiological underpinnings. It covers key concepts such as fear conditioning, conditioned responses, and the role of various brain areas in fear processing. Test your knowledge on how fear functions as a defensive system and the physiological responses associated with it.

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