6. Reward, Pain, and Fear
Studied by 0 people
Learn
Practice Test
Spaced Repetition
Match
Flashcards1/80
There's no tags or description
Looks like no tags are added yet.
Name | Mastery | Learn | Test | Matching | Spaced |
|---|
No study sessions yet.
81 Terms
What is a reward?
A positive reinforcer that strengthens behavior by increasing the likelihood of an action being repeated.
What is the key dopaminergic pathway involved in reward?
The mesolimbic dopamine pathway, from the Ventral Tegmental Area (VTA) to the Nucleus Accumbens (NAc).
What was the significance of the Olds and Milner study?
Demonstrated that rats would self-stimulate the medial forebrain bundle, showing that specific brain regions mediate reward.
What is the medial forebrain bundle (MFB)?
A fiber tract connecting the VTA to the NAc and forebrain; electrical stimulation here is strongly rewarding.
What are primary reinforcers?
Innate rewards like food, water, sex — necessary for survival.
What are secondary reinforcers?
Learned rewards like money or praise — gain value through association.
What is the difference between wanting and liking?
Wanting = motivational drive (dopamine); Liking = hedonic pleasure (opioids, endocannabinoids).
Which neurotransmitter mediates wanting?
Dopamine.
Which neurotransmitters mediate liking?
Opioids and endocannabinoids.
What is incentive salience?
A learned motivational importance attributed to a stimulus or cue due to its association with reward.
Who proposed the incentive salience theory?
Berridge and Robinson.
What happens to dopamine activity when a reward is better than expected?
Dopamine neurons increase firing — positive prediction error.
What happens when a predicted reward is omitted?
Dopamine firing decreases — negative prediction error.
What happens when a predicted reward is received?
No change in dopamine activity — the system is calibrated.
How does cocaine affect dopamine signaling?
Blocks dopamine reuptake, increasing dopamine concentration in synapses — leads to euphoria and reinforcement.
How do amphetamines affect dopamine signaling?
Increase dopamine release and reverse reuptake transporters — massive boost in synaptic dopamine.
Why are hedonic drugs so addictive?
They hijack the reward system by causing artificial surges in dopamine, reinforcing drug-seeking behavior.
What brain regions are involved in the reward circuit?
VTA, Nucleus Accumbens, Amygdala, Orbitofrontal Cortex, Hippocampus, Prefrontal Cortex.
What is the role of the orbitofrontal cortex (OFC) in reward?
Assigns value to rewards and helps guide adaptive decision-making.
What is the role of the amygdala in reward?
Associates emotional significance to rewards and their cues.
What does the hippocampus contribute to reward?
Encodes contextual information about where and when a reward occurred.
How is the basal ganglia involved in reward?
Via a limbic loop: reward signals from cortex → ventral striatum (incl. NAc) → pallidum → thalamus → back to cortex.
How is the limbic loop different from the motor loop in the basal ganglia?
It processes emotional and motivational information, not movement.
What are the four key actions of dopamine in the diffuse modulatory system?
- Motivational salience (reward prediction), 2. Reinforcement learning, 3. Modulation of attention, 4. Motor activation (esp. via basal ganglia).
How is dopamine dysregulated in addiction?
Excessive dopaminergic signaling assigns high salience to drug cues, driving compulsive behavior.
What reward dysfunction is seen in depression?
Blunted dopamine response → reduced reward sensitivity and motivation (anhedonia).
How does schizophrenia involve dopamine and reward?
Abnormal dopamine signaling leads to aberrant salience, making neutral stimuli feel important or threatening.
What type of action does dopamine have in the brain?
Dopamine acts as a neuromodulator and state switcher, influencing brain state rather than direct synaptic transmission.
What is the structure of dopaminergic nuclei?
Dopaminergic action originates from a nucleus or small cluster of nuclei containing thousands (not millions) of neurons.
Where are most dopaminergic nuclei located?
In the central core of the brain: the brainstem and basal forebrain.
What is meant by dopamine’s “highly divergent projection”?
Each dopaminergic neuron can influence hundreds of thousands of neurons across vast brain regions.
What type of synapses do dopaminergic neurons make?
They form en passant synapses—synaptic boutons along the axon, allowing widespread, diffuse signaling.
What is the official definition of pain according to the International Association for the Study of Pain?
An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.
What is the difference between pain and nociception?
Pain is a subjective experience, whereas nociception is the neural process of encoding and processing noxious stimuli.
What are nociceptors?
Nociceptors are sensory neurons that detect signals from damaged tissue or potential damage and transmit this information to the brain.
What are the three main types of pain?
Nociceptive pain (from tissue damage), inflammatory pain (from inflammation), and neuropathic pain (from nerve damage).
What are the two types of peripheral nociceptors based on conduction velocity?
Aδ fibers (thinly myelinated, faster, sharp pain) and C fibers (unmyelinated, slower, burning pain).
What is TRPV1 and what activates it?
TRPV1 is a receptor found on nociceptors that is activated by capsaicin and high temperatures (>42°C).
Where do peripheral nociceptors first synapse in the CNS?
In the dorsal horn of the spinal cord, often with second-order neurons that cross and ascend.
What is the spinothalamic tract responsible for?
It transmits pain and temperature signals from the body to the somatosensory cortex via the thalamus.
What is sensitization in the context of pain?
Increased responsiveness of nociceptors to normal or sub-threshold stimuli, often seen in chronic pain.
What are hyperalgesia and allodynia?
Hyperalgesia is increased pain from a normally painful stimulus. Allodynia is pain from a normally non-painful stimulus.
What is neurogenic inflammation?
Inflammation caused by the release of peptides like substance P and CGRP from activated nociceptors.
What is descending modulation of pain?
The process where brain areas send signals down to the spinal cord to inhibit or modulate incoming pain signals.
What are the actions of common analgesics on pain pathways?
NSAIDs block prostaglandins, local anesthetics block sodium channels, opioids enhance descending inhibition, and paracetamol works via unknown central mechanisms.
What role does the dorsal horn of the spinal cord play in pain processing?
The dorsal horn of the spinal cord is the first central site where peripheral nociceptors synapse onto second-order neurons. It processes and modulates incoming nociceptive signals before they ascend to the brain.
Which ascending pathway transmits the discriminative aspects of pain and temperature from the body to the brain?
The anterolateral system, particularly the spinothalamic tract, transmits discriminative aspects of pain and temperature to the thalamus and then to the primary somatosensory cortex.
What is the function of the anterolateral system?
The anterolateral system transmits noxious and thermal stimuli from the contralateral side of the body, following decussation in the spinal cord, to supraspinal centers including the thalamus and cortex.
What is the dorsal column-medial lemniscal system responsible for?
The dorsal column-medial lemniscal system carries fine touch, vibration, and proprioceptive information from the body to the brain, not pain or temperature.
Which supraspinal centers are involved in the affective and cognitive processing of pain?
Supraspinal centers include the thalamus, anterior cingulate cortex, insular cortex, amygdala, and prefrontal cortex, all contributing to the emotional and evaluative dimensions of pain.
Who was Henry K. Beecher and what did he observe about pain?
Henry K. Beecher was a physician who observed that wounded soldiers in WWII often reported less pain than expected, suggesting that psychological factors like context and emotional state modulate pain perception.
What are the implications of Henry Beecher’s findings on pain perception?
Beecher’s findings highlight the importance of descending modulation and psychological context in pain perception, paving the way for understanding pain as more than just a sensory experience.
What brain structure is central to fear processing?
The amygdala, especially the basolateral and central nuclei, processes and expresses fear.
What is the function of the basolateral amygdala in fear?
It receives sensory input and forms associations with emotional significance, key for fear learning.
What does the central nucleus of the amygdala do in fear?
It initiates autonomic and behavioral fear responses via projections to the hypothalamus, brainstem, and cortex.
What is classical fear conditioning?
A neutral stimulus becomes associated with an aversive event, leading to a conditioned fear response.
What pathways mediate auditory-somatic association in rats?
The auditory pathways project to the medial geniculate nucleus, which projects to both the auditory cortex to register sound, and amygdala (where other projections meet), then output to other circuits for somatomotor and autonomic activity.
What happened in the case study of patient S.M.?
S.M. had bilateral amygdala damage and showed impaired fear recognition and no fear responses despite dangerous situations.
What are the pyramidal and extrapyramidal contributions to fear behavior?
Pyramidal pathways (corticospinal) mediate voluntary reactions; extrapyramidal systems mediate involuntary expressions and reflexive behaviors like freezing.
What is fear extinction?
Gradual reduction of a conditioned fear response through repeated exposure without the aversive stimulus.
Which brain areas regulate fear extinction?
The medial prefrontal cortex (infralimbic cortex) suppresses amygdala activity; hippocampus provides contextual control.
What are the components of the limbic lobe involved in emotion?
Cingulate cortex, parahippocampal gyrus, amygdala, hippocampus, and hypothalamus form the limbic lobe network.
What is the role of the prefrontal cortex in fear regulation?
It exerts top-down control, particularly via the infralimbic region, to inhibit amygdala-driven fear responses.
What is the periaqueductal gray (PAG) responsible for in fear?
It mediates instinctive defensive behaviors such as freezing or fleeing in response to fear cues from the amygdala.
What strategies are used to normalize excessive fear responses?
Exposure therapy, cognitive reappraisal, pharmacotherapy (e.g. SSRIs, propranolol), and neuromodulation like TMS or DBS.
What disorders involve abnormal fear circuitry?
PTSD, phobias, and generalized anxiety disorder — often due to hyperactive amygdala or deficient extinction pathways.
How does the hypothalamus contribute to fear?
It mediates autonomic (sympathetic) and neuroendocrine responses, including cortisol release via the HPA axis.
What is the importance of the medial geniculate nucleus (MGN) in fear associations?
The MGN of the thalamus relays auditory information to the amygdala, enabling the association of sounds with aversive stimuli during fear conditioning.