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NeuroEndo Exam 3 > Neurophysiology of Reward and Addiction (Pierce) > Flashcards

Neurophysiology of Reward and Addiction (Pierce) Flashcards

1
Q

What is motivation?

A

A process that mediates goal-directed responses or goal-seeking behavior to changes in the external or internal environment

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2
Q

What is saliency?

A

Something important in the surrounding env. worth paying attention to; the attention-grabbing feature of rewarding objects.

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3
Q

What does reward involve?

A
  1. hedonic effect of pleasure
  2. motivation to obtain the reward because of its value
  3. Associated learning
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4
Q

What is aversion?

A

A negative reinforcement of behavior that the individual will learn to avoid future encounters

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5
Q

What is pleasure?

A

A subjectively positive sensation

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6
Q

What is the purpose of pleasure?

A

To promote behaviors that are consistent with survival of self and the species.

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7
Q

What NT plays a role in pleasure reward seeking behavior?

A

Dopamine

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8
Q

What do DA neurons encode

A

The discrepancy between reward prediction and information about the actual reward received and broadcast the signal to downstream brain region involved in reward learning.

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9
Q

How do drugs of abuse affect dopamine concentration?

A

Will increase extracellular concentration of dopamine in limbic regions, including the nucleus accumbens (NA) and prevent reuptake of dopamine

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10
Q

How do drugs increase dopamine and by how much?

A
  • Directly: Inhibiting dopamine reuptake or promoting dopamine release
  • Indirectly: Using other neuron receptors that modulate dopamine levels

5-10 fold increase than natural reinforces such as food and sex

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11
Q

What is salience?

A

A stimuli or environmental changes that are arousing or that elicit an attentional behavioral switch

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12
Q

Why are addicts at a great risk for relapse when they visit places they had taken drugs at?

A

The stimuli around them are salient (noticeable). The stimuli itself can increase dopamine and elicit desire for drugs.

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13
Q

What are important brain regions in the mesolimbic system

A

Nucleus Accumbens (NA)

Ventral tegmental area (VTA)

Prefrontal cortex (PFC)

Limbic system

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14
Q

What is the main function of the nucleus accumbens?

A

Suppress sensations of pleasure and reward

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15
Q

What structures constitutively activate (via EAA like glutamate) nucleus accumbens?

A

Hippocampus

Amygdala

Prefrontal cortex (PFC)

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16
Q

What type of neurons does the nucleus accumbens release?

A

GABA (inhibitory)

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17
Q

What is the basic/default circuit of pleasure

A
  • Hippocampus, amygdala & prefrontal cortex release constant trickle of EAA to NA
  • NA neurons release GABAergic (inhibitory) neurons to PFC
  • Constituitive inhibition of PFC targets keeps the brain in a reward-neutral state (no pleasure)
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18
Q

What pathway occurs when you do something that elicits a reward?

A
  1. Dopamine neurons synthesized in VTA project to nucleus accumbens.
  2. Dopamine released into NA inhibits it.
  3. NA activity decreases, resulting in a sensation of pleasure

When NA actvity decreases, it can’t inhibit targets in the prefrontal cortex

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19
Q

What stimulates the VTA when you engage in behavior or activity that results in rewards?

A

Pre-frontal cortex: EAA

Dorsal Tegmental area: ACh

Hypothalamus: Orexin (from food)

20
Q

What suppresses the VTA to prevent additional release of dopamine and halt the reward process

A

Projections from the NA back to the VTA which release GABA and a opiod co-transitter called dynorphin

21
Q

What is the dopamine-hypothesis of reward?

A

Inactivation of Nucleus Accumbens via dopaminergic neurons from VTA

22
Q

What is the dopamine-independent reward pathway

A

Utilizing endogenous opiods to activate the reward pathway

23
Q

What activities can increase endogenous opioid signaling?

A

Exercise

Ethanol

Other activities

24
Q

What receptors do opioid signaling utilize to activate dopaminergic receptors at VTA?

A

Mu receptors

25
Q

How does opioid signaling work?

A
  1. Inhibit local VTA interneurons that normally suppress dopaminergic neurons in VTA
  2. Disinhibit dopaminergic neurons
  3. Activate nucleus accumbens local interneurons to inhibit the release of GABA
  4. Activate pre-frontal cortex
26
Q

What is the result of endogenous opioid signaling?

A

Pleasure

Euphoria

27
Q

From a neurobiological perspective, what does addiction probably result from?

A

Recurrent supraphysiologic perturbations in dopamine system. Chronic drug exposure alters the morphology of neurons in dopamine-regulated circuits

28
Q

How can drugs change things at a cellular level?

A

Alter expression of certain transcription factors and proteins involved in neurotransmission in brain regions regulated by dopamine

29
Q

How can drugs change things at a neurotransmitter level?

A

Abnormal NT levels for dopamine, glutamate, GABA, opioids, serotonin

30
Q

Where are lasting memories of the good feelings associated with drugs created?

A

Memories made in hippocampus

31
Q

What brain region mediates craving?

A

Amygdala

32
Q

When the abuser seeks out drugs, what structure is involved in the poor decision making?

A

Orbitofrontal cortex

33
Q

What is the short term mechanism of memory in reward and addiction

A

Increased phosphorylation of AMPA receptors in the post-synaptic membrane

34
Q

What is the long term mechanism of memory in reward and addiction

A

Activation of calcium-calmodulin-CREB mechanism

35
Q

What is the life long mechanism of memory in reward and addiction

A

Signaling cascade involving transcription factors - change FosB and AP-1

36
Q

How does the activation of calcium-calmodulin-CREB mechanism work?

A

Promotes production of dynorphin in nucleus accumbens to shut off VTA and dopaminergic signaling

37
Q

What is physical dependency?

A

Chronic use of a tolerance-forming drug, in which abrupt or gradual drug withdrawal causes unpleasant physical symptoms

38
Q

Why does physical dependency occur?

A

Excessive noradrenergic output from the locus ceruleus (involved in arousal and vigilance), and CREB dependent up-regulation of target genes in locus ceruleus.

39
Q

When are the FosB and AP-1 genes up-regulated?

A

Chronic Stress

Drugs of Abuse

40
Q

How do natural reinforcers (food, sex, exercise) differ from drugs?

A

Natural Reinforcers: Firing of neurons stop when event concludes

Drugs: Dopamine release continues after activity

41
Q

How does dopamine change the reward circuitry?

A

Dopamine can alter a fearful stimuli to a pleasurable one Ex: Before hearing a bell could be scary, but now hearing a bell is associated with euphoria from drugs

42
Q

How do addicted brains differ from non-addicted brains?

A

Conditioned cues reinforce saliency of substances, increasing behavior to find and consume drugs. These cues override prefrontal cortex’s control of behavior

43
Q

What role does the substantia nigra and dorsal striatum play in pleasure/reward-seeking behavior?

A

Control motor response associated with navigating the environment for desirable activity

44
Q

What are differences between conditioned responses and drug-associated cues?

A

Conditioned responses: cues to drug-taking in specific social circumstances

Drug-associated cues: powerful cues that can elicit drug urges and physiologic responses w/o taking drug

45
Q

What role does the locus ceruleus play?

A
  • Involved with physiological responses to stress and panic
  • Synthesis of norepinephrine
46
Q

What does CREB mediate in the locus ceruleus?

A

Physical dependency due to excessive noradrenergic output from locus ceruleus

47
Q

How does dopamine alter the conditions through which fear occurs

A
  1. Alters the association itself - attaching rewarding hedonic value to previously fearful stimuli
  2. Alters the expression of the memory

NeuroEndo Exam 3 (16 decks)

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