L6: Neurobiology of Addiction Flashcards
(21 cards)
What neurotransmitter is central to addictive behaviors?
Dopamine
Dopamine plays a crucial role in reward learning and motivation.
What is the role of dopamine in the brain?
Involved in:
* Reward (motivation)
* Motor regulation
* Reward processing
* Compulsion
* Emotion and cognition
* Goal-directed behaviour
These functions highlight dopamine’s importance in various mental processes.
What is the nigrostriatal pathway associated with?
Motor regulation
It originates from the Substantia nigra and is impaired in Parkinson’s disease.
What does the mesolimbic pathway process?
Reward, pleasure, reinforcement learning
Primary reward pathway
It connects the Ventral tegmental area (VTA) to the Nucleus accumbens (NAc)
What happens to the mesolimbic pathway when a reward or cue is presented?
Dopamine spikes
This response is crucial for reinforcement learning and addiction.
How do addictive drugs affect the mesolimbic pathway?
Addictive drugs (e.g. cocaine, heoin, nicotine) artificially activate this pathway by:
* Increasing dopamine release
* Blocking reuptake
Frequent exposure leads to stronger cravings and habit formation.
What is the mesocortical pathway linked to?
Cognition, motivation, emotion regulation
- Linked to executive function (decision making, impulse control)
- Dysfunction of this pathway results in impaired control over compulsive behaviours
- ADHD and schizophrenia linked to this pathway
It connects the VTA to the prefrontal cortex
What is the function of the Ventral Tegmental Area (VTA)?
Origin of the mesolimbic and mesocortical dopamine pathways
Contains 50-60% of the neurons that feed into these pathways
It plays a central role in reward learning and goal-driven behavior.
What occurs in dopamine neurons before and after conditioning?
Before: Dopamine spikes when reward is delivered
After: Dopamine increases at the cue/ anticipation of the reward, not the reward
No reward after cure: decreased dopamine firing
This supports the concept of operant conditioning - positive and negative reinforcement
What are the key components of the addiction cycle?
Too much reward (dopamine) → fewer receptors → less pleasure (anhedonia) → increased craving/use → addiction
- Too much reward - dopamine is overstimulated e.g. due to drugs
- Brain tries to restore balance by downregulating dopamine receptors
This cycle explains the neurobiological basis of addiction.
What happens when dopamine receptors are downregualted
- Tolerance (need more for same effect)
- Anhedonia (reduced ability to feel pleasure)
- Craving and compulsive drug-seeking (core features of addiction)
How does dopamine sensitivity relate to personality traits?
Linked with:
* Extraversion
* Sensation-seeking
* Impulsivity
These traits may influence vulnerability to addiction.
What does the COMT enzyme do?
Breaks down dopamine
- Individual variation in dopamine metabolism
- Genetic vulnerability to addiction due to enzyme differences
What is the Endorphins Theory in exercise addiction?
Assumes intense exercise increases endorphins → euphoria
This theory has limitations, such as endorphins not crossing the blood-brain barrier.
What does the Endocannabinoid Theory suggest about exercise addiction?
Runner’s high may be due to endogenous cannabinoids and therefore related to reward expectation and reduction of stress (reinforcemnt)
* These influence reward and pain reduction
* Not physically addictive but reinforce the running behaviour
What neurobiological similarities exist between Internet Gaming Disorder and other addictions?
- Activation in brain regions associated with reward (especially dopamine-related areas)
- Reduced activity in impulse control areas and impaired decision-making
- Reduced functional connectivity in brain networks that are involved in cognitive control, executive function, motivation, and reward
- Neuroimaging evidence shows similar results to drug-abuse research
- Video game-playing stimuli activate the brain similarly to activation by drug cues
These similarities highlight how gaming can activate similar brain regions as substance addictions.
What structural brain changes are observed in alcoholics?
Shrinkage in some studies, but not universally seen
Changes may depend on nutrition and other factors.
What are the behavioral manifestations of alcohol consumption?
1-2 drinks: Increased euphoria and reduction in anxiety
3-5 drinks: Impaired judgment and motor coordination
10-13 drinks: Sedation
More: Memory impairment, loss of consciousness, coma, death
These effects demonstrate the range of alcohol’s impact on behavior.
How does alcohol affect neurotransmitters in the brain?
- Increases dopamine – stimulates pleasure centres and functions in positive reinforcement
- Decreases serotonin – behavioural inhibitor – increased impulsivity and aggressiveness
- Stimulates Opiate neuropeptide release (increases endorphins) – pleasure effects, stimulates further drinking
How does excessive sugar intake affect dopamine?
Activates dopamine release in VTA and sensitises dopamine receptors
This can lead to compulsive sugar consumption similar to drug addiction.
What are the key takeaways regarding dopamine’s role in addiction?
Dopamine plays a central role in:
* Addiction and reward expectation
* Affecting dopaminergic, opioidergic, and GABAergic systems
* Similar activation patterns in alcohol, sugar, and behavioral addictions
Understanding these mechanisms can explain varying vulnerability to addiction.
