Neuroplasticity Flashcards
What is the coronal plane?
Splits into front and back
What is the sagittal plane?
Splits into left and right
What is the transverse plane?
Splits into top and bottom
What is hedonic tone?
The trait underlying one’s characteristic ability to feel pleasure
What does the reward circuit control?
Hedonic tone
What is the main target of drugs of abuse?
The striatolimbic reward circuit
What are the 3 pathways in the reward circuit?
- Descending myelinated pathway from the anterior bed nuclei to the ventral tegmental area pathway (VTA)
- Ascending dopaminergic ventral tegmental area to the nucleus accumbens pathway (NAc)
- GABA/substance P/enkephalinergic nucleus accumbens to ventral pallidum pathway
Which pathway in the reward circuit is glutamate driven?
1
What do all addictive drugs do to dopamine levels?
Increase dopamine levels in the NAc
How was the reward circuit evolved?
Evolved to reinforce survival behaviours
What do addictive drugs do to the reward circuit?
Hijacks it
Where is the NAc located?
In the basal forebrain striatum
What is the NAc responsible for?
Pleasure center
Reward/reinforcement of drug-taking - translates emotional stimulus into behaviour
Where does the NAc project to?
VTA
PFC
Amygdala
Hippocampus
Basal ganglia
What interface does the NAc control?
The interface between limbic and motor systems
Where is the VTA located?
In the midbrain
What is the VTA responsible for?
Main driver of rewarding feelings
Involved in cognition, motivation, and locomotor activity
Where is the PFC located?
In the frontal lobe
What is the PFC responsible for?
Self-awareness, personality, executive function
What pathway from the PFC relate to the expression of behaviours trained by chronic drug abuse?
PFC -> VTA + amygdala
Where is the hippocampus located?
In the para-sagittal plane, caudal amygdala
What is the hippocampus responsible for?
Memory formation, processing novel and contextual information
What does the hippocampus contain that is suppressed by drugs of abuse?
Neuronal stem cells
What pathway modulates plasticity and learning/memory?
VTA -> Hippocampus
What is the amygdala responsible for?
Emotions, learning, memory, reward, attention, arousal, stress
What is the amygdala key for?
Emotional reactivity - most disabling symptom in addicts
What disrupts amygdala -> PFC connections?
Chronic drug abuse
What does the basolateral amygdala permit?
Emotional regulation, decision making by medial PFC
What is the caudate nucleus responsible for?
Voluntary movement, learning, memory, sleep, pain, social behaviour
Where do drugs accumulate?
In the caudate nucleus, drugs bind to receptors here
Where is the locus coeruleus located?
In the dorsal pons
What is the locus coeruleus responsible for?
Regulates arousal, cognition, memory, sleep-wake, attention, emotion, stress
What is the locus coeruleus particularly important for?
Stress responses
LC-NE afferents are modulated by the K opioid receptor activation
What part of the brain regulates withdrawal symptoms?
The locus coeruleus
Where are the raphe nuclei located?
In the dorsal medulla oblongata
What are the raphe nuclei responsible for?
Regulating mood, emotion, aggression, sleep, anxiety, memory, appetite, pain, and temperature
What are nuclei and forebrain projections targets for?
Alcohol, opioids, MDMA
What have RN->PFC projections been implicated in?
Neuropsychiatric disorders like OCD, ADHD, and schizophrenia
What is drug-taking behaviour initially?
Reward-driven
What is impulsivity?
A collection of multidimensional behaviours
Incorporate state and trait classifications
How do we measure impulsivity?
Self-reports, behavioural scores, electrophysiology
What does deficient frontostriatal “top-down” cognitive control result in?
An inability to override thoughts that leads to actions
Unable to prevent dangerous actions from occurring
What activity is mainly involved in impulsivity?
Dorsalateral prefrontal activity
There is a high association between impulsivity and what?
The incidence of substance use disorders
What is the trait effect of impulsivity?
Mostly made up of decreased cognitive and response inhibition
What is the state effect?
Acute and chronic use of drugs change brain structure and function
What is compulsivity?
A tendency toward repetitive and habitual actions even when it harms you
What are the effects of compulsivity?
Decreased voluntary control over urges
Diminished ability to delay or inhibit compulsive behaviours
A tendency to perform repetitive acts in a habitual or stereotyped manner
What can repeated administration of addictive drugs lead to?
Compulsive drug-seeking behaviour
What is at the core of the reward circuit?
VTA -> NAc DA-ergic projections
What is at the core of anticipation circuits?
Front inputs (PFC)
What is at the core of reinstatement/relapse circuits?
The amygdala
What happens when drugs lose their euphoric effects?
Users continue taking the drug so they can achieve baseline cognitive function
What is neuroplasticity?
An ability to form new connections, change wiring patterns, and establish new pathways in neural re-wiring
What does the repeated firing of neurons induce?
Long-term changes via molecular signaling and transcriptional changes
What potentiates new goal-directed circuits?
Striatal dopamine and glutamate
How does addiction start?
Occasional recreational use then impulsive use then habitual compulsive use
Goes from reward-driven behaviour to goal-driven drug-seeking behaviour
What shift in control does addiction correlate with?
A ventral striatum-to-dorsal-striatum-mediated shift in control of drug-seeking behaviour
What is tolerance?
Taking more drug without feeling effects or needing more of the drug to feel the same effect
What is withdrawal?
Generally unpleasant affective moods and symptoms
What is addiction triggered by?
Reward circuit activation and neuroplasticity in other regions
What is dependence triggered by?
Tolerance/Withdrawal
Are addiction and dependence the same?
No, it is possible to be dependent on a drug (anti-hypertensives, pain meds) without being addicted
