Neurobiology of Addiction Flashcards
what are the criteria for dependence
a strong desire to take the substance difficulties in controlling substance use a physiological withdrawal state tolerance neglect of alternative pleasures persistence despite evidence of harm
what is incentive salience
attributing want to a stimulus
what are the parts of the motivational pathway
originates in VTA (ventral tegmental area)
- > nucleus accumbens
- > prefrontal cortex
what is the role of dopaminergic activity in the mesolimbic pathway
is a motivating signal, incentivises behaviour, is involved in normal pleasurable activities
what do drugs cause in motivational pathway
release of dopamine in the nucleus accumbens
how is tolerance seen in MRI
less blood flow to the striatum upon rewarding stimulus
what receptors are decreased in addiction and why
dopamine D2 receptors
due to repeated dopamine release- receptors down regulate
what does decreased D2 receptors in addiction mean
threshold for reward during abstinence is increased- normal experiences don’t evoke adequate reward response
these changes persists even after prolonged abstinence from abuse
what happens to the positive reinforcement of taking a drug in addiction
becomes negative reinforcement (removal of adverse stimulus - a thirst for the drug)
what is the role of the pre frontal cortex
helps intention guide behaviour
modulates the powerful effects of the reward pathway
sets goals, focuses attention
makes sound decisions
keeps emotions and impulses under control to achieve long term goals
involved in executive function
when does the prefrontal cortex stop developing
early 20s
what happens to the PFC in addiction
reduced activity and glucose metabolism
why does an earlier age of drug experimentation lead to a longer relationship with drugs
as PFC still developing until 20s
- synaptic plasticity
- long term potentiation and depression
what is the role of the hippocampus, striatum and amygdala in addiction
acquisition, consolidation and expression of drug stimulus learning
Learned drug associations can cue internal states of craving (the sight of cigarettes/ rolling them releases dopamine making you want to smoke more)
what is the role of the orbito-frontal cortex in addiction
provides internal representation of salience of events and assigns value to them
key creator of motivation to act
addicts show increased activation here when presented with drug cues
is influenced by both the nucleus accumbens and the prefrontal cortex, decides whether or not you do it
what is the role of the nucleus accumbens
involves in wanted substance/ behaviour
where dopamine is release
influences OFC
what is the role of the prefrontal cortex
stops actions, tries to make sound decisions
how much of addiction risk is genetic
40-60%
how do genetics influence out addiction risk
the way we respond to drugs metabolically
behavioural traits that predispose up to take drugs
how rewarding we find taking drugs
how levels of what receptors increases your addiction risk
DRD2
how does stress influence addiction
acute stress trigger the release of dopamine in neural reward pathway
rapid increase can motivate drug seeking in dependent individuals
chronic stress leads to dampening of dopaminergic activity through the down regulation of D receptors
this reduces sensitivity to normal rewards, encourages exposure to highly sensitive rewarding behaviours
what are the core features of addictive behaviour
salience (importance, dominance)
mood modification (rush and escape)
tolerance (escalation for effect, increasing intensity, recklessness, destructiveness)
withdrawal
conflict (interpersonal, intrapsychic, loss of control)
relapse
what is the moral model of addiction
where individual is primary causal factor- result of human weakness
wilful violation of societal rules
what part of brain is involved with the withdrawal/ negative effects
amygdala
what is conditioning
the process of behaviour modification whereby an individual comes to associate a desired behaviour with a previous unrelated stimuli
what group of people are at very high risk of overdose
those who have just been released from prison (loose tolerance)
what is instrumental value
learning by connecting the consequences of actions with the preceding behaviour
what is positive and negative reinforcement
positive applies stimulus
negative removes stimulus
both increase the frequency of the behaviour that produces them
what is associative learning
through repeated pairing with a cue a previously neutral stimuli will come to elicit the same response
what is habit formation
an acquired behaviour pattern regularly followed until it becomes almost involuntary
how is attention and memory bias involved in addiction
selective recall (forget bad things) bias towards detection of addiction related cues
