Neurobiology of Addiction and Opiates Flashcards
outline the dopaminergic reward pathway
which 2 drugs cause the most significant increase in dopamine release
ampethamines and cocaine
what is the reward pathway involved in
it acts as a motivating signal, incentivises behaviour
it is involved in normal pleasurable experiences
what happens when you over stimulate the reward pathway, eg take too many drugs
the dopamine receptors downregulate, so a tolerance to reward is developed
this means the theshold for all rewards is increased - normal experiences arent pleasurable and more drug is reuqired for same effect
is downregulation of the dopamine receptors in reward pathway reversible?
yes?? over time, but the changes persist despite prolonged abstinence - this is a trigger for relapse
what is positive reinforcement
reinforcing stimulus, eg money for doing homework
what is negative reinforcement
an annoying stimulus is removed after a particular behavour, eg nagging stopped after dishes done
is drug addiction drive by positive or negative reinforcement
positive in the initial stages
negative in the later (eg to get rid of withdrawals, life seems dull)
what is the role of the prefrontal cortex
planning complex cognitive behaviour, personality expression, decision making and social behaviour
keeps emotions and impulses under control to achieve long term goals –> puts the breaks on the reward pathway
where does cortical maturation begin and end
back to front, from Mi to frontal gyri, prefontal cortex develops last
what is the significance of the late development of the pre frontal cortex
it is not fully developed till 20s (marshmallow test)
this means that the parts of the brain that control exectuive functioning mature later than limbic (emotional) systems –> teens show strong stimuls reward, minimal judgement and impulse control
what is the significance of starting addictions early
the PFC is vulnerable during development
synpatic plasticity - the earlier drugs start the longer the relatonship is
what effect can learned drug associations have
can cue internal states of craving eg opening a fag packet
what is the role of the orbito frontal cortex in addiction
provides an internal representation of the saliency of events and assigns a value to them –> creates a motivation to act
in addicts, this area is activated a lot when they are presented with a drug cue –> craving
how is the PFC affected by addiction
PFC is dysfunctional - no longer putting breaks on reward pathway or OFC
too much dopamine going around
do genetics have an influence on addiction?
Yes! large
They may affect: the way we respond to drugs metabolically; behavioural traits that predispose us to take drugs; how rewarding we find drug taking. Influence receptor levels, e.g. if there are low dopamine receptors there is a higher risk.
