Neurobiology of Addiction Behaviour Flashcards
(27 cards)
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ICD-10 of dependence?
AKA addiction - the patient must have the following features:
• Strong desire to take the substance (cravings)
• Difficulties in controlling substance use
• Physiological withdrawal state
• Tolerance
• Neglect of alternative pleasures
• Persistence despite evidence of harm
Examples of addictions?
Drug addiction
Alcohol dependence
Extreme sports (there are signs of tolerance, with individuals progressing to more extreme sports over time)
Pathological gambling (now inc. in DSM-V and recognised as a serious health issue)
Social media
What is CAGE?
Acronym of 4 questions that are used as a screening test for alcohol issues:
• Cut-down (have you ever felt that it would be good to cut-down?)
• Annoyed (have people annoyed you by criticising your drinking?)
• Guilty (have you ever felt guilty about drinking?)
• Eye-opener (have you ever felt that you needed to drink first thing in the morning, i.e: eye-opener, to steady your nerves or to rid yourself of a hangover?)
Define incentive salience?
Cognitive process that attributes a desire/want, inc. a motivational component, to a rewarding stimulus
How does incentive salience prioritise survival?
Identify, select and pursue behaviours that lead to important goals, e.g: food, sex, shelter
These goal need to be prioritised over others
Explain the reward pathway
Ventral tegmental area (VTA) stretches to the nucleus accumbens (in the ventral striatum) and then to the prefrontal cortex; this is the mesolimbic pathway (AKA reward pathway), which is dopaminergic
When presented with something to be desired, dopamine is released in the pathway
Functions of the dopaminergic activity in the mesolimbic pathway?
- A motivating signal
- Incentivises the behaviour
- Involved in normal pleasurable experiences
How do drugs of abuse affect the mesolimbic pathway?
All drugs of abuse will directly/indirectly lead to dopamine release
Explain the concept of tolerance, with relation to the mesolimbic pathway
With dependence, there is decreased response in the pathway
This is due to over-stimulation of the pathway, which leads to the adaptive response of a down-regulation of dopamine receptor availability, resulting in a tolerance to reward
Why does the tolerance to rewards make abstinence difficult?
Down-regulation of dopamine receptor availability persists, despite prolonged abstinence from substance abuse
Normal experiences do not evoke an adequate reward response; this is why patients often relapse after months of abstinence
Define +ve reinforcement, with relation to addiction?
Initial stages of drug-taking is driven by reward, i.e: positive reinforcement
Define -ve reinforcement, with relation to addiction?
Eventually, drug-taking becomes a thirst, i.e: negative reinforcement
Role of the pre-frontal cortex in the mesolimbic pathway?
Helps intention guide behaviour by modulating the powerful effects of the reward pathway
It is inv. with setting goals and focusing attention to make sound decisions; this keeps emotions and impulses under control to achieve long-term goals, rather than simply short-term pleasure
By what age does the pre-frontal cortex fully develop?
Not fully developed until early 20s
Cortical maturation progresses in a back-to-front direction, beginning in the primary motor cortex and spreading anteriorly over the superior and inferior frontal gyri; the pre-frontal cortex develops last
Frontal lobe areas, that mediate executive functioning, mature later than the limbic (emotional) systems; this may be a reason for the higher incidence of RTAs in young adults
Pre-frontal cortex in addiction?
fMRI studies show that there is reduced activity in the pre-frontal cortex
This is difficult to interpret as it could mean either of:
• Drug use affecting the pre-frontal cortex
• Individual’s pre-frontal cortex may have never fully developed, i.e: pre-morbid issue, leading to their drug addiction
Characteristics of adolescents with regards to reward and impulse?
Show:
• Strong stimulus reward
• Minimal judgement or impulse control
Effects of addictive drugs on the pre-frontal cortex?
Effects of dopamine release are:
• Ability to update info within the pre-frontal cortex
• Ability to select new goals
• Ability to avoid compulsive repetition of a behaviour
Addictive drugs provide a potent signal that disrupts normal dopamine-related learning in the pre-frontal cortex
Relationship between age and length of drug use?
Earlier the age at which drug experimentation begins, the longer the relationship with the drugs
Areas assoc. with memory and habit formation?
Hippocampus (declarative learning), striatus (habit learning) and amygdala are critical in the acquisition, consolidation and expression of drug stimulus learning
How do memory and habit formation relate to drug use?
Learned drug associations can cue and trigger internal states of craving, i.e: behaviour around the activity is almost as pleasurable (e.g: removing a cigarette, tapping, rolling, etc)
Role of the orbito-frontal cortex?
Provides internal representations of the saliency of events and assigns values to them
Key creator of the motivation to act
Orbito-frontal cortex activity in addiction?
Addicts show increased activation of the OFC when presented with drug cues
Hyperactivity of this region correlates with self-reported drug cravings, following exposure to cues
These changes persist into abstinence
Brain circuits affected by drug abuse and addiction?
Each of these brain areas and the behaviours they control must be considered when developing strategies to treat drug addiction:
• Pre-frontal cortex and anterior cingulate gyrus - inhibitory control
• Orbito-frontal cortex and sub-callosal cortex - motivation / drive
• Nucleus accumbens and ventral pallidum - reward / salience
• Hippocampus and amygdala - memory / learning
