Cognitive Neuroscience of Addiction Flashcards
1
Q
What are some of the reasons for using psychoactive substances?
A
- alcohol to relax, sleep, enhancing social experiences, reduce anxiety/feelings of depression
- coffee to wake up
- nicotine for experience, stimulant, social reasons
- MDMA to improve social experiences
- cocaine to be more confident, focus more, enhance experiences
- heroin to relax
2
Q
What is addiction?
A
- addicts experience intense cravings for desired substance, severe withdrawals
- extreme lengths to obtain drug
- can have profound effect on families, work, education, social life
- degrees to which these things happen differ greatly between people and the drugs/behaviours
3
Q
What are the drugs that people get addicted to?
A
- those associated with addiction: nicotine, alcohol, amphetamine, caffeine, heroine, cocaine, cannabis, prescriptions
- drugs less associated with addiction: MDMA, psychedelics
4
Q
What is the neuropathology of cocaine?
A
- associated with a number of brain damage risks appearing minutes to hours after cocaine consumption, including stroke in young adults in their early thirties, seizures, lesions resulting in movement disorders
- more subtle pathology includes reduced volume of the inferior portion of the frontal lobe
5
Q
What is the neuropathology of heroin?
A
-associated with a broad range of neuropathologies including reduction in grey matter, brain hypoxia (reduced oxygen availability), cerebral edema (water saturation), stroke (loss of blood supply), spongiform leukoencephalopathy (general loss of brain white matter) and myelopathy (paralysis produced by spinal lesions)
6
Q
What is the neuropathology of alcohol?
A
- strongly linked to the Wernicke-Korsakoff syndrome
- Wernicke encephalopathy is the general brain shrinkage shown below
- Korsakoff syndrome is the chronic ‘end stage’ of this phenomenon. It is a psychiatric diagnosis characterized by anterograde amnesia, which can sometimes be treated with thiamine supplements
- brain of an alcoholic with Wernicke-Korsakoff may show enlarged ventricles and cortical sulci (indicating loss of brain tissue)
7
Q
What is the neuropathology of cannabis?
A
- Yucel et al (2008) carefully selected long-term (>10 years) heavy (>5 joints daily) cannabis-using men with an average of 19.7 years of use no history of other neurologic/mental health complications, contrasted them with 16 control subjects
- brain volume was reduced in users in the hippocampus and the amygdala
8
Q
What is the relation of cannabis and psychosis?
A
- 1 way of testing whether drug use causes mental illness is large scale longitudinal research which assesses the psychiatric status of youth prior to drug use, and then tests them again in adulthood after some had used cannabis
- odds ratios shown for several studies below reflect the increased risk of diagnosis of psychotic symptoms in individuals who had engaged in heavy cannabis use compared to those who had not. An odds ratio of 1 means that the groups have equal risk. However, the average odds ratio was 2.09, indicating a doubling of the risk of psychotic symptoms given heavy cannabis use
9
Q
What are the causes of addiction?
A
- there’s large inter-individual variability in susceptibility to addiction
- about 10-20% of users become addicted
- estimated that genetic contribution to addiction is about 50%
10
Q
What is the learning perspective of addiction?
A
- associative learning theories of addiction construe drug taking as conditioning
- in the instrumental conditioning paradigm, the drug is the reinforcer which strengthens the associations between drug-related cues and the drug use
- effect of a drug is US and cues associated with its administration are CS
- context-driven relapse has been extensively documented in rehabilitation, when they are re-exposed to the cue that elicits the CR
- extinction procedures that involve exposure to multiple cues without the reward can be effective, because one reduces their potency in triggering the relapse
- research suggests that extinction treatments limited to rehabilitation centers are less effective, long term, than treatments carried out in contexts equivalent or similar to those in which addiction developed
11
Q
What is the conditioned compensatory response?
A
- victims of heroin overdose are seldom novices thus repeated use leads to a conditioned compensatory response
- often cases of overdose involve some significant change in the context that the drug is taken
- alcohol has a stronger effect when consumed as part of exotic drinks/cocktails than when it’s part of familiar drinks as the change in taste reduces the conditioned compensatory response. One tends to get drunk more easily in the company of unfamiliar people compared to that of old friends as the change of company reduces the conditioned compensatory response
12
Q
What is tolerance?
A
- conditioned compensatory response is a form of tolerance to the effects of the drug
- effects of tolerance are complex
- is a form of homeostatic protection to reduce the potentially harmful effects of the drug
- tolerance can lead to overdose if the conditions necessary for it to work are absent
- tolerance also often results in an increase in the dose because larger and larger doses are required to achieve the desired effect
- homeostatic protection mechanisms that underlie tolerance can increase the additive potential of a drug. This is because the physiological mechanisms that underlie tolerance can contribute to withdrawal symptoms
13
Q
What is the conditioned compensatory response to alcohol?
A
- tolerance to alcohol is based on the desensitisation of GABA receptors where alcohol is an agonist
- whilst this has a protective role when alcohol is consumed, when consumption is ceased it leads to imbalance between excitation and inhibition in the brain resulting in psychological and motor agitation characteristic of alcohol withdrawal
- to prevent excess inhibition, the organism compensates by reducing the sensitivity of GABA receptors in inhibitory synapses and by increasing activity in excitatory synapses
14
Q
What is the relation to tolerance and withdrawal?
A
- heroin reduces heart rate and blood pressure
- tolerance results in raising the blood pressure and heart rate
- when discontinued, this leads to abnormally high blood pressure and heart rate
- withdrawal symptoms are caused by the prior adjustments in the nervous system to combat the effects of a drug when the drug is no longer there
- gives rise to craving, a motivational state akin to hunger, you adapted system is motivating you to seek the drug
- avoiding withdrawal and craving are believed to be one of the primary factors promoting addiction
15
Q
How can drugs be rewards?
A
- whilst drug-related cues and avoidance of withdrawal can go some way in explaining the addictive potential of drugs of abuse, they don’t seem to capture the whole picture of addiction
- don’t explain why someone who stopped taking drugs a relatively long time ago and doesn’t experience severe withdrawal or isn’t exposed to drug-related cues, may still relapse
- conditioning-based models of addiction also find it hard to account on their own for the fact that drugs of abuse become increasingly desires wit use
- limitations of cue reactivity and withdrawal models, along with the discovery of the dopaminergic circuits and their importance for processing of naturally rewarding stimuli, gave rise to the idea that drugs of abuse may be addictive because they’re exceptionally rewarding
