fMRI and the Neurobiology of Addiction Flashcards Preview

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How does functional MRI work?

It uses changes in the magnetic properties of the blood as oxygen is removed to measure the ratio change in oxyhaemoglobin to deoxyhaemoglobin in venous blood (the BOLD signal). As neuronal activity requires oxygen, it functions as an indirect measure of neuronal activity


Why might fMRI be able to detect biomarkers in addiction?

Substances of addiction disrupt behavioural and cognitive processes governed by neural activity, including those involved in motivation and reward. fMRI can locate these disturbances at a population level


State 4 key brain elements of addiction

Behavioural control, decision making, emotional reactivity, and reward sensitivity


How might neural activity be changed in addiction?

One model suggests that there is a change in the weighting of networks, giving the nucleus accumbens, amygdala, and orbitofrontal cortex less inhibitory control and leading to continued pursuit of the addictive substance


Describe the dopamine reward deficiency syndrome hypothesis of addiction

Addiction is a deficit in dopamine circuitry for non-drug rewards, and only the substance(s) of addiction can produce a normal reward response


State a piece of evidence against the dopamine reward deficiency syndrome hypothesis of addiction

Some drug users show a general hyperresponsivity to all types of rewards


Name some brain regions involved in the reward circuitry of the brain

Substantia nigra, ventral tegmental area, amygdala, hippocampus, prefrontal cortex, ventral striatum


Describe how hijacking the reward circuitry can increase the likelihood of relapse, with an example

Nothing becomes as rewarding as the thought of using the drug. A 2014 study by Sweitzer et al found that, in smokers, monetary reward caused greater brain activation than the thought of smoking - but in abstinent smokers, imagining smoking a cigarette caused greater brain activation


Define cognitive control

Processes which allow behaviour to vary adaptively from moment to moment - e.g. response inhibition


Describe the relationship between cognitive control and drug use or relapse

Poorer cognitive control may make people more susceptible to drug use and relapse, and it predicts poor treatment adhesion


Name some brain areas involved in cognitive control networks

Anterior cingulate cortex, dorsolateral prefrontal cortex, inferior frontal junction, anterior insular cortex, dorsal pre-motor cortex, posterior parietal cortex


Describe the results of Hester et al's 2009 study on cognitive control in chronic cannabis users

Chronic cannabis users had impaired error awareness and hypoactivity in their anterior cingulate cortex


Describe the results of Hester & Garavn's 2004 study on cognitive control in cocaine users

Cocaine users had hypoactivity in their right superior frontal gyrus, right pre-SMA, and left anterior cingulate cortex than healthy contrains during a memory response task


Describe the subjective association between stress and relapse

Clinical observations show an association between self-reports of stressors and a subsequent return to drug or alcohol use


Describe the results of Paulus et al's 2005 study into predicting relapse using fMRI

Abstinent methamphetamine addicts who would later relapse had less activation of decision-making areas during decision-making tasks than those who would remain abstinent


Describe the results of Gowlin et al's 2014 study into predicting relapse using fMRI

There was greater activation of the anterior insula when processing risk in those who remained abstinent than those who would later relapse


How could fMRI aid in the development of new medication to treat addiction?

It could identify the brain regions involved and show the effects of new medications on the brain


State some limitations of fMRI

High numbers of artefacts (e.g. from movement or breathing), scanner doesn't simulate everyday life, not a direct measure of neuronal activity, claims made are simplistic based on location


State some potential uses of fMRI

Improve understanding of underlying brain mechanisms, distinguish healthy from at risk from diseased brains, predict the risk of disease development and progression, identify markers of relapse or resilience, predict treatment response


Where does most knowledge of brain addiction come from?

Animal studies


What is the main disadvantage of animal models to study addiction?

Humans often have confounders - e.g. psychiatric comorbidities and social issues


What were the three main aims of the ICCAM study?

1) Identify neural markers of addiction as targets for treatment and relapse prevention
2) Identify core behavioural components of reward, impulsivity, and emotion underlying relapse
3) Study novel compounds targeting dopamine, opioid, and neurokinin receptors to prevent addiction relapse


State some challenges faced by the ICCAM study

Recruitment, retention,loss to follow-up, comorbidities, social issues, multiple dependencies


State some strengths of the ICCAM study

Double-blinding, placebo control, cross-over design (increased power), multi-faceted data, multi-centre involvement fir faster recruitment


State some limitations of the ICCAM study

Pseudo-randomisation creating possible learning effects, applicability of data from abstinent users, only a single dose of each drug given, potential false positives from multi-dimensional data


ICCAM: Describe the differences in personality measures between the polydrug dependent group, alcohol dependent group, and controls

Both dependent groups had higher scores on measures of depression, anxiety, and impulsivity (none had clinically diagnosed depression or anxiety), as well as more urgency and perseverance. Polydrug dependent individuals were significantly more attention seeking


ICCAM: Describe the differences in spatial working memory between the polydrug group, alcohol group, and control group

The alcohol-dependent group had impaired spatial working memory compared to both others -interesting as most polydrug addicts were also alcoholics. This impairment took the form of more time taken to complete tasks, rather than more errors, possibly due to use of different brain networks to compensate for deficiencies


How could alcohol impair spatial working memory?

It causes hippocampal atrophy


ICCAM: Describe the differences in Cambridge Gamble Task performance between the polydrug group, alcohol group, and control group

Both addicted groups took longer than healthy controls to make a decision. The polydrug group made significantly worse choices and were less sensitive to the probability of winning money


Name the 3 parts of an fMRI paradigm

Preliminaries, functionals, and structurals