fMRI and the Neurobiology of Addiction Flashcards
Understand the underlying complexity of addiction disorders Understand the use of fMRI to study addiction disorders Understand the use of fMRI in medication development for addiction disorders Describe an example design of a multi-centre neuroimaging study, including its aims and objectives in addressing the problem of relapse to addiction Evaluate the study's strengths and limitations Describe fMRI tasks used to probe addiction and relapse mechanisms - examples of reward processing, inhibitory
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