Development of Sensitive Behavioral Assays
NARC modified the semantic fluency test, a classical neuropsychological measure of executive/PFC brain function, to include drug-related categories so as to increase its sensitivity and ecological validity in the study of drug use disorders (Goldstein et al., 2007; Goldstein et al., 2009).
This task was developed for fMRI. Instead of color words (classical Color-Word Stroop task), this task uses drug-related words and matched neutral (e.g., household) words. The individual is required to press a button for an unrelated dimension of the task (word color), allowing us to study the implicit impact on behavior and brain function of word salience (Goldstein et al., 2007; Goldstein et al., 2009).
Using this questionnaire we can distinguish between drug-related liking vs. wanting in cocaine addicted individuals as compared to similar ratings for other primary reinforcers (e.g., food) and correlated with age of cocaine use onset (Goldstein et al., 2010).
Simulated Drug Choice Tasks
NARC developed two neuropsychological drug choice tasks to objectively determine preference for viewing drug-related pictures in cocaine addiction, modeling the classical and highly robust drug-seeking paradigms used in animal studies. Choice to view drug-related pictures as compared to choice to view standardized pleasant, unpleasant, and neutral pictures is indicated by button press. These tasks can be safely administered to abstinent and treatment-seeking individuals. In our ‘explicit’ task, choice is made between two fully-visible side-by-side images; in our ‘probabilistic’ task, choice is made between pictures hidden under flipped-over cards. These tasks have now been validated in their ability to predict highly relevant drug-related outcomes in addiction. Higher drug-related choice is associated with higher actual drug use, measured both concurrently (Moeller et al., 2009) and prospectively (Moeller et al., 2013). In addition, lower drug-related choice tracks improvements at 6-months follow-up in fMRI midbrain functioning (Moeller et al., 2012).
A second function of these simulated drug choice tasks is to interrogate the novel hypothesis of impaired insight in addiction (Goldstein et al., 2009). We defined impaired insight as compromised self-awareness of ongoing choice behavior, specifically the inability to correctly report which types of pictures (pleasant, unpleasant, neutral, cocaine) were chosen for viewing most often (Moeller et al., 2010). Our results have called into question the ubiquitous use of self-reported craving in addiction calling for more objective measures for behavior prediction, such as scalp-recorded ERPs (Moeller et al., 2012). Current research on this topic is exploring the neural correlates of impaired insight as measured with fMRI and voxel-based morphometry (VBM), which have indicated a potentially important role for the rostral anterior cingulate cortex (rACC) (Moeller et al., in press)..
These novel neuropsychological tasks highlight the importance of developing cue-sensitive tasks for probing the neurobiology underlying the particular functional (cognitive-emotional) changes in addicted individuals.
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