Objective: Cue-induced craving is central to addictive disorders. Most cue-reactivity fMRI studies are analysed statically and report averaged signals, disregarding the dynamic nature of craving and task fatigue.
Methods: Thirty-two early abstinent methamphetamine users underwent fMRI-scanning while viewing visual methamphetamine cues. A Craving>Neutral contrast was obtained in regions of interest. To explore changes over time, the pre-processed signal was divided into three intervals. Contrast estimates were calculated within each interval, and were compared using ANOVA followed by post hoc t-tests. The results were compared with those from a static analysis across all blocks.
Results: A priori expected activations in the prefrontal cortex, insula and striatum not detected by static analysis were discovered by the dynamic analysis. Post hoc tests revealed distinct temporal activation patterns in several regions. Most showed rapid activation (including both ventral/dorsal striata and most regions in the prefrontal, insular and cingulate cortices) whereas some had delayed activation (the right anterior insula, left middle frontal gyrus, and left dorsal anterior cingulate cortex).
Conclusions: This study provides preliminary insights into the temporal dynamicity of cue-reactivity, and the potential of a conventional blocked-design task to consider it using a simple dynamic analysis. We highlight regional activations that were only uncovered by a dynamic analysis, and discuss the interesting and theoretically expected early versus late regional activation patterns. Rapidly activated regions are mostly those involved in the earlier stages of cue-reactivity, while regions with later activation participate in cognitive functions relevant later, such as reappraisal, interoception and executive control.