Pattern Change of Inhibitory Drug Craving Control in Brain: A Study of Effective Connectivity

Abstract

Background: The inhibitory behavioral control of brain in treated drug abusers encountering drug cues, as well as the constructing regions of its network, has been widely studied previously. The causal relation of relevant brain regions has also been noticed in the literature, but the time/task condition variability of this causal network has not been studied yet.Method: Thirteen drug abusers successfully treated with Methadone maintenance therapy, were scanned during a drug cue fMRI task. Two regions of interest (VMPFC and amygdala) were chosen based on the literature. Using Dynamic Causal Modelling (DCM), an effective connectivity network was estimated between these two brain regions and a craving-inducing input. Later, implementing a sliding window method on the extracted time-series, five further DCM networks were estimated to evaluate the time variability of the DCM network.Results: The result of ordinary DCM showed that there were reciprocal connections between regions, and the craving input only affects the amygdala region. Sliding window showed that the input link strength changes during the task. This change was an exponential growth which moved from near zero to a positive value.Discussion: The pattern of our DCM network demonstrated that the craving input passes from bottom brain regions to the top, and therefore, it indirectly affects top regions. However, the causal relations of this network varies during the task, and the craving link strength also grows exponentially. Our findings are in agreement with the hypothesis of craving inducement during stimulation, and therefore it may be considered as a proxy craving measurement.