The fluctuations of neural activity that mediate neuroadaptations [10] can alter dynamically the cerebral blood flow and volume [11] and produce synchronous magnetic resonance imaging (MRI) signals in different brain regions [12]. This synchronous MRI signal fluctuations have been used to assess the in-vivo functional connectivity of the human brain in resting-state conditions [13]. Here we studied the correlation between signals in midbrain, which is where dopamine (DA) neurons are located, and those in cortical and subcortical structures during sustained attention conditions as a way to assess the modulatory strength of the dopaminergic pathway on cognition in cocaine addiction. We used a sustained attention drug-word (DW) task that tests the processing of drug vs. matched neutral words [14]. Using this DW task we showed that compared to controls cocaine addicts had higher drug-cue related activation in midbrain [15], and hypo-activation in anterior cingulate cortex [16]. Based on our previous findings [2], [15]–[18] and preclinical studies documenting disruption of dopaminergic pathways with repeated cocaine administration [19], [20], we hypothesized that hypoactive brain regions in cocaine abusers would also show lower functional connectivity with midbrain.
