A method recently proposed for studies based on blocked fMRI datasets [32] was used to evaluate the functional connectivity of the brain using the resting epochs. Here, we were interested in the functional connectivity of the midbrain during the performance of the sustained attention condition of the drug-word task, not during resting-conditions. The task design was advantageous for this purpose because the “word” epochs were 70 seconds long, almost double the length of the resting blocks used by Fair and colleagues. In order to minimize unwanted task-related effects on the strength of correlations with midbrain (CM) we discarded 11 seconds from each word epoch, using the canonic hemodynamic response function to optimally select time points of the word epochs. Specifically, for each time series, the plateaus of the SPM2 canonic hemodynamic response function (Fig. 2A, red curve) were used to identify the 37 consecutive time points of the plateaus (Fig. 2B green and blue curves) corresponding to “word” epochs. This procedure accounted for the initial delay of the hemodynamic response and its return to baseline. The selected time points corresponding
