Prefrontal cortex plays an important role in decision making (DM), supporting choices
in the ordinary uncertainty of everyday life. To assess DM in an unpredictable situation,
a playing card task, such as the Iowa Gambling Task (IGT), has been proposed. This
task is supposed to specifically test emotion-based learning, linked to the integrity of
the ventromedial prefrontal cortex (VMPFC). However, the dorsolateral prefrontal cortex
(DLPFC) has demonstrated a role in IGT performance too. Our aim was to study, by
multichannel near-infrared spectroscopy, the contribution of DLPFC to the IGT execution
over time. We tested the hypothesis that low and high risk choices would differentially
activate DLPFC, as IGT execution progressed. We enrolled 11 healthy adults. To identify
DLPFC activation associated with IGT choices, we compared regional differences in
oxy-hemoglobin variation, from baseline to the event. The time course of task execution
was divided in four periods, each one consisting of 25 choices, and DLPFC activation was
distinctly analyzed for low and high risk choices in each period. We found different time
courses in DLPFC activation, associated with low or high risk choices. During the first
period, a significant DLPFC activation emerged with low risk choices, whereas, during
the second period, we found a cortical activation with high risk choices. Then, DLPFC
activation decreased to non-significant levels during the third and fourth period. This study
shows that DLPFC involvement in IGT execution is differentiated over time and according
to choice risk level. DLPFC is activated only in the first half of the task, earlier by low
risk and later by high risk choices. We speculate that DLPFC may sustain initial and more
cognitive functions, such as attention shifting and response inhibition. The lack of DLPFC
activation, as the task progresses, may be due to VMPFC activation, not detectable by
fNIRS, which takes over the IGT execution in its second half.
