Time Course of Dual-task Interference in the Brain in Simulated Driving Environment

Due to the brains limited cognitive capacity, simultaneous execution of multiple tasks can lead to performance impairments, mainly when the tasks occur closely in time. This limitation is known as dual-task interference. We aimed to investigate the time course of this phenomenon in the brain, utilizing a combination of EEG, multivariate pattern analysis (MVPA), and drift-diffusion modeling (DDM). Here, participants first performed a tone discrimination task, followed by a lane-change task with either short or long onset time differences (Stimulus Onset Asynchrony, SOA), in a simulated driving environment. As expected, the dual-task interference increased the second tasks (lane-change) reaction time. The DDM analysis indicated that this increase was attributable to changes in both the decision time and the post-decision time. Our MVPA findings revealed a decrease in decoding accuracy for the lane-change task in short SOA compared to both long SOA and single-task conditions throughout the trial, highlighting the presence of interference. Moreover, the temporal generalization analysis identified a significant interference effect in short SOA compared to long SOA and single-task conditions after [~]250 ms relative to stimulus onset. Additionally, the conditional generalization analysis showed a delayed response after [~]450 ms. Searchlight analysis illustrated the progression of this information reduction, starting in occipital, parietal, and parieto-occipital leads responsible for perceptual and central processing and then transferring to the frontal leads for mapping decisions onto motor actions. Consistent with the hybrid dual-task interference theory, our results suggest that the processing of the two tasks occurs in a partial parallel manner for the first few hundred milliseconds and primarily in the perceptual and decision-processing stages. Subsequently, another competition arises between the two tasks to route information to motor areas for execution, resulting in the second tasks serial processing and delay or lengthening.