Abstract
BackgroundWhen switching from one task to a new one, reaction times are prolonged. This phenomenon is called switch cost (SC). Researchers have recently used several kinds of task-switching paradigms to uncover neural mechanisms underlying the SC. Task-set reconfiguration and passive dissipation of a previously relevant task-set have been reported to contribute to the cost of task switching.Methodology/Principal FindingsAn unpredictable cued task-switching paradigm was used, during which subjects were instructed to switch between a color and an orientation discrimination task. Electroencephalography (EEG) and behavioral measures were recorded in 14 subjects. Response-stimulus interval (RSI) and cue-stimulus interval (CSI) were manipulated with short and long intervals, respectively. Switch trials delayed reaction times (RTs) and increased error rates compared with repeat trials. The SC of RTs was smaller in the long CSI condition. For cue-locked waveforms, switch trials generated a larger parietal positive event-related potential (ERP), and a larger slow parietal positivity compared with repeat trials in the short and long CSI condition. Neural SC of cue-related ERP positivity was smaller in the long RSI condition. For stimulus-locked waveforms, a larger switch-related central negative ERP component was observed, and the neural SC of the ERP negativity was smaller in the long CSI. Results of standardized low resolution electromagnetic tomography (sLORETA) for both ERP positivity and negativity showed that switch trials evoked larger activation than repeat trials in dorsolateral prefrontal cortex (DLPFC) and posterior parietal cortex (PPC).Conclusions/SignificanceThe results provide evidence that both RSI and CSI modulate the neural activities in the process of task-switching, but that these have a differential role during task-set reconfiguration and passive dissipation of a previously relevant task-set.
Highlights
Executive control is an endogenous process necessary for performing various tasks in parallel, so that we are able to flexibly coordinate several processes at a time in order to accomplish a particular plan or goal [1,2]
reaction times (RTs), in which long cue-stimulus interval (CSI) resulted in a significant decrease in switch cost (SC) of RTs (p,0.001), but no such effect was present for Response-stimulus interval (RSI) condition
There was a main effect of CSI condition for SC of error rates (p,0.05) with lower SC overall in the long CSI condition, but no such effect was present for RSI condition
Summary
Executive control is an endogenous process necessary for performing various tasks in parallel, so that we are able to flexibly coordinate several processes at a time in order to accomplish a particular plan or goal [1,2]. When switching from one task to another new task, reaction time becomes longer and error rates increase, a phenomenon known as switch cost [6,7,8]. First one is the taskset inertia (TSI) theory suggesting that the SC reflects a passive dissipation process from the previous task [7]. A new study challenged these traditional theories and reported that SC reflects an adaptation process to the abstract task representations by a parametric approach [9]. When switching from one task to a new one, reaction times are prolonged This phenomenon is called switch cost (SC). Researchers have recently used several kinds of task-switching paradigms to uncover neural mechanisms underlying the SC. Task-set reconfiguration and passive dissipation of a previously relevant task-set have been reported to contribute to the cost of task switching
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