Switching Process Erp Study

Task switching is the basic way in human' cognitive activities, and the switching process is an important aspect of executive control. It was presented as controlling switching course between two tasks which compete the same cognitive resources in working memory. Switching costs refer to longer reaction times (RT) on task switch trials(e.g. AB) compared to task-repeat trials(e.g. AA) It is an indicator of executive control. In this paper, we resrarch the neurophysiological mechanisms of task switch in foreknowledge and no-foreknowledge by two behavioral experiments and two event-related potentials experiments.A "task-swich" paradigm was used in this study. Tasks consisted in a simple classification of Chinese words (noun/verb) or digits (odd/even). Particicants porformed two tasks which are repeated (e.g. AA, BB...) or swihched (e.g.. AB, BA...), There are two continued tasks in each tial(task one and task two). The task one in repeat trials and switching trials (e.g. AA and AB), and the task two in repeat trials and switching trials (e.g. AA and AB) were analysed and compared separately.Thirty undergraduates particicants joined the two behavioral experiments, and other seventeen undergraduates joined the two event-related potentials experiments.As the results of two behavioral experiments: there are significant switching costs in digit tasks and word tasks in foreknowledge and no-foreknowledge; In task one , the RTs of digits in switching trials are longer than repeated trials under foreknowledge, so as words.The behavioral results from ERP experiments are similar to the results of behavioral experiments. In task one, there's a more larger negative going wave in switching trials compare to repeat trials under foreknowledge, and the latency was at about 330ms; A larger late negative going slow wave evoked by switching trials in 500~800ms; The repeat tasks evoked a larger positive (alike P3b) than switching tasks. Under no-foreknowledge condition, also a more larger negative going wave with the latency of about 330ms in switching trials compare to repeat trials, and repeat tasks evoked a larger positive (alike P3b) than switching tasks. The cerebral regions to do work for digits and words are different.These results suggest: swiching cost is a special phenomena with task swith; Swiching process involves endogenous preparation and exogenous adjustmentn under foreknowledge, butonly exogenous adjustmentn under no-foreknowledge. Actually, the endogenous preparation and exogenous adjustmentn are same procedure of cognitve conflict; The larger positive (alike P3b) perhaps reflect the difference of frequency which events appear; The endogenous preparation starts after the presence of stimulus for task one, not after the accomplish response to task one; There's a mater-specific in task switching.