Different Brain Activation Of Switching Costs And Mixing Cost In Task Switching

Typically,in task-switching contexts individuals are slower and less accurate when repeating a task in mixing blocks compared to single-task blocks(mixing cost)and when switching to a new task compared to repeating a previous one(switch cost).Previous event-related potential(ERP)studies have identified the neural mechanism of switch cost in cued task-switching paradigms,and there also have a few researches focused on mixing cost.However,it is not yet completely clear electrophysiological correlates underlie the two different costs.In order to get a better understanding of neural mechanism between the switch costs and mixing costs,we examined electrophysiological mechanisms and brain activation differences between two costs using the event-related potentials(ERPs)by the cued task-switching paradigm.There are three experiments in this research,and task was number task or letter task,which means individuals need to judge the odd-even of number or Vowel-Consonant of letter according to the cue.In order to explore the characteristics of cognitive processing in switch cost and mixing cost,the type of block was designed as previous researches in the first experiment,which includes a mixing block and single block.The cue of single trial was changed and only mix block was existed in the second experiment.Through the comparisons between different trial types,the influence of cue-set to switching cost and mixing cost may be found.The third experiment was on the basis of the second experiment,but there are also a small adjustment in the cue-set of single trials.In this experiment,event-related potentials was used to explore the evoked potential in different trial types so that more characteristics of cognitive processing in switch cost and mixing cost could be known and understood.Specific results are as follows:(1)The results of experiment 1 showed that there are no significant difference between the number task and the letter task,the switch cost and mixing cost were existed.However,the mixing cost was larger than switch cost in two tasks and the difference of two costs in letter task was less than number task.(2)The experiment 2 found that,the switch cost and mixing cost also were existed while the cue was changed in single trial,but the mixing cost reduced significantly compared to experiment one and the switch cost was unchanged.(3)The behavioral results of the experiment 3 was consistent with the experiment 2 and both of the switch cost and mixing cost were existed,but switch cost and mixing cost have no difference significantly in two tasks.The electrophysiological results shown that there are three components in cue-locked,which included frontal N1?P2 and P3.The mixing cost was found in those components,which means repeat trial evoking larger amplitude than single trial.But in contrast to the result of reaction time,there are some invert results in ERP correlate of switch costs,which means repeat trial evoking larger amplitude than switch trial in frontal N1 and P2.In target-locked,there have four components were found,which included P1?N1?P2 and P3 b.The mixing cost was found in N1 and P2,while switch cost was found in P1.There also some inverted was found,which means single trial evoking larger amplitude than repeat trial in P1 and repeat trial evoking larger amplitude than switch trial in N1 and P2.Moreover,the ERP switch cost also was reflected in a reduced parietal P3 b,and the result is consistent with previous researches.