An Electrophysiological Study Of The Separability And Plasticity Of Active And Reactive Control Modes In Task Switching

In daily life,as one of the executive functions,the ability of task switching ensure individuals switch various tasks from different requirements as context changes flexibly,which cognitive processes involved in task switching is a popular topic of task switching researches which has proved that task switching require the collaborative participation of different cognitive processes in dynamic periods.The cue-task paradigm divides task switching into two parts by manipulating whether the cues that occur before the switching task provide the information about the upcoming task,namely the preparation part before the task and the post-adjustment part after the task.The first part which is endogenous happens when the cues provide enough information for the upcoming task.Individuals take initiative to change their current goal,allocate cognitive resources to maintain the switching information constantly,and prepare for the upcoming task.The whole process above manifest as retrieving task sets from working memory and deactivate the task sets for previous task.However,when cues cannot provide the task-related information,individuals is not able to obtain the information of switching through varied context.Instead,they can only capture and retrieve the characteristics of the stimulus by recruiting attention resources and inhibit the interference effect brought by irrelevant stimuli when the task appears.These two part of process are considered as the instances of two modes of cognitive control.According to the dual mechanism framework of cognitive control,the preparation process driven by the switching cues corresponds to proactive control,while the post-adjustment process driven by task corresponds to reactive control.Both control modes have similar brain mechanisms,which take the lateral prefrontal cortex(l PFC)in frontal-parietal network as the hub area.When cognitive requirements generate,the l PFC communicates with peripheral brain areas to play synergistic role through neural oscillations in different frequency bands.Among those oscillations,theta(4-7Hz)is the most important one in both cognitive control modes.For the study proactive control and reactive control,few of them aim at distinguish the differences of these two control modes in task switching.Considering that,our study use two methods to separate them.The first one is the working memory capacity that measured in the operation span task.We divide healthy participants as high and low working memory capacity and compare their behavioral performance as well as theERSP through cue-task paradigm to observe the differences between proactive control and reactive control contributed by working memory capacity.In the second one,we apply neurofeedback to healthy participants,which is an noninvasive brain stimulation methods that trian individuals to learn how to self-regulate their own brain activities after may times of training through feedback from generating the changes of target signal in a variety of sensory ways in real-time.We take the theta coherence in frontal-parietal network as the target signal of nerofeedback and instruct participants to up-regulate it.We make this study based on the effect of frontal-parietal theta coherence in both cognitive control modes,and also compare the differences of neurofeedback training effects in two cognitive control modes in cue task paradigm so as to observe which cognitive control modes depends more in theta oscillations.In study 1,we use Bin score that combined the trade off of speed and accuracy as the index of switching cost and calculate the ERSP after time-frequency transform.The results indicated that high working memory capacity group have better performance in proactive control,compared with low working memory capacity group,while there are no significant differences between these two groups in the performance of reactive control.High working memory capacity group shows higher frontal-parietal theta ERSP than low working memory capacity group in two periods of proactive control,one is the period correspond to the switch related information and another correspond to the task related information.These results indicate that proactive control in task switching depend more than reactive control,which may due to more working memory processes participate in proactive control and also mean the individuals with higher working memory has higher retrieval efficiency in proactive control that can improve the performance of task switching.In study 2,the results of neurofeedback training show that both proactive control and reactive control performances get improve after theta coherence neurofeedback.And the performance of reactive control is higher than that in proactive control.The better performance in reactive control means reactive control is more sensitive to theta oscillation in frontal-parietal network,which may due to the reason that the transient but high cognitive load reactive control may require the theta oscillation which is regard as the information communication channel to provide more information in maintaining the effect of reactive control.Hence,the up-regulate theta neurofeedback training improve the performance of reactive control through directly increase the communication information to support reactive control.However,proactive control need lowercognitive load and works in a longer period,which means it require more in stability than density of the theta oscillation.In addition,we also find the positive control group that train to up-regulate the upper alpha coherence in non-frontal-parietal brain areas improve the performance of reactive control.Because the inhibit function that suppress the irrelevant target and corresponding response need wide spread activate of upper alpha oscillation,the results of positive control group may reflect the improvement the inhibit then affect the reactive control indirectly.The results of study 1 and study 2 both show that both proactive control and reactive control can be distinguished by individual characteristics like working memory capacity and non individual characteristic like neurofeedback training of the theta coherence in frontal-parietal network during task switching.