How acute stress alters cognitive flexibility
function? The electrophysiological evidences
Caihong Jiang a, Pei-Luen Patrick Rau a, *
a Institute of Human Factors and Ergonomics, Department of Industrial Engineering, Tsinghua University, Beijing, China, 100-084
全国信息公示系统官网ABSTRACT
Drivers must be able to focus on the real-time information of the traffic environment and make suitable changes according to the information received while driving. This process involves in an important cognitive function -cognitive flexibility, which is defined as the ability to modify previously behavior following changes that alter the outcome of that behavior. However, this ability may be easily altered when expod to acute stress, especially for novice drivers. The literature regarding how acute stress influences cognitive flexibility function and the underlying cognitive neural mechanism in novice driver are scarce. Due to the high time resolution, the prent study aimed to adopt the event-related potentials (ERPs) to explore the answer to this question. A total of 39 healthy
novice drivers were recruited to participate our experiment. They were required to conduct a task-switching task under stress or control conditions, which were induced by the Trier Social Stress Task (TSST) or control procedure. Positive affect and negative affect schedule (PANAS) was ud to asss stress reactivity throughout the experiment. The results showed that a higher negative affect in the stress condition compared to the control condition, indicating a successful stress induction. The behavioral results showed that the stress group had a trend for longer respon time than the control group. The ERP results revealed that the control group had a reduce P1 and less positive N1 amplitude in the switch trials than the non-switch trials, but this effect was missing in the stress group. The results indicated that acute stress impaired cognitive flexibility function both on the behavioral performance and cognitive neural mechanism. This study contributed to the expanding theoretical ba of understanding the cognitive neural mechanism behind acute stress influencing cognitive flexibility. The findings also have implications for the safe driving habits of novice drivers and for traffic administrators when deciding the responsibility for traffic accidents.
Keywords: Acute stress, Cognitive flexibility, Task switching paradigm, Event related potentials一个月来两次
1.Introduction
Novice drivers have proved to be overreprented in road crashes (Mayhew, Simpson, & Pak, 2003). A lot of factors were related to the high accident involvement in young novice drivers, including brain immaturity, unskilled driving, driving skill, poverty of driving experience, more risk taking and so on (Mytton, Towner, Brussoni, & Gray, 2009; Paus, 2005; Ulleberg & Rundmo, 2003). But a vital factor-executive function-has less chance to come into the picture. Driving is a complex, goal-oriented task that require drivers to focus on the real-time information of the traffic environment and make suitable changes according to the information received while driving. This process cannot succeed without the cognitive flexibility involvement, which is defined as the ability to modify previously behavior following changes that alter the outcome of that behavior (Graybeal, Kilycznyk, & Holmes, 2012). Using a driving simulator, Mantyla, Karlsson, & Marklund (2009) found that novice drivers with a low performance in cognitive flexibility had a poor driving performance in driving tasks.
As we know, cognitive flexibility can be easily altered when expod to acute stress, in which context, young novice drivers are more prone to involve in car accidents (Lee & Winston, 2016). Existing few behavioral rearches display relatively consistent outcomes showing impaired influence of cognitive flexibility under acute stress (Plessow, Kiel, & Kirschbaum, 2012;
Starcke, Wien, Trotzke, & Brand, 2016). However, behavioral results cannot tell us the intermediate process from the stimulus input to the behavioral outcomes output. How and at which stages acute stress impact cognitive flexibility in novice drivers is still unknown. With high time resolution, event-related potentials (ERP) are possible to examine the underlying cognitive neural process occurring in the brain following acute stress. Thus, this study aimed to explore the intermediate neural process of cognitive flexibility after acute stress in novice drivers with ERP and behavioral methods.
2. Methods补录志愿
2.1 Participants
Thirty-nine healthy novice drivers with less than 1 year of driving experience took part in our experiment. All of them had a valid driver’s licen and normal or corrected-to-normal vision. Participants were allocated into acute stress or control contexts by random. Four participants were excluded from the final analysis becau of the low accuracy or mechanical disorder. Finally, the control group had 17 participants (female, 8;
22.47 ± 2.67 years), and the stress group had 18 participants (female, 8; 21.22 ± 2.05 years). The tw
o groups did not differ in gender, age, education level, and driving experience. This study was approved by ethical review.
无线速率2.2 Procedure
Participants rested for 15min after they arrived at the lab. Then, they received the stress treatments which were elicited by a modified Trier Social Stress Test (TSST; Buchanan, Bagley, Stansfield, & Preston, 2012) and control task (Buchanan, Laures-Gore, & Duff, 2014). In the TSST task, participants need to justify themlves for being accud of stealing before three store managers and then do a backward subtraction. The participants in control context just need to generalize the main idea of a plain travel passage and do simple written mathematical operations. Both the stress and control treatments lasted for 15min. Then, participants were told to perform the task-switching task and EEG recorded at the same time. Positive affect and negative affect schedule (PANAS) were measured at after rest, 0 min, 15 min, and 30 min after the end of stress treatments to evaluate the stress reactivity. 2.3 Task-switching paradigm
In this task, each trial had a cue and a stimulus.
A square and a rhombus were adopted as cues and the stimuli was compod of 9 digits (from 1 to
9). Each trail started with a cue with a duration for 1000 ms which specified the required task. When the cue was a square, participants had to judge whether the following digit was greater or less than 5. When the cue was a rhombus, participants had to judge whether the following digit was odd or even. A cue-target interval (CTI) with black screen appeared for either 200 ms or 1000 ms between cue and stimulus. The trial ended as soon as a respon was made and a maximum respon time was 3600 ms. A trial-interval-trial (TIT; 1000 ms) was paired with a short CTI (200ms) while a short TIT (200 ms) was paired with a long CTI (1000 ms) in order to keep a constant interval between the respon and the new stimulus. If the current trial had the same cue as the trial before, the current trial was classified as ‘non-switch’; if there was a cue change, the trial was classified as a ‘switch’ trial. Greater reaction times and higher error rates in switch trials than non-switch trials were classified as switch cost.
2.4 EEG recording and processing
The 64 Ag-AgCl electrodes arranged according to a standard 10-20 system were ud to record electroencephalogram (EEG). All EEG electrodes were referenced online to an electrode at left mastoid, and referenced off-line against the average of left and right mastoids. The electro-oculogram were recorded from electrodes placed at the outer canthi of both eyes and below and abo
ve the left eye. Signals were amplified with a high and low pass filter t at 0.05 and 100 Hz, respectively, and digitized at 1000 Hz. The impedance was kept below 5 kΩ. EEG data was analyzed by the Neuroscan Curry 7.0 software with a low pass filter of 30 Hz. EEG gments were extracted from 100 ms before to 600 ms after stimulus prentation, and trials containing activity exceeding ±100 µV were automatically detected and rejected. Ultimately, the grand average ERPs were formed by averaging trials according to different conditions.
3. Results
3.1 Subjective measures
Repeated analysis of variance (ANOV A) were
performed on PANAS scores with the factors of group and time. For negative affect, the group by time interaction was significant, F(3, 99)=11.11, p<.001, η2=.25. Further analysis showed that the stress group did not differ from the control group at baline measurements, but the stress group had more negative affect than the control group at post-TSST 0 min (p<.001), 15 min (p<.01), and 30 min (p<.05; e Figure 1). The main effect for time,F(2.44,80.54)=6.46, p<.01, η2=.16, and group were significant, F(1,33)=11.49, p<.01, η2 =.26. For positive affect, the time main effect, [F (2.41,79.
49)=77.82, p<.001, η2 =.70] and group by time interaction effect were significant, F(3,99) =2.78, p<.05, η2=.08. Further analysis showed that the stress group had marginally less positive affect at post-TSST 0 min (p = 0.06; e Figure 1).
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3.2 Behavioral results
Repeated ANOVAs were performed on reaction times (RTs) and accuracy parately with the factors of group, switching and CTI. RTs less than 200ms or greater than 1500ms, as well as RTs exceeding 3 standard deviations, were excluded. For RT, the main effects for switching [F(1,33)=62.61, p<.001, η2=.66] and CTI [F(1,33) =37.09, p<.001, η2=.53] were significant. Switch trials had longer RT (776ms) than non-switch trials (698ms) and the short CTI (762ms) had longer RT than the long CTI (712ms). The significant switch by CTI interaction was mainly driven by switching main effect, F(1,33)=6.53, p <.05, η2=.17. There was marginally significant group difference, F(1,33)=3.42, p=.07, η2=.09, indicating that the stress group (774ms) had a slower respon than the control group (700ms, e Figure 2A), suggesting delayed respon speed of switch ability following acute stress. For the error rate, the results showed that the main effects for switching [F(1,33)=36.79, p <.001, η2=.53] and CTI [F(1, 33) = 33.53, p < .001,η2=.50] were significant. The CTI by switch interaction was significant, F(1, 33)=9.07, p < .01, η2=.22, indicating that switch trials (11.7%) had a
蚂蚁的特征higher error rate than non-switch trials only in the short CTI (6.3%; e Figure 2B). The group by switching interaction was marginally significant, F (1, 33)=.28, p =.08, η2=.09, and further analysis showed that the interaction was mainly driven by switching main effect, indicating that the switch trials had more error rates than non-switch trials both in the long and short CTI conditions.
3.3 ERP results
Both P1 and N1 components were measured at PO5/6/7/8 electrode sites and repeated ANOVAs were conducted on P1 and N1 with the factors of group, switching, site and hemisphere parately. P1: For P1 amplitude, the switching main effect was significant, F(1,33)=4.66, p<.05, η2 =.12, switch trials (3.77μV) had smaller P1 than non-switch trials (3.86μV). The interaction of group by switching by CTI by site, the interaction of group by switching by CTI by hemisphere were significant (ps<.05) and the group by CTI interaction was marginally significant (p=.07), but no significant effects were found in the further analysis of the interactions. Although the interaction of group by switch was nonsignificant, F(1, 33)=2.55, p= 0.12, η2=.07, post hoc test was also performed on the interaction bad on the results of previous studies. The results showed that the control group had a reduced P1 amplitude in the switch trials (3.26μV) than non-switch trials (5.20μV), F(1, 33) =6.09, p<.05, η2=.16, while this effect was missing in the stress group (e Figure 3). For P1 latency, the CTI main
effect was significant, F(1,33)=7.30, p<.05, η2=.18, showing that P1 peaked earlier in the long CTI than short CTI. The interaction of hemisphere by CTI was significant,F(1,33) =11.35, p<.01, η2 =.26. Further analysis indicated that the earlier P1 in the long CTI only occurred in the right hemisphere (long: 96ms; short: 106ms) relative to
the left hemisphere (long: 108ms; short: 108ms).
N1: For N1 amplitude, the interaction of group by switching by CTI by site was significant, F(1, 33)=5.62, p<.05, η2=.15, but further analysis did not find any significant effects. The group by switch interaction was not significant, F(1,33)= 2.11, p=0.16, η2= .06. However, the post hoc test showed that the control group had larger N1 in the switch trials (-6.81μV) than non-switch trials (-4.96μV), F(1, 33) =4.96, p<.05, η2=.13, and this effect also disappeared in the stress group (switch: -6.29μV;
non-switch: -6.12μV; e Figure 3). For N1 latency, the CTI main effect was significant, F(1,33)=43.14, p <.001, η2=.57, indicating that the long CTI (158ms) elicited an earlier N1 amplitude than short CTI (168 ms). The CTI by hemisphere by switch interaction was significant, F(1,33)= 6.82, p< .05, η2=.17, and further analysis showed that the interaction was mainly driven by CTI effect.
实习项目The disappeared switching effect in the ERP results in the stress group suggested that acute stress disrupted switch ability on the neural level.
4. Conclusion
The current study found that acute stress impaired novice drivers’ cognitive flexibility both on the behavioral performance and cognitive neural mechanism.
Acknowledgment
This study was funded by the State Key Lab of Automobile Safety and Energy and a National Natural Science Foundation China grant 71661167006.
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湖南地名
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