Measuring Individual Stress Responses Based On CDA: A Method For Multivariate Decoding

Acute stress refers to the body’s non-specific response when the load exceeds the body’s ability to regulate,which will have a significant impact on the executive control area of the brain,and multiple cognitive functions including working memory will be affected.Working memory refers to the memory system that temporarily processes and stores information,and its capacity is limited.Contralateral delayed activity(CDA)is an index that reflects the capacity of visual working memory.While traditional univariate ERP methods fail to detect subtle aspects of neural representations,multivariate pattern classification(decoding)methods are commonly used to study cognitive neural processing in typical individuals,and they can be used to quantify the information present in an individual’s neural signals.Based on this,this study uses event-related potential technology and multivariate decoding method to explore(1)the impact of acute stress on individual working memory ability;(2)whether multivariate decoding method can be used to compare stress groups and ordinary people Neural representation.In this study,40 healthy adult subjects were recruited,divided into control group(20 persons)and stress group(20 persons),half male and half male.The experiment adopts a 2(group: stress group,control group)× 3(memory load: 1,3,5)mixed experimental design,in which the group is a variable between subjects.The acute stress response of the stress group was induced by the Maastricht acute stress test technique;the change detection task was used to measure the working memory of the subjects,and the EEG signals of the subjects were recorded during the task.First,univariate analysis was performed on salivary cortisol level,positive and negative mood scale scores,state anxiety scale scores,reaction time,correct rate,memory capacity and CDA amplitude,and then support vector machines(Support Vector Machines,SVM)and The combined model of Error-Correcting Output Codes(ECOC)decodes the collected EEG data.The results showed that:(1)The acute stress task successfully induced the acute stress response of the subjects,the salivary cortisol level of the stress group was significantly higher than that of the control group,the scores of negative emotion and state anxiety were also higher,and the scores of positive emotion is lower.(2)In the change detection task,the response time of the stress group was longer,the correct rate was lower,and the working memory capacity was lower than that of the control group.(3)The permutation test on the CDA components from 400 ms to 1000 ms found that: on load 1 and 5,the CDA of the stress group was significantly smaller than that of the control group,and there was no significant difference on load 3.(4)The results of multivariate decoding analysis showed that under all loads,the correct rate of decoding in the control group was greater than that in the stress group.To sum up,the following conclusions can be drawn:(1)Acute stress can reduce the individual’s working memory ability.(2)Multivariate decoding methods can be effectively used to compare the neural representations of stressed and non-stressed people.Multivariate decoding methods can be effectively applied at the individual subject level to understand the nature of cognitive impairment in stressed populations.