| Depression mainly characterized by in low spirits, thinking slow, activity decline and some somatic symptoms, and it is one of the most important factors and frequent problems of human psychiatric disorders. According to prediction of the World Health Organization that depression will become the second largest factor which cause of death and disability throughout the world by 2020. Therefore, experts in psychiatry, psychology, sociology and scholars have been concerned about depression seriously, and systematically studied it from different aspects of depression, in which cognitive mechanism is one of the common focused issues.Previous evidences showed that depressive individuals had widespread executive dysfunctions, including deficits in switching, inhibition and updating processes. But the studies of excutive control were mainly focused on inhibition deficits and information update, relatively small on the impairment of switching. The evidences about depression-related difficulties in switching were collected with Wisconsin card sort Test (WCST), and WCST involved many different processes, making it difficult to separate primary functional deficits, so more studies are needed to clarify this issue with stricter cognitive controlled paradigm. It is necessary to adopt more rigorous cognitive paradigms to research the characteristics of switching impairment of the depression individuals. In this study, we adopted the attentional focus switch paradigm that used in Garavan (1998) and the cue-target task switch paradigm that used in Meiran (2000). Both the two experimental paradigms can control the psychological processes well except switching, so that the index of switching cost could reflect the ability of switching more purely. But there were no studies to explore the impairment of depression with these cognitive paradigms yet. In the present study, we used the behavior and ERP techniques to reveal the mechanism of switching impairment for depressive symptom individual by comparing the switch costs of reaction time and ERP waves with health individuals. The present study was consist of three experiments, the first experiment and the second experiment adopted the attentional focus switching task which required the participants switched their attentional focus within or between phonological loop and visuospatial sketchpad. the third experiment was task switching task in which required the participants to judge a digit with small-large task or odd-even task according to a cue. Overall the results were as follows:1. The depressive symptom individuals had worse performance only in the condition of switching within visuospatial sketchpad than health individuals, but no differences between groups in the condition of switching within phonological loop or between phonological loop-visuospatial sketchpad.2. The difference of N2 component between switching trials and repeated trials was greater for health individuals than depressive symptom individuals only in the condition of switching within visual-spatial sketchpad, but no differences between groups in the condition of switching within phonological loop or between phonological loop-visuospatial sketchpad.3. The difference wave elicited by switched and repeated trials were significant increased in health individuals when the cue-target interval was increased from 500 ms to 1000 ms, but it did not show this results pattern in depressive symptom individuals. The N2 elicited by target in switched trials relative to repeated trials were smaller for depressive symptom individuals than health individuals.The present research suggested that there are special impairments in attentional focus switching function for depressive symptom individuals, mainly exists in switching attentional focus within visuospatial sketchpad. In task switching task, the depressive symptom individuals also had deficit in ability of endogenous preparing in switch based on cue offered the information and in ability of switch to new task set based on target offered exogenous information.
|
PDF Full Text Request