关键词: 认知分心, LPP, 背外侧前额叶皮层(DLPFC), N2, 认知控制

Abstract:

The visual-spatial resource competition theory suggests that the frequency of flashback could be reduced, when a visual task competes with trauma-related negative pictures for the limited space resources. However, the cognitive control theory hold the view that the central executive control system, as the core of the working memory system, compete with trauma-related negative images for the cognitive control ability. And this ability can be reflected by intense cognitive distraction tasks, indexed by N2 and the late positive potential (LPP) at the neural level. However, it is unclear how the intensity of cognitive distraction modulates the neural processing of the trauma-related information. The present event-related potentials (ERP) study used the traumatic film paradigm and improved working memory paradigm to investigate the effect of cognitive distraction’s intensity on the process of trauma-related information. Two parts consisted of the experiment: watching the traumatic film and completing working memory task. Before and after watching the traumatic film, 22 Participants completed PANAS, but the STAI scale was used only before the film. During the working memory task, participants were told to perform a task which requiring to memorize letters at the beginning. Each trial began with a two- or six-letter string presented on a black background for 5, 000 ms. Next, a white fixation cross appeared for 500~1, 000 ms, followed by a trauma-related picture or a unrelated neutral picture in random order for 2,000 ms. Then, the words ‘what were the letters?’ were presented on the screen. In the following, participants pressed the key of ‘Enter’ and typed the letters in the black empty screen in the order they had memorized them. Participants could use the backspace key to correct mistakes. The trial ended when participants pressed the enter key again when they finished typing letters. The trial interval varied randomly from 2,000 to 2,500 ms, during which a white fixation cross was presented on a black background. The EEG was recorded while the picture appeared. Participants then completed PANAS again after the working memory task. The results showed that: (1) the amplitudes of N2 to the high-load task were significantly larger than those of low-load task; (2) the amplitudes of LPP for trauma-related negative pictures were larger than trauma-related neutral and unrelated neutral pictures in the low-load task, whereas there were no significant differences among the three kinds of pictures in the high-load task; (3) for the trauma-related negative pictures, LPP activity was significantly greater to the high-load task than the low-load task. The results of the present study indicated that the cognitive distraction of the high-load task had a stronger modulation to trauma-related information. This provided support for the cognitive control theory.

Key words: cognitive distraction, Late positive potential (LPP), DLPFC, N2, cognitive control