Effects of switching between neutral and emotional stimuli: An ERP study on switch cost

To investigate if switch cost involved in shifting between neutral and emotional stimuli is reflected by ERPs correlates. The subjects were 14 healthy right-handed college students (7 females, 7 males). Caravan's (1998) task paradigm which was important in studying inner attention shifting was used. The subjects were asked to watch a stimulus sequence comprising Schematic line drawings of faces with neutral and emotional expressions, and make counts of them (neutral faces or emotional faces). EEG signals were recorded at 64 sites. 1) Switching between stimuli elicited slow responses, increased N₂ amplitudes and reduced P300 amplitudes. 2) A negative component (Nd370) was found when ERP wave during non-switching trials was subtracted from that during switching trials, and it was found obviously at extensive parietal area. 3) Nd370 amplitude during switching from emotional stimuli to neutral ones was smaller than that during switching from neutral stimuli to emotional ones. Nd370 can be taken as an index of switch cost effect.