| AIM:Emotion as a psychophysiological procedure contains several stages including receiving, evaluation, subjective experience and expression. Emotion is not spontaneous but evoked by either internal or external events. Emotion has different component including happy, anger, sorrow, fear and other subjective feelings. The debate is continuing on emotion mechanism whether it is automatic process or controlled process.Stroop effect happened when a color word such as GREEN written in red ink, its naming time is longer than that of a neutral word such as CHAIR. There are many theories to explain this effect, a view that reading is highly automatic, but color naming is not. Behavioral emotional Stroop effect has also been reported and it suggested emotional information had impact on color naming. Emotional Stroop task could be used to investigate emotional information processing. Patients with anxiety disorder demonstrated a delay in naming the colors of the threat words, it suggests that high anxiety individual is difficult to ignore the negative information, negative words get more attention resources, and the relative lack of attention resources led to the delay in naming colors. Combined spatiotemporal patterns of event-related potentials (ERPs) with emotional Stroop paradigms, we explore the neural processing mechanism of emotional words in this research. MethodThree categories of words were used: positive, neutral and negative emotional words. Each category contains 30 words with red, yellow, blue, green color print, 360 words in total. Thirteen healthy college students participated, 5 males and 8 females, right-handed, aged 24-28 years (mean 25 years), without family history of mental illness, with normal vision.Duration of each word was 800 ms, showed in the central screen, size of 10.6×12.3 cm~2 with SOA of 1200ms. The subject was seated in an armchair facing a computer screen at a distance of 1.0 m, horizontal and vertical angle was 6.0°, 7.0°with 85 Hz of screen refresh rate.Participants were required to decide whether the font of each word was red/yellow or blue/green by pressing button on a game pad after the target word presentation. The reaction time and accuracy of behavioral response were recorded. Event-related EEG was recorded from 19 channels of international 10-20 system with linked earlobes as reference. EEG epochs from 100 ms before to 900 ms after target stimulus were amplified by means of a ERPs system developed in our lab. Digitized with sampling frequency of 1000 Hz and bandwidth of (0.10, 60) Hz and 50 Hz notch. Electrode impedance during the experiments did not exceed 5 kO. Trials contaminated with ocular, muscular or any other type of artifacts were inspected visually and rejected. Sweeps exceeding±50 microvolt in any of the channels and those with incorrect performance were excluded from the ERP averaging offline. 240 seconds each interval and rest 20 seconds. A practice that consists of 10 words not presented in formal session was arranged before ERP experiment.ANOVA of single factor of repeated-measure with three level (word valence: positive/negative/neutral) on both behavioral data and ERP data was carried out with SPSS and ERP statistical software respectively. The resultant multichannel F-value and t-value time series from ERP analysis were used to generate spatial patterns by interpolation technique, for the control of non-spherical distribution of the error about ERP data, the significant level of F have been reduced to its half of original value.ResultsNo significant difference was found for both reaction time and accuracy. Multi-channel grand-averaged ERPs and spatiotemporal patterns of ERP have been displayed. Three grand waveforms were similar but can still see differences. ERP components included: N150, N200, P250, N400, P500 with scalp distribution: N200,P250 (anterior head); N400, P500 (posterior regions). SPM (F) suggest significant emotional effects occurred mainly in three periods: (1) left occipital (200-220ms); (2) central and left prefrontal (270-300ms); (3) occipital-parietal region (left 560—580ms, right 620—630ms)ConclusionForgas purposed affect infusion model (AIM) that suggested that cognitive tasks can be handled by four processing strategy. When subjects were familiar to the tasks, direct access strategy usually avoid the emotional impact. Our results suggest direct access strategy was used.Although no significant the emotional effect was found, the spatialtemporal patterns ERP showed activation in many brain areas after 200 ms, during the period of 270-300ms, the left prefrontal and central-frontal suggested that the effects may be relevant to the non-emotional information led to the attention bias, it can impact the cognitive processing of task-related stimulation. The relationships among wide brain areas activated need to be further explored, this study suggested ERP as evaluation indicators of emotion was more sensitive than behavior. Both could be separated for exploring emotion. |
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