ERP And SSVEP Study Of Stroopeffect

The Stroop effect is a well-known cognitive phenomenon with wide applications inexperimental psychology and clinical practices，which reflects the selective attentionand conflict interference of the brainactivity.EEG data with high time resolution is verygood for investigate the time course of Stroop effect.Previous study has found thesignificantmarker on ERP component of the Stroop effect.While the results can only begotten from multisubjects, which will block the application of Stroop effect.This studyprocesses the data with some methods of spatial filter and found that the method ofGroupsim can extract the ERP component with Stroop effect difference from singlesubject. This study first introduces the SSVEP frequency into the Strooptask.It canobtain the ERP signal and SSVEP signal simultaneously and analyse the two signalsindependently, which also provide a new method for other cognitive experiments.15subjects EEG data were recorded with the Chinese character word ink colorStroop task, and the ERP waveform was averaged. From the ERP waveform, it wasfound that the N2b and N450components had the significantdifference between eachcondition. With the method of Groupsim which is based on the principle of maximizingthe difference between conditions, the difference between conditions from singlesubject’s EEG datawas detected.Single subject analysis facilitates the use of Strooptaskin clinical applications.It was firstly introduced SSVEP frequency to Strooptask.EEG data of five subjectsfrom the Stroop task were studied, which is target marked and background markedrespectively.The envelope of SSVEP signal extracted by the CCA method showeddifference between conditions.It was also found the SSVEP mark influence of ERP, thatis background marked ERP has longer latency of P1and/or N2than target marked ERP.It was proposed the phase modulation SSVEP background Stroop task, which can getthe ERP signal and SSVEP signal simultaneously without mutal interference.The ERPsignal shew difference between conditions in the time window between400ms and600ms.The envelope of SSVEP signal shew the decline related with cognitive activity.From the ERP signal we also found the poststimulus changes of alpha total activity arerelated with its prestimulus level.The new method of phase modulation SSVEP mark also provides a novel and useful tool for ERP and SSVEP analysis in a wide range ofcognitive experiments, which can detect both the transient response and the steady stateresponse of the brain.