Many studies observed changes in event-related potential (ERP) during Odd-ball task, but the possible internal relationship among them has not been analyzed through experimental task pattern.OBJECTIVE:
To explore the relationship between changes in ERP and attentional factors through measurement of normal person's ERP in 37 minutes' successive auditory Odd-ball task.DESIGN, TIME AND SETTING:
37 minutes' successive auditory Odd-ball task and blinded evaluation. The experiment was performed at the Department of Rehabilitation Medicine, University of Occupational and Environmental Health between April 2003 and July 2007.PARTICIPANTS:
A total of 20 healthy college students, right handed, were participated in the study. The written informed consent was obtained from all participants.METHODS:
In the task, the students were asked to discriminate rare (10%) target tones (2 kHz) from frequent (90%) non-target tones (1 kHz) and to press button as quickly and accurately as possible after hearing the target tone in continuous 37 minutes (1 214 tone stimulations) which was divided into 4 minutes rehearsal and 3 sessions, 10.9 minutes for each session.MAIN OUTCOME MEASURES:
EEG at forehead zone (Fz), central zone(Cz), and parietal zone (Pz) in response to target tone (target), immediately preceding the target tone (non-target 1) and following the target tone (non-target 2) in each session were averaged separately to analyze changes in ERP components, i.e. N1 and P2 of non-target 1 and non-target 2, N1, N2 and P3 of target in 3 sessions and topographic distribution. Single trial analysis of P3 was also performed. After performing the task, all students answered the questionnaire about the degree of their interest, awareness and attention during three sessions.RESULTS:
①Amplitude of N1 of non-target 1, amplitude of N2 of the target and amplitude of P3 of the target at different sessions changed significantly. ②Amplitude of N1 of non-target 1 was significantly smaller than that of non-target 2 and target in session 2 and session 3 on Fz, Cz and Pz, latency of P2 of non-target 1 was significantly smaller than that of non-target 2 in session 2 on Fz, Cz and Pz, and in session 3 on Fz. Amplitude of P2 of non-target 1 was significantly smaller than that of non-target 2 in session 2 on Cz and in session 3 on Fz, Cz and Pz. The most sensitive position in changes of ERP was on Fz. ③ The waveform of averaged ERP of non-target 1 had positive and negative components of N1 and P2 and returned to the baseline 300 ms after the stimulation and that of non-target 2 returned to the baseline 450 ms after the stimulation on Fz and Cz. ④Single trial analysis of P3 showed that the incidence of type 2 (No P3 component) was significantly larger on Fz than on Pz in all 3 sessions; and incidence of type 2 significantly larger in the session 3 than in session 1 on Fz and Cz. ⑤There was no significant difference in response time in three sessions. ⑥All Subjects answered the questionnaire, and they thought the task was quite easy. They were concentrated on the task at first but soon felt the task was too easy and boring, so they lost their attention sometimes and automatically performed the task, but no one fell in sleep during the test.CONCLUSION:
During 37 minutes' successive auditory Odd-ball task, changes in ERP components result from cognitive adjustment and the relations between them might show the habituation of the subjects, and reflected the effect of different attentional factors.