ERP Study Of Attention And Emotion In The Mental Fatigue

There are different types of mental fatigue in different occupations, and the mental fatigue has tough impact on the individual activity physiologically and psychologically. There are many relative studies in military or other special fields that show that the level of arouse and cognition are reduced by fatigue, especially for the attention, in accompany with the shift of emotion and affection. There is much limitation in the past studies in which subjective evaluation was involved. ERP was employed in the present study in which the classical and creative modes were used to explore the processing characteristic of attention after fatigue, and the influence of fatigue upon emotion was also discussed in the study.32 male volunteers attended in the experiment, and the subjects were divided into two groups (driving group and VDT group) according to the different cognitive load. The experiment was employed before and after fatigue so as to get the grades of different scales and experiment data. The objective index and subjective evaluation were both used to assess the characteristic of cognition and emotion before and after fatigue. The experiment consisted of three parts: first, the Fatigue scale-14, POMS, and VAS were employed to evaluate the subjects'state of fatigue and emotion. Secondly, different ERP modes (classical MMN, optimal MMN, Novelty Oddball, CNV) were used to assess the features of attention in the mental fatigue. We discussed the amplitudes and latencies of classical MMN, optimal MMN, P3a, P3b, and CNV to probe into the ability of shift from unconsciousness to consciousness. Last, the modes of GO-NOGO and Face recognition were used to evaluate the changes of emotion in the fatigue by the analysis of N170, NOGO-N2, and NOGO-P3.The main conclusions of the present study are as follows:1. The automatic processing of information was influenced by the mental fatigue, and the pre-attention was impaired; in addition, the advantages of right hemisphere at front cortex disappeared after fatigue, which might be due to the reduction of performance in right hemisphere at front cortex. The reduction of the amplitudes of both classical and optimal MMN after fatigue occurred in both driving group and VDT group. The amplitudes of optimal MMN showed that the two groups had the advantages of right hemisphere over the left hemisphere; however, such difference disappeared after fatigue.2. The function of performance was damaged after fatigue, and the ability of involuntary attention and selective attention was impaired. The impairment of orient response indicated that the awareness and judgment of the signal of danger were damaged after fatigue, and the self-protection was also absent. Further, the reduction of selective attention demonstrated that the ability to respond to relative mission was declined after fatigue. The conclusion could be proved by the reduction of amplitudes of P3a and P3b in both groups after fatigue. The peak of P3a was located at frontal cortex, and the obvious advantages of the frontal cortex could be seen before fatigue, however, such advantages disappeared after fatigue. The decline of amplitudes of P3a showed the impaired function of performance after fatigue.3. Maintenance of attention was damaged after mental fatigue, and the expectation and cognitive motion were also reduced, which could be supported by the reduction of average amplitudes of CNV and CNV late component after fatigue, compared to the amplitudes before fatigue.4. Attentional preference to the negative emotion vanished after mental fatigue, and the response to the outside threat for self-protection was attenuated, which could be corroborated by the higher amplitude of N170 to angry faces than that of N170 to happy faces before fatigue, however, there was no significant difference between them after fatigue.5. The ability to supervise the conflict information and restrain the response was attenuated. The ability to restrain the information of negative emotion was declined by the fatigue, which demonstrated that fatigue gave rise to much more negative emotion. The conclusion could be proved by the decline of amplitude of NOGO-N2 and increased amplitudes of NOGO-N2 to the angry faces.6. The subjective evaluation showed the obvious sense of fatigue after mission, and each scale grade was significantly increased after fatigue, which indicated that the negative emotion was stimulated by fatigue. Scores of A, F, T in POMS were increased and the indexes of Alert, Anxious and Irritable were all different from those before fatigue.