Study On Characteristics Of Visual Event-related Potential Evoked By Different Stimulus Fields And Its Application In Forensic Medicine

Objective: By comparing monocular and binocular event-related potential(ERP)evoked by different stimulative field,we aimed to find out the characteristics and differences of waveform and distribution of monocular and binocular ERP,and expecting to provide a basis for objective evaluation of visual field function.Methods: 20 volunteers with normal vision were enrolled in this study.We used the oddball multiple stimulus model,by regarding full field as non-target stimulation(70%),left and right half fields as target stimulation(15% respectively).The ERP responses of the both eyes,left eye and right eye of each subject were recorded and the peak latency and amplitude of P1,N1,P2,N2,P3 components were extracted.The data obtained were statistically analyzed.We used paired t-test for comparing the difference between different eyes,and ANOVA method for analysis of variance between electrodes.Results:(1)The early components:The latency of binocular P1 was significantly shorter than that of the monocular(p <0.05).While the latency of binocular N1 was longer than that of the left eye and the right eye(p <0.05).There was no statistics difference between the two groups in the latency of P2,neither the latency of the left and the right eye nor the amplitude of the three.(2)The late components: under the stimulation of the left and the right half visual field,the amplitude of binocular N2 and P3 were larger than that of the monocular at the central parietal area and the parietal area,while there was no statistics difference in latency between the three.(3)The grand average ERP waveform characteristics: under the stimulation of the left and the right half visual field,P1 appeared during 80-140 ms,mainly at the occipital,and binocular P1 appeared earlier.N1 appeared during 140-220 ms and was widely distributed,and binocular N1 appeared later.P2 appeared during 180-270 ms,mainly at forehead and the parietal area.There is no statistics difference between the eyes.N2 appeared during 250-340 ms,mainly at the parietal part,with a larger binocular amplitude at the central parietal region.P3 appeared during 350-500 ms,mainly at the top,and the binocular amplitude was larger.Conclusion:(1)The P3 component of ERP which evoked by different stimuli field could reflect that the subjects can recognize the target stimulus.Qualitatively and quantitatively,the presence or absence of P3 composition could be used to objectively evaluate whether subjects have visual field defects.(2)There were differences in P1,N1,N2,P2 in monocular and binocular ERP evoked by different stimulation field : under binocular conditions,latency of P1 was shorten,latency of N1 was prolonged,and the amplitude of N2 and P3 increased.In forensic clinical identification,with the above characteristics,we could determine whether the subjects have binocular vision,whether they cooperate with the examination and how well they cooperate,as well as providing electrophysiological evidence for identifying feigned blind.