The Processing Mechanism Of Different Visual Field Conflict Information And The Clinical Application Of N270

Experiment 1: The impact of different hands' response on the conflict monitoring event-related potential N270Object: To explore the influence of different hands' response on event-related potential N270. Method: Subjects were asked to discriminate whether the two sequentially presented visual stimuli were of the same color while event-related potentials were recorded from their scalps. In the first half of the test, subjects used two different fingers of one hand to press the buttons of a pushpad, while they used the other hand in the other half. Results: N270 component was recorded only in the conflict condition mainly on the centra-frontal area. The mean amplitude of Contingent negative variation (CNV) was significantly higher to the right hand response, and the lasting effect of it did not affect the amplitudes of N160, N200 and N270. The mean amplitudes of N160 and N200 were significantly higher in the left hand response. However, the mean amplitudes of N270 showed no significant difference between left and right hand responses. Conclusion: Different hands' response didn't affect the event-related potential N270.Experiment 2: The processing mechanism of conflict information between bilateral cerebral hemispheresObject: To explore the mechanism of conflict information processing between bilateral cerebral hemispheres. Method: Participants were instructed to use different fingers of one hand to discriminate whether the color of the first stimulus (S1) was the same as that of the second one (S2) in a pair. Stimuli were defined by twofeatures: color and location. According to their color, stimuli were divided into color match (same) and color conflict (different). The stimuli were presented in the left or right visual hemifields. According to their location relation, they were divided into: (1) unilateral visual field, in which S1 and S2 all located in the same visual hemifield; (2) bilateral visual field, in which S1 and S2 located in different visual hemifields. Results: An endogenous event-related potential (ERP) component N270 was elicited in color conflict unilateral condition. It was also elicited in bilateral conditions either color match or color conflict, mainly at fronto-central areas. The mean amplitude of N270 of the hemisphere into which S1 was transmitted was more negative (P< 0.05). Conclusion: Conflict information processing requires the cooperative activities of bilateral cerebral hemispheres, while the S1-transmitting-into-hemisphere is the dominant cerebral hemisphere for conflict processing. Experiment 3: Event related potential N270 can be a sensitive index for diagnosing mild cognitive impairmentObjective: To find the role of conflict negative N270 in the diagnosing of mild cognitive impairment (MCI).Method: Thirteen MCI patients and twenty-eight aged-matched normal controls performed a matching-to-sample task while event-related potential (ERP) was recorded from their scalp. There were two kinds of stimulus pairs in this study: ⑴match condition: the second stimulus (S2) in a pair was identical to the first one (S1); ⑵conflict condition: S2 conflicted with S1 in their color attribute. Subjects were required to press a button in the match condition and another button in the conflict condition.Results: The N270 component was evoked by S2 of conflict condition in both controls and patients. The patient group showed a delayed N270 than the control group. The peak latency and amplitude of P300 differ significantly between the two subject groups.Conclusion: Conflict negative N270 is a new cognitive component and it can be a method for evaluating cognitive impairment of patients. N270 is subtler than P300 to detecting mild cognitive impairment.