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Objective:To explore the spatio-temporal dynamics of brain mechanisms in visual change detection by 256-channel event-related potential (ERP) and low-resolution electromagnetic tomography (LORETA) analyses.Methods：ERP were recorded in 12 healthy participants during performing an S1-S2 matching task.Visual stimuli defined by color and shape.Each trial consisted of two sequentially presented stimuli (S1 and S2),where S2 was either the same as S1,different from S1 in shape only,different in color only,or different in both color and shape.Subjects matched the stimuli according to task demands：attending to color and attending to shape.Result：Change condition elicited change-related positivity (CRP) ranging 135～165 ms.The estimated source regions contributing to CRP were lingual gyrus and cuneus of occipital lobe.N200 was elicited in no change and task-irrelevant change condition ranging 235～275 ms.The source for N200 was in the right temporal fusiform gyrus,middle temporal gyrus and parahippocampal gyrus.In the time window of 240～320 ms,N270 was elicited in all change conditions.The N270 source was localizable to the anterior cingulated cortex and amygdala.Conclusion：In the early stage,CRP reflects the preattentive processing of visual changes.The LORETA result confirms that CRP is generated in the early visual areas.N200 may be related to the active ignored processing of task-irrelevant change.The source for N200 is in the right temporal fusiform gyrus,middle temporal gyrus and parahippocampal gyrus.In the late stage,N270 reflects the advanced processing of visual change in the human brain.The N270 source may be in anterior cingulate cortex (ACC) and amygdala.
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@# Objective To investigate the cortical activities for processing exogenous stimulus-related information conflict and endogenous mental-related information conflict.Methods Event-related potentials (ERPs) were recorded while 15 healthy subjects performed a digit matching task. Each trial consisted of two sequentially presented digits (S1～S2), where S2 was either the same as S1 (S-) or different from S1 (S+) in digital value. Subjects pressed a button of a push-pad when S2 was the same as S1 and pressed the other button when S2 was different from S1 in the first session. Furtherly, they were required to calculate the difference between S1 and S2, and compare their calculation result with digit '3' in the second session. They pressed a button when the calculation result was equal to '3' (M-) and pressed the other button when it was not (M+). Three trial types were included: same numbers but their difference was not equal to '3' (S-M+), different numbers but their difference was '3' (S+M-) and different numbers but their difference was not '3' (S+M+). Results Following S2 onset, a component N270 was broadly elicited at all the scalps by S+, S+M- and S-M+. N270 and N400 were elicited in series by S+M+. The maximal amplitude of N270 was at the posterior scalp while the maximal amplitude of the N400 was at the central areas. Conclusion The different spatio-temporal distributions of the two negative potentials suggested that exogenous and endogenous information conflicts were serially processed in the human brain by the conflict processing system of multiple neural substrates.
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@#ObjectiveTo investigate the characteristics of event-related potential (ERP) N270 and the value of ERP N270 to detect the cognitive function in patients with epilepsy.MethodsThirty-five epileptics were divided into carbamazepine (CBZ) group (n=10), valproate (VPA) group (n=10) and no treatment group (n=15) according to drugs they took, and other 10 healthy subjects were selected as the control group. All subjects were evaluated by Mini-Mental State Examination (MMSE), and ERP was recorded at same time.ResultsAll patients in three groups showed a delayed and smaller N270 than the control group ( P<0.01). VPA group had the lowest N270 amplitude. The amplitude of P300 elicited in the match condition decreased in the VPA group compared with other three groups ( P<0.05), but latency of the VPA group was not different from other three groups.ConclusionCognitive impairment is present in epilepsy patients, and the effect of anti-epileptic drug VPA on ability of patients to process conflict is more evidence than CBZ. The sensitivity of N270 to detect early cognitive impairment in epileptics is higher than P300.
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@#ObjectiveTo find the cognitive function impairment in children with benign epilepsy with centro-temporal spikes and to find a sensitive index which can reveal the cognitive function impairment.Methods21 patients with benign epilepsy with centro-temporal spikes participated in this study. 21 normal subjects, matched for age, gender, years of education and family socioeconomic status, served as controls. Subjects were asked to judged weather the two sequentially presented numbers (S1 and S2) in a digit pair were identical or not, while event-related potential (ERPs) were recorded from electrodes on their scalp.ResultsN270 was evoked by S2 of the conflict condition in either controls or patients. Compared with control group, N270 latency was significantly prolonged and the amplitude decreased in the patient group. However, the peak latency and amplitude of P300 were not changed significantly in patient group. ConclusionChildren with benign epilepsy with centro-temporal spikes as a group show cognitive function impairment. Conflict negative N270 can be employed as a method for evaluating cognitive disturbance, which seems subtler than P300 in detecting mild cognitive function impairment.
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Objective To find a sensitive index and to investigate the working memory impairment of patients with amnestic mild cognitive impairment.Methods Fifteen patients with amnestic mild cognitive impairment,15 healthy matching aging controls were performed a matching-to-sample task while event-related potential(ERP),reaction time and correct rate were recorded.Subjects were required to press a button in the match condition and another button in the conflict condition.Results In the matching condition,there was no difference between the two groups in distribution(parietal lobe),peak latency and amplitude of P300(F_ 1,28 =1.0324,P=0.3183;F_ 2,42 =0.543,P=0.585).In the conflict condition,the distribution of N270 was fore head,and its latency of patient group were more delayed than the aging group(F_ 1,28 =25.3264,P=0.000),but its amplitude showed no significant changes(F_ 1,28 =0.507,P=0.482).The result of brain mapping showed same change.Conclusion The N270 component is more sensitive than P300 to reflect the central executive function impairment of working memory in patients with amnestic mild cognitive impairment.