Objective: To analyze the changes of normal adults' forty Hertz brain electrical signal under different degrees of cognitive load letters short-term memory so as to preliminarily understand the effects of cognitive load on brains' forty hertz brain electrical signal;to preliminarily discuss the quantification of letters short-term memory stimulus and its degree of load about the forty event-related brain potentials research;to preliminarily evaluate the practicability of nonlinear dynamic parameters under this stimulus.Methods: Fifty normal adults were given different degrees of cognitive load letters short-term memory.Then EEG signals was collected and analyzed by using nonlinear dynamic parameters commonly used indicators.Results:Under different degrees of cognitive load letters short-term memory,normal adult brains' nonlinear dynamic parameters on every lead has obvious and statistically significant changes(P<0.05); normal adult brains' nonlinear dynamic parameters in the cognitive activity is greater than theirs in the quiet condition.there hasn't been obvious presence of high frequency signals under the quiet state of opening and closing our eyes.we can't obtain the nonlinear dynamic parameters by data processing.Conclusion: Repeated recognition of letter short-term memory can be used as appropriate exciting event to induce brain's high frequency signals.Nonlinear dynamic parameters,such as correlation dimension,complexity and approximate entropy,can be used as the measurements of brain's advanced-neural cognitive activity.%目的:比较分析不同程度认知负荷字母短时记忆下正常成年人40hz脑电信号的变化,以初步了解认知负荷对大脑40hzERP信号的影响,初步探讨字母短时记忆刺激事件及其负荷程度对40hzERP研究的量化性,初步评价在该刺激事件下非线性动力学参数的实用性.方法:选取正常成年人50例,给予不同认知负荷字母短时记忆刺激,采集脑电信号并用非线性动力学参数常用指标进行数据处理分析.结果:①正常成年人在不同认知负荷字母短时记忆刺激下,大脑各导联非线性动力学参数均有显著变化,并具有统计学意义(P<0.05);②正常成年人在认知活动中的非线性动力学参数值高于安静状态下,在安静睁眼和闭眼状态下无明显高频信号的出现,数据处理未求得非线性动力学参数.结论:① 字母短时记忆重复再认可以作为诱导大脑高频信号的适宜刺激事件;②非线性动力学参数关联维数、复杂度及近似熵可以作为大脑高级神经认知活动的检测指标.
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