事件相关电位客观评估视敏度的法医学应用

目的研究不同视敏度水平的事件相关电位(event-related potential,ERP)成分特征,以期为视敏度的客观评定提供理论依据。方法选取16名被试进行单眼刺激。要求被试眼平视前方屏幕,注意屏幕中央的视觉刺激并对朝向不同的刺激进行计数。屏幕的中央会显示3种不同视敏度水平所对应的视标刺激图片,分别记录其ERP结果。结果 (1)阈上视敏度水平一致刺激的P_1振幅高于阈值、阈下视敏度水平一致刺激的P_1振幅,阈值和阈下视敏度水平一致刺激的P_1振幅差异无统计学意义,冲突刺激与一致刺激在3种视敏度水平的趋势类似。(2)阈上和阈值视敏度水平都出现了潜伏期在340~500 ms内的P300成分;阈下视敏度水平在相应的时间窗内无P300成分。3种视敏度水平的P_(300)振幅差异有统计学意义,振幅由大到小分别为阈上、阈值、阈下视敏度水平。结论 ERP技术可以成为法医学客观评定视敏度的新手段。

Forensic Application of Objective Assessment on Visual Acuity by ERP

Objective T o explore the com position characteristic of event related potential (E R P ) in dif-ferent visual acuity levels, and to provide theoretical basis for the objective assessm ent of visual acuity. Methods M onocular stim ulus w as perform ed on 16 selected subjects. T he subjects w ere required to look straight at the screen ahead and count the am ount of stim uli from different directions. T he pictures of optotype stim ulus w hich corresponding to three different visual acuity levels w ere show ed in the center of the screen. The ERP results w ere recorded separately. Results (1) The P1 am plitudes of m atch stim uli recorded under the supra-threshold visual acuity level w ere higher than that of m atch stim uli recorded under the threshold and sub-threshold visual acuity levels. T here w as no significant difference betw een the P 1 am plitudes of m atch stim uli recorded under the threshold and sub-threshold visual acuity levels. T he tendency of conflict stim uli w as sim ilar to that of m atch stim uli under three visual acuity levels. (2) In the 340-500 m s post-stim ulus range, P 300 com ponent w as found under supra-threshold and threshold visual acuity levels; no P 300 com ponent w as found in corresponding tim e w indow under sub-threshold visual acuity. T he differences of P 300 am plitudes am ong three visual acuity levels w ere statistically significant. T he am plitudes from high to low w ere the supra-threshold, threshold and sub-threshold visual acuity levels. Conclusion E R P can be a potential new m ethod for the objective assessm ent of visual acuity in forensic m edicine.