Time discrimination in the mentally retarded: Latency changes in the evoked potentials with visual masking paradigm

本研究由两部分组成。首先分析了注意力在时间（瞬间）上转移的规律。分析了记忆可及性与目标情境（启动效应）的关系。第一部分：测量视觉erp与选择性注意的关系。连续闪现两个目标对（S1-S2和S3-S4），每个目标对由一个数字(N)和一个短ISI的棋盘(C)组成。NC-NC和CN-CN序列以相同的随机顺序呈现。受试者的任务是为棋盘上的数字命名和匹配模式。在一个会话中目标是数字，而在另一个会话中目标是棋盘。通过对目标刺激和非目标刺激的枕部N1振幅测量两种注意条件对注意转移的时间调节作用。一种注意条件是被试在S1呈现前知道目标位置，另一种注意条件是被试在S1呈现前不知道目标位置。结果表明：(1)正常被试对注意力转移有调节，即关注目标而忽视非目标；(2)智障和精神分裂症被试对非目标和目标都有关注。第二部分：两张熟悉的动物/物体的图片（S1和S2）以短时间间隔呈现。分析了S2命名的反应时间（RT）和对S2的ERP N400。参数为S1与S2在意义上的接近或距离。数据表明：(1)当S1和S2的意义距离较远时，RT的振幅更长，N400的振幅更大；(2)智障者与正常人的趋势相同。

The research was composed of two sections. First analyzed the regulation of attention transfer in time (in a split of a second). Second analyzed the relationship between memory accessibility and target context (the effect of priming).First section: Visual ERPs were measured in relation to selective attention directed to positions in time. Two target pairs (S1-S2 and S3-S4), each composed of a number (N) and a checkerboard (C) with short ISI, were flashed successively. NC-NC and CN-CN sequences were presented with the same probability in random order. A subject's task was naming for the number and pattern-matching for the checkerboard. The target was the number in a session, while the checkerboard in another session. Effects of two attentional conditions on the requlation of attention transfer in time were measured by the amplitude of the occipital N1 to the target and nontarget stimuli. One attentional condition was Focused in which a subject knew the target position prior to S1 presentation and another was Divided in which the subject did not know the target position prior to S1. The data suggested that (1) the normal subject regulated his attention transfer, that is, attending to the target and disregarding the nontarget, (2) mentally retarded and schizophrenia attended to the nontarget as well as to the target.Second section: Two pictures (S1 and S2) of familiar animals/objects were presented with short intervals. Reaction time (RT) for the S2 naming and the ERP N400 to S2 were analyzed. Parameter was closeness or distance in meaning between S1 and S2. The data suggested that (1) RT was longer and N400 was larger in amplitude when S1 and S2 were distant in meaning and (2) the same tendency was found for the retarded people as for the normal subjects.