Kekoni J, Hämäläinen H, McCloud V, Reinikainen K, Näätänen R
Department of Psychology, University of Helsinki, Finland.
Electroencephalogr Clin Neurophysiol. 1996 Mar;100(2):115-25. doi: 10.1016/0013-4694(95)00231-6.
Effects of attention to, and probability of sudden changes in, repetitive stimuli on somatosensory evoked potentials (SEP) were studied. Low - (30 Hz) and high-frequency (140 Hz) vibratory stimuli were delivered in random order to the middle finger of the left hand with different presentation probabilities in different blocks. Also ignore conditions were administered. In the ignore conditions, the probability had no effect on SEPs. However, when the standard stimuli were omitted, the "deviants" elicited small N140 and P300 deflections not observed in response to deviants when standards were also present. In the attention conditions, deviant stimuli (targets) elicited large N250 and P300 deflections which increased in amplitude with a decreased target probability. However, when subjects counted infrequently presented "deviants" alone (standards omitted) the enhanced N140 and the P300 with shortened latency were elicited, but no N250 wave could be found. At the ipsilateral side, a distinct N200 deflection was seen which could be the N250 with a shorter latency because of an easier task (detection instead of discrimination). The results might be interpreted as suggesting that the somatosensory N250 is related to conscious detection of target stimuli.
研究了对重复刺激的关注以及突然变化的概率对体感诱发电位（SEP）的影响。低频率（30Hz）和高频率（140Hz）的振动刺激以随机顺序施加于左手的中指，在不同的组块中具有不同的呈现概率。同时也设置了忽略条件。在忽略条件下，概率对SEP没有影响。然而，当标准刺激被省略时，“偏差刺激”引发了小的N140和P300偏转，而当标准刺激也存在时，对偏差刺激的反应中未观察到这种偏转。在关注条件下，偏差刺激（目标）引发了大的N250和P300偏转，其幅度随着目标概率的降低而增加。然而，当受试者单独计数不常出现的“偏差刺激”（省略标准刺激）时，引发了增强的N140和潜伏期缩短的P300，但未发现N250波。在同侧，观察到一个明显的N200偏转，由于任务更容易（检测而非辨别），它可能是潜伏期更短的N250。结果可能被解释为表明体感N250与目标刺激的意识检测有关。
