Dalecki Anna, Johnstone Stuart J, Croft Rodney J
School of Psychology, University of Wollongong, Wollongong, Australia; Illawarra Health and Medical Research Institute, Wollongong, Australia.
School of Psychology, University of Wollongong, Wollongong, Australia.
Int J Psychophysiol. 2015 Jun;96(3):149-54. doi: 10.1016/j.ijpsycho.2015.04.011. Epub 2015 Apr 23.
P50 suppression refers to the amplitude-reduction of the P50 event related potential to the second (S2) relative to the first (S1) of identical auditory stimuli presented 500ms apart. Theory suggests that refractory periods (RPs) and/or inhibitory inputs (II) underlie P50 suppression. The present study manipulated interval between stimulus pairs (IPI: 2, 8s) and direction of participants' attention (Attention, Non-Attention) in order to determine which theory best explains P50 suppression. The rationale is that: 1/ RP and II predict opposite effects of manipulating the functionality of the mechanism responsible for S2P50 suppression (e.g. reducing function would increase S2P50 according to the II and decrease S2P50 according to the RP hypothesis); 2/ IPI2 (relative to IPI8) will reduce functionality of the mechanism responsible for S2P50 suppression, as it results in less recovery of (and a greater challenge to) that mechanism - RP would thus predict reduced S2P50, whereas II would predict enhanced S2P50 amplitude; and 3/ where the mechanism responsible for S2P50 suppression is challenged (i.e. at IPI2, due to insufficient recovery), Attention (relative to Non-Attention) will enhance functionality of this mechanism - RP would thus predict increased S2P50, whereas II would predict reduced S2P50 amplitude. In the Non-Attention paradigm, reducing IPI from 8 to 2s tended to increase S2P50 amplitude (and consequently impaired P50 suppression), and in the 2s IPI paradigm, directing attention towards the stimuli reduced S2P50 amplitude (and improved P50 suppression), with both effects supporting the II hypothesis only.
P50抑制是指在间隔500毫秒呈现的相同听觉刺激中，第二个刺激（S2）相对于第一个刺激（S1）的P50事件相关电位的幅度降低。理论表明，不应期（RP）和/或抑制性输入（II）是P50抑制的基础。本研究操纵了刺激对之间的间隔（刺激间隔时间：2、8秒）以及参与者的注意力方向（注意、非注意），以确定哪种理论最能解释P50抑制。其基本原理是：1/RP和II预测了操纵负责S2P50抑制的机制功能的相反效应（例如，根据II假设，降低该机制功能会增加S2P50，而根据RP假设则会降低S2P50）；2/相对于刺激间隔时间8秒，刺激间隔时间2秒会降低负责S2P50抑制的机制的功能，因为这会导致该机制的恢复减少（并带来更大挑战）——因此，RP预测S2P50会降低，而II预测S2P50幅度会增强；3/当负责S2P50抑制的机制受到挑战时（即刺激间隔时间为2秒时，由于恢复不足），注意（相对于非注意）会增强该机制的功能——因此，RP预测S2P50会增加，而II预测S2P50幅度会降低。在非注意范式中，将刺激间隔时间从8秒减少到2秒往往会增加S2P50幅度（从而损害P50抑制），而在刺激间隔时间为2秒的范式中，将注意力导向刺激会降低S2P50幅度（并改善P50抑制），这两种效应均仅支持II假设。
