Winter Rebecca, Harrar Vanessa, Gozdzik Marta, Harris Laurence R
Centre for Vision Research, York University, Toronto, Ontario, Canada.
Brain Res. 2008 Nov 25;1242:54-8. doi: 10.1016/j.brainres.2008.06.090. Epub 2008 Jul 2.
Tactile stimulation usually occurs as a combination of an active movement (reaching out to touch a surface) and a sensation (actually feeling the surface against the skin). The brain has information about the active component (the motor command) before it occurs because of efference copy, while the passive component must be transduced before it can be processed. Since the active and passive tactile components are available to the brain at different times, determining the time of touch requires calculation worked backwards from the passive sensation, and/or worked forward from the active motor command. In order to determine which touch process is perceived more quickly, we varied the relative delay between an active and a passive touch signal and determined the relative time perceived as simultaneous. A passive touch needed to be presented before an active key was pressed in order for the two touches to be perceived as simultaneous, but this timing difference was not significant. In order to test the plasticity of the active and passive touch systems, we exploited the fact that the point of subjective simultaneity between two stimuli can sometimes be altered by repeated exposure to asynchronous presentation. We exposed subjects to an active key press/ passive touch pair delayed by 250 ms. This exposure increased the range of relative delays between active and passive touches at which the pairs were judged as simultaneous. This is consistent with an adaptive change in the processing of active touch.
触觉刺激通常表现为主动动作（伸手触摸一个表面）和感觉（实际感受表面与皮肤的接触）的结合。由于存在传出副本，大脑在主动动作（运动指令）发生之前就已经有了关于它的信息，而被动成分在被处理之前必须先被转换。由于主动和被动触觉成分在不同时间被大脑接收，确定触摸时间需要从被动感觉反向计算，和/或从主动运动指令正向计算。为了确定哪种触摸过程被更快地感知，我们改变了主动和被动触摸信号之间的相对延迟，并确定了被感知为同时发生的相对时间。为了使两次触摸被感知为同时发生，被动触摸需要在按下主动按键之前呈现，但这种时间差异并不显著。为了测试主动和被动触摸系统的可塑性，我们利用了这样一个事实，即两个刺激之间的主观同时性点有时可以通过反复接触异步呈现而改变。我们让受试者接触延迟250毫秒的主动按键/被动触摸对。这种接触增加了主动和被动触摸之间相对延迟的范围，在这个范围内，这对刺激被判断为同时发生。这与主动触摸处理过程中的适应性变化是一致的。
