Twomey Deirdre M, Murphy Peter R, Kelly Simon P, O'Connell Redmond G
Trinity College Institute of Neuroscience, Lloyd Building, Trinity College Dublin, Dublin 2, Ireland.
Department of Psychology and Leiden Institute for Brain and Cognition, Leiden University, Leiden, The Netherlands.
Eur J Neurosci. 2015 Jul;42(1):1636-43. doi: 10.1111/ejn.12936. Epub 2015 May 28.
The P300 component of the human event-related potential has been the subject of intensive experimental investigation across a five-decade period, owing to its apparent relevance to a wide range of cognitive functions and its sensitivity to numerous brain disorders, yet its exact contribution to cognition remains unresolved. Here, we carry out key analyses of the P300 elicited by transient auditory and visual targets to examine its potential role as a 'decision variable' signal that accumulates evidence to a decision bound. Consistent with the latter, we find that the P300 reaches a stereotyped amplitude immediately prior to response execution and that its rate of rise scales with target detection difficulty and accounts for trial-to-trial variance in RT. Computational simulations of an accumulation-to-bound decision process faithfully captured P300 dynamics when its parameters were set by model fits to the RT distributions. Thus, where the dominant explanatory accounts have conceived of the P300 as a unitary neural event, our data reveal it to be a dynamically evolving neural signature of decision formation. These findings place the P300 at the heart of a mechanistically principled framework for understanding decision-making in both the typical and atypical human brain.
在过去的五十年里，人类事件相关电位的P300成分一直是密集实验研究的对象，这是因为它显然与广泛的认知功能相关，并且对多种脑部疾病敏感，但其对认知的确切贡献仍未得到解决。在这里，我们对由短暂听觉和视觉目标诱发的P300进行了关键分析，以检验其作为“决策变量”信号的潜在作用，该信号会将证据积累到决策界限。与后者一致，我们发现P300在反应执行前立即达到一个固定的幅度，并且其上升速率与目标检测难度成比例，并解释了反应时间的逐次试验差异。当通过对反应时间分布的模型拟合来设置其参数时，对积累到界限的决策过程的计算模拟忠实地捕捉到了P300的动态。因此，在主要的解释性观点将P300视为一个单一的神经事件的情况下，我们的数据表明它是决策形成过程中动态演变的神经特征。这些发现使P300处于理解典型和非典型人类大脑决策的一个有机械原理的框架的核心位置。
