Macquarie University, Australia.
ARC Centre of Excellence in Cognition and Its Disorders, Australia.
J Cogn Neurosci. 2017 Dec;29(12):1995-2010. doi: 10.1162/jocn_a_01177. Epub 2017 Aug 18.
Animacy is a robust organizing principle among object category representations in the human brain. Using multivariate pattern analysis methods, it has been shown that distance to the decision boundary of a classifier trained to discriminate neural activation patterns for animate and inanimate objects correlates with observer RTs for the same animacy categorization task [Ritchie, J. B., Tovar, D. A., & Carlson, T. A. Emerging object representations in the visual system predict reaction times for categorization. PLoS Computational Biology, 11, e1004316, 2015; Carlson, T. A., Ritchie, J. B., Kriegeskorte, N., Durvasula, S., & Ma, J. Reaction time for object categorization is predicted by representational distance. Journal of Cognitive Neuroscience, 26, 132-142, 2014]. Using MEG decoding, we tested if the same relationship holds when a stimulus manipulation (degradation) increases task difficulty, which we predicted would systematically decrease the distance of activation patterns from the decision boundary and increase RTs. In addition, we tested whether distance to the classifier boundary correlates with drift rates in the linear ballistic accumulator [Brown, S. D., & Heathcote, A. The simplest complete model of choice response time: Linear ballistic accumulation. Cognitive Psychology, 57, 153-178, 2008]. We found that distance to the classifier boundary correlated with RT, accuracy, and drift rates in an animacy categorization task. Split by animacy, the correlations between brain and behavior were sustained longer over the time course for animate than for inanimate stimuli. Interestingly, when examining the distance to the classifier boundary during the peak correlation between brain and behavior, we found that only degraded versions of animate, but not inanimate, objects had systematically shifted toward the classifier decision boundary as predicted. Our results support an asymmetry in the representation of animate and inanimate object categories in the human brain.
生物性是人类大脑中物体类别表示的一个强大组织原则。使用多元模式分析方法，已经表明，距离用于区分有生命和无生命物体的神经激活模式的分类器的决策边界的距离与观察者对相同生物性分类任务的反应时间相关[Ritchie，JB，Tovar，DA，& Carlson，TA。视觉系统中新兴的物体表示预测分类的反应时间。 PLoS Computational Biology，11，e1004316，2015；Carlson，TA，Ritchie，JB，Kriegeskorte，N.，Durvasula，S.，& Ma，J.物体分类的反应时间由代表性距离预测。认知神经科学杂志，26，132-142，2014]。使用 MEG 解码，我们测试了当刺激操作（降级）增加任务难度时，是否存在相同的关系，我们预测这将系统地减小激活模式与决策边界的距离，并增加反应时间。此外，我们还测试了距离分类器边界是否与线性弹道积累器中的漂移率相关[Brown，SD，& Heathcote，A.最简单的选择反应时间完整模型：线性弹道积累。认知心理学，57，153-178，2008]。我们发现，距离分类器边界与反应时间、准确性和在生物性分类任务中的漂移率相关。按生物性划分，在生物性刺激比无生命刺激的时间过程中，大脑和行为之间的相关性持续时间更长。有趣的是，当检查大脑和行为之间的峰值相关性期间的分类器边界距离时，我们发现只有降级的有生命的物体，而不是无生命的物体，正如预测的那样，系统地向分类器决策边界移动。我们的结果支持人类大脑中生物性和无生命物体类别的表示存在不对称性。
