Boston University.
Massachusetts Institute of Technology.
J Cogn Neurosci. 2018 Jul;30(7):935-950. doi: 10.1162/jocn_a_01273. Epub 2018 Apr 26.
Cognitive theories suggest that working memory maintains not only the identity of recently presented stimuli but also a sense of the elapsed time since the stimuli were presented. Previous studies of the neural underpinnings of working memory have focused on sustained firing, which can account for maintenance of the stimulus identity, but not for representation of the elapsed time. We analyzed single-unit recordings from the lateral prefrontal cortex of macaque monkeys during performance of a delayed match-to-category task. Each sample stimulus triggered a consistent sequence of neurons, with each neuron in the sequence firing during a circumscribed period. These sequences of neurons encoded both stimulus identity and elapsed time. The encoding of elapsed time became less precise as the sample stimulus receded into the past. These findings suggest that working memory includes a compressed timeline of what happened when, consistent with long-standing cognitive theories of human memory.
认知理论表明，工作记忆不仅可以保持最近呈现的刺激的身份，还可以保持刺激呈现以来的流逝时间的感觉。以前对工作记忆的神经基础的研究主要集中在持续放电上，持续放电可以解释刺激身份的维持，但不能解释流逝时间的表示。我们分析了猕猴外侧前额叶皮层在延迟匹配类别任务中的单个神经元记录。每个样本刺激都会触发一个一致的神经元序列，序列中的每个神经元都会在一个限定的时间段内发射。这些神经元序列既编码了刺激的身份，也编码了流逝的时间。随着样本刺激逐渐回到过去，流逝时间的编码变得不那么精确。这些发现表明，工作记忆包括一个压缩的时间线，记录了过去发生的事情，这与人类记忆的长期认知理论一致。
