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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Trial-to-trial variability of the prefrontal neurons reveals the nature of their engagement in a motion discrimination task
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Trial-to-trial variability of the prefrontal neurons reveals the nature of their engagement in a motion discrimination task

机译：前额神经元的试验间差异揭示了他们参与运动识别任务的本质

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摘要

During motion discrimination tasks, many prefrontal cortex (PFC) neurons are strongly modulated by the behavioral context, suggesting their involvement in sensory discriminations. Recent studies suggest that trial-to-trial variability of spiking activity characteristic of cortical neurons could be a source of information about the state of neurons and their participation in behavioral tasks. We tested this hypothesis by examining the variability of putative pyramidal PFC neurons, a likely source of top-down influences. The variability of these neurons was calculated as a ratio of spike count variance to its mean (fano factor, FF), while monkeys compared the directions of two moving stimuli, sample and test, separated by a delay. We found that the FF tracked consecutive components of the task, dropping rapidly with the onset of stimuli being discriminated and declining more slowly before each salient event of the trial: The sample, the test, and the response. These time-dependent signals were less consistent in direction selective neurons and were largely absent during passive fixation. Furthermore, neurons with test responses that reflected the remembered sample decreased their FF well before the test, revealing the predictive nature of response variability, an effect present only during the active task. The FF was also sensitive to behavioral performance, exhibiting different temporal dynamics on error trials. These changes did not depend on firing rates and were often the only metric correlated with task demands. Our results demonstrate that trial-to-trial variability provides a sensitive measure of the engagement of putative pyramidal PFC neurons in circuits subserving discrimination tasks.
机译：在运动识别任务中，许多前额叶皮层（PFC）神经元受到行为背景的强烈调节，表明它们参与了感觉识别。最近的研究表明，皮质神经元的尖峰活动特征的试验间变化可能是有关神经元状态及其参与行为任务的信息来源。我们通过检查推定的金字塔形PFC神经元（可能是自上而下的影响的来源）的变异性来检验该假设。将这些神经元的变异性计算为峰值计数变异与其平均值（fano因子，FF）的比率，而猴子则比较了两个运动刺激的方向（样本和测试），但有一个延迟。我们发现FF跟踪任务的连续组成部分，在试验的每个显着事件之前（样本，测试和响应），歧视的发作迅速下降，下降速度更慢。这些时间依赖性信号在方向选择性神经元中不那么一致，并且在被动固定过程中基本上不存在。此外，具有反映出记忆样本的测试反应的神经元在测试前很早就降低了FF，从而揭示了反应变异性的预测性质，这种效应仅在活动任务期间才会出现。 FF对行为表现也很敏感，在错误试验中表现出不同的时间动态。这些变化不取决于解雇率，通常是与任务需求相关的唯一指标。我们的研究结果表明，试验间的差异为假定的金字塔形PFC神经元参与识别任务的电路提供了灵敏的测量方法。

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