Decision-related activity in sensory neurons reflects more than a neuron's causal effect.
Decision-related activity in sensory neurons reflects more than a neuron's causal effect.
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DOI：
10.1038/nature07821
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发表时间：
2009-05-07
期刊：
影响因子：
64.8
通讯作者：
Cumming, Bruce G.
中科院分区：
文献类型：
--
作者：
Nienborg, Hendrikje;Cumming, Bruce G.
在感知决策过程中，感觉神经元的活动与受试者的感知相关，即使物理刺激是相同的。这种相关性的起源尚不清楚。目前的理论提出了噪声在感觉神经元中对感知决策的因果效应，但它可能是由与感知选择（自上而下）相关的不同大脑状态引起的。这两种方案对感觉神经元在形成决策中所扮演的角色有着非常不同的含义。在这里，我们使用白噪声分析来测量与选择相关的V2神经元的调节功能，同时测量刺激的变化如何影响受试者（两只猕猴）的感知决策。在因果模型中，刺激对决策的更强影响，由感觉神经元介导，与更强的选择相关活动相关。然而，我们发现，随着试验的进行，这些测量结果会朝不同的方向变化——这与因果模型不一致。对奖励大小效应的分析也支持同样的结论。最后，选择与神经元增益的变化有关，这与因果模型不相容。如果选择与由自上而下的现象引起的神经元增益变化有关，这三个结果都很容易解释，这种现象与注意力非常相似。我们得出结论，自上而下的过程有助于选择相关的活动。因此，即使形成简单的感觉决定，也涉及认知过程和感觉神经元之间复杂的相互作用。
During perceptual decisions, the activity of sensory neurons correlates with a subject’s percept, even when the physical stimulus is identical. The origin of this correlation is unknown. Current theory proposes a causal effect of noise in sensory neurons on perceptual decisions, but it could result from different brain-states associated with the perceptual choice (top-down). These two schemes have very different implications for the role played by sensory neurons in forming decisions. Here, we used white-noise analysis to measure tuning-functions of V2 neurons associated with choice and simultaneously measure how the variation in the stimulus affects subjects’ (two macaques) perceptual decisions. In causal models stronger effects of the stimulus upon decisions, mediated by sensory neurons, are associated with stronger choice-related activity. However, we find that over the timecourse of the trial, these measures change in different directions—at odds with causal models. An analysis of effect of reward size supports the same conclusion. Finally, choice was associated with changes in neuronal gain that are incompatible with causal models. All three results are readily explained if choice is associated with changes in neuronal gain caused by top-down phenomena that closely resemble attention. We conclude that top-down processes contribute to choice-related activity. Thus even forming simple sensory decisions involves complex interactions between cognitive processes and sensory neurons.
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