Department of Psychology, University of Connecticut, Storrs, Connecticut 06269, and Department of Biological Sciences, State University of New York College of Optometry, New York, New York 10036.
J Neurosci. 2014 Mar 12;34(11):3888-900. doi: 10.1523/JNEUROSCI.4969-13.2014.
Awake mammals can switch between alert and nonalert brain states hundreds of times per day. Here, we study the effects of alertness on two cell classes in layer 4 of primary visual cortex of awake rabbits: presumptive excitatory "simple" cells and presumptive fast-spike inhibitory neurons (suspected inhibitory interneurons). We show that in both cell classes, alertness increases the strength and greatly enhances the reliability of visual responses. In simple cells, alertness also increases the temporal frequency bandwidth, but preserves contrast sensitivity, orientation tuning, and selectivity for direction and spatial frequency. Finally, alertness selectively suppresses the simple cell responses to high-contrast stimuli and stimuli moving orthogonal to the preferred direction, effectively enhancing mid-contrast borders. Using a population coding model, we show that these effects of alertness in simple cells--enhanced reliability, higher gain, and increased suppression in orthogonal orientation-could play a major role at increasing the speed of cortical feature detection.
清醒的哺乳动物每天可以在警觉和非警觉的脑状态之间切换数百次。在这里，我们研究了警觉状态对清醒兔子初级视觉皮层 4 层中两类细胞的影响：假定的兴奋性“简单”细胞和假定的快速尖峰抑制神经元（疑似抑制性中间神经元）。我们表明，在这两类细胞中，警觉状态均增强了视觉反应的强度和可靠性。在简单细胞中，警觉状态还增加了时间频率带宽，但保持了对比度敏感性、方向调谐以及对方向和空间频率的选择性。最后，警觉状态选择性地抑制了简单细胞对高对比度刺激和与首选方向正交运动的刺激的反应，有效地增强了中对比度边界。使用群体编码模型，我们表明，这些简单细胞中的警觉状态的影响——增强的可靠性、更高的增益和增加的正交方向抑制——可以在提高皮层特征检测速度方面发挥重要作用。
