Department of Neurobiology, Stanford University, Stanford, California 94305, USA.
J Neurosci. 2011 May 25;31(21):7745-52. doi: 10.1523/JNEUROSCI.5425-10.2011.
Categorization is the process by which the brain segregates continuously variable stimuli into discrete groups. We report that patterns of neural population activity in the owl optic tectum (OT) categorize stimuli based on their relative strengths into "strongest" versus "other." The category boundary shifts adaptively to track changes in the absolute strength of the strongest stimulus. This population-wide categorization is mediated by the responses of a small subset of neurons. Our data constitute the first direct demonstration of explicit categorization of stimuli by a neural network based on relative stimulus strength or salience. The finding of categorization by the population code relaxes constraints on the properties of downstream decoders that might read out the location of the strongest stimulus. These results indicate that the ensemble neural code in the OT could mediate bottom-up stimulus selection for gaze and attention, a form of stimulus categorization in which the category boundary often shifts within hundreds of milliseconds.
分类是大脑将连续可变量刺激分为离散组的过程。我们报告说，猫头鹰视顶盖（OT）中的神经群体活动模式根据刺激的相对强度将其分为“最强”和“其他”。类别边界自适应地移动以跟踪最强刺激的绝对强度变化。这种全种群的分类是由一小部分神经元的反应介导的。我们的数据首次直接证明了基于相对刺激强度或显著性的神经网络对刺激的明确分类。基于群体代码的分类发现放宽了对可能读取最强刺激位置的下游解码器的属性的限制。这些结果表明，OT 中的集合神经代码可以介导自上而下的凝视和注意力选择，这是一种类别边界通常在数百毫秒内移动的刺激分类形式。
