Azizi Amir Hossein, Pusch Roland, Koenen Charlotte, Klatt Sebastian, Bröker Franziska, Thiele Samuel, Kellermann Janosch, Güntürkün Onur, Cheng Sen
Institute for Neural Computation, Ruhr-University Bochum, 44801 Bochum, Germany.
Biopsychology, Institute of Cognitive Neuroscience, Faculty of Psychology, Ruhr-University Bochum, 44801 Bochum, Germany.
Behav Brain Res. 2019 Jan 1;356:423-434. doi: 10.1016/j.bbr.2018.05.014. Epub 2018 Jun 6.
Recognizing and categorizing visual stimuli are cognitive functions vital for survival, and an important feature of visual systems in primates as well as in birds. Visual stimuli are processed along the ventral visual pathway. At every stage in the hierarchy, neurons respond selectively to more complex features, transforming the population representation of the stimuli. It is therefore easier to read-out category information in higher visual areas. While explicit category representations have been observed in the primate brain, less is known on equivalent processes in the avian brain. Even though their brain anatomies are radically different, it has been hypothesized that visual object representations are comparable across mammals and birds. In the present study, we investigated category representations in the pigeon visual forebrain using recordings from single cells responding to photographs of real-world objects. Using a linear classifier, we found that the population activity in the visual associative area mesopallium ventrolaterale (MVL) distinguishes between animate and inanimate objects, although this distinction is not required by the task. By contrast, a population of cells in the entopallium, a region that is lower in the hierarchy of visual areas and that is related to the primate extrastriate cortex, lacked this information. A model that pools responses of simple cells, which function as edge detectors, can account for the animate vs. inanimate categorization in the MVL, but performance in the model is based on different features than in MVL. Therefore, processing in MVL cells is very likely more abstract than simple computations on the output of edge detectors.
识别和分类视觉刺激是对生存至关重要的认知功能，也是灵长类动物和鸟类视觉系统的一个重要特征。视觉刺激沿着腹侧视觉通路进行处理。在层次结构的每个阶段，神经元对更复杂的特征进行选择性响应，从而改变刺激的群体表征。因此，在更高的视觉区域更容易读出类别信息。虽然在灵长类动物大脑中已经观察到明确的类别表征，但对于鸟类大脑中的等效过程了解较少。尽管它们的大脑解剖结构截然不同，但据推测，视觉对象表征在哺乳动物和鸟类中是可比的。在本研究中，我们使用对现实世界物体照片做出反应的单细胞记录，研究了鸽子视觉前脑的类别表征。使用线性分类器，我们发现视觉联想区域腹外侧中脑皮质（MVL）中的群体活动能够区分有生命和无生命的物体，尽管该任务并不需要这种区分。相比之下，位于视觉区域层次结构较低且与灵长类动物纹外皮层相关的内皮层中的一群细胞则缺乏此信息。一个汇集起充当边缘检测器的简单细胞反应的模型，可以解释MVL中有生命与无生命的分类，但该模型的性能基于与MVL不同的特征。因此，MVL细胞中的处理很可能比边缘检测器输出的简单计算更为抽象。
