Galuske Ralf A W, Schmidt Kerstin E, Goebel Rainer, Lomber Stephen G, Payne Bertram R
Department of Neurophysiology, Max Planck Institute for Brain Research, 60528 Frankfurt am Main, Germany Europe.
Proc Natl Acad Sci U S A. 2002 Dec 24;99(26):17083-8. doi: 10.1073/pnas.242399199. Epub 2002 Dec 11.
In the primary visual cortex, neurons with similar response preferences are grouped into domains forming continuous maps of stimulus orientation and direction of movement. These properties are widely believed to result from the combination of ascending and lateral interactions in the visual system. We have tested this view by examining the influence of deactivating feedback signals descending from the visuoparietal cortex on the emergence of these response properties and representations in cat area 18. We thermally deactivated the dominant motion-processing region of the visuoparietal cortex and used optical and electrophysiological methods to assay neural activity evoked in area 18 by stimulation with moving gratings and fields of coherently moving randomly distributed dots. Feedback deactivation decreased signal strength in both orientation and direction maps and virtually abolished the global layout of direction maps, whereas the basic structure of the orientation maps was preserved. These findings could be accounted for by a selective silencing of highly direction-selective neurons and by the redirection of preferences of less selective neurons. Our data suggest that signals fed back from the visuoparietal cortex strongly contribute to the emergence of direction selectivity in early visual areas. Thus we propose that higher cortical areas have significant influence over fundamental neuronal properties as they emerge in lower areas.
在初级视皮层中,具有相似反应偏好的神经元被分组形成刺激方向和运动方向的连续图谱。人们普遍认为,这些特性是视觉系统中上行和侧向相互作用共同作用的结果。我们通过研究从视顶叶皮层下行的失活反馈信号对猫18区这些反应特性和表征出现的影响,来检验这一观点。我们通过热失活视顶叶皮层的主要运动处理区域,并使用光学和电生理方法,来检测用移动光栅和相干移动的随机分布点场刺激18区时诱发的神经活动。反馈失活降低了方向图和方向图谱中的信号强度,几乎消除了方向图谱的全局布局,而方向图的基本结构得以保留。这些发现可以通过高度方向选择性神经元的选择性沉默以及选择性较低的神经元偏好的重新定向来解释。我们的数据表明,从视顶叶皮层反馈的信号对早期视觉区域方向选择性的出现有很大贡献。因此,我们提出,更高层次的皮层区域对较低层次区域中出现的基本神经元特性有重大影响。