Logothetis N K
Max Planck Institute for Biological Cybernetics, Tübingen, Germany.
Philos Trans R Soc Lond B Biol Sci. 1998 Nov 29;353(1377):1801-18. doi: 10.1098/rstb.1998.0333.
Figures that can be seen in more than one way are invaluable tools for the study of the neural basis of visual awareness, because such stimuli permit the dissociation of the neural responses that underlie what we perceive at any given time from those forming the sensory representation of a visual pattern. To study the former type of responses, monkeys were subjected to binocular rivalry, and the response of neurons in a number of different visual areas was studied while the animals reported their alternating percepts by pulling levers. Perception-related modulations of neural activity were found to occur to different extents in different cortical visual areas. The cells that were affected by suppression were almost exclusively binocular, and their proportion was found to increase in the higher processing stages of the visual system. The strongest correlations between neural activity and perception were observed in the visual areas of the temporal lobe. A strikingly large number of neurons in the early visual areas remained active during the perceptual suppression of the stimulus, a finding suggesting that conscious visual perception might be mediated by only a subset of the cells exhibiting stimulus selective responses. These physiological findings, together with a number of recent psychophysical studies, offer a new explanation of the phenomenon of binocular rivalry. Indeed, rivalry has long been considered to be closely linked with binocular fusion and stereopsis, and the sequences of dominance and suppression have been viewed as the result of competition between the two monocular channels. The physiological data presented here are incompatible with this interpretation. Rather than reflecting interocular competition, the rivalry is most probably between the two different central neural representations generated by the dichoptically presented stimuli. The mechanisms of rivalry are probably the same as, or very similar to, those underlying multistable perception in general, and further physiological studies might reveal much about the neural mechanisms of our perceptual organization.
能以多种方式被看到的图形是研究视觉意识神经基础的宝贵工具，因为这类刺激能使我们在任何给定时刻所感知到的神经反应与形成视觉模式感觉表征的神经反应区分开来。为了研究前一种类型的反应，让猴子经历双眼竞争，并在动物通过拉杆报告其交替感知时，研究多个不同视觉区域中神经元的反应。发现与感知相关的神经活动调制在不同的皮质视觉区域有不同程度的发生。受抑制影响的细胞几乎全是双眼的，并且发现它们的比例在视觉系统的更高处理阶段会增加。在颞叶的视觉区域观察到神经活动与感知之间最强的相关性。在对刺激的感知抑制期间，早期视觉区域中有大量神经元保持活跃，这一发现表明有意识的视觉感知可能仅由表现出刺激选择性反应的细胞子集介导。这些生理学发现，连同最近的一些心理物理学研究，为双眼竞争现象提供了一种新解释。事实上，长期以来，竞争一直被认为与双眼融合和立体视觉密切相关，优势和抑制的序列被视为两个单眼通道之间竞争的结果。这里呈现的生理学数据与这种解释不相符。竞争很可能不是反映两眼间的竞争，而是由双眼分别呈现的刺激所产生的两种不同的中枢神经表征之间的竞争。竞争机制可能与一般多稳态感知的机制相同或非常相似，进一步的生理学研究可能会揭示很多关于我们感知组织的神经机制。
