Gawne Timothy J, Martin Julie M
Department of Physiological Optics, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.
J Neurophysiol. 2002 Nov;88(5):2178-86. doi: 10.1152/jn.00151.200.
Our visual experience constitutes an unending chain of transient events, including those caused by saccadic eye movements, by blinks, and by localized or global changes in the external world. The categorical perception of objects is maintained across different classes of transient events, suggesting that the neural circuitry underlying visual perception responds to different transient events in a similar manner. However, different sorts of transients do have different perceptual impacts: for example, the sudden changes in a scene due to a saccade or a blink do not disturb our perceptual continuity of a visual scene as much as an external change does. We recorded the responses of 103 single visual cortical neurons in two rhesus monkeys (V1: n = 38, V2: n = 19, V3V/VP: n = 30, V4V: n = 16) to the onset and offset of a visual stimulus that was elicited by four different conditions: 1) stimulus flashed on and off while the eyes remain fixed; 2) stimulus turned on and off along with the entire scene (external darkening); 3) stimulus constant, onset and offset induced by rapid saccadic eye movements; and 4) offset induced by an eyeblink. For most neurons the onset and offset of a visual stimulus elicited qualitatively similar responses regardless of condition. We found no systematic effect of different conditions across the neuronal population. Previously we have shown that when the visual scene is occluded by a blink V1 neuronal firing declines in a similar manner as when the external scene is darkened and the eyes left open. Here we show that this is also the case in V2, V3V/VP, and V4V. However, for a substantial minority of neurons, the response varied strongly as a function of the transient event. This overall pattern was the same in all four cortical areas studied here. We hypothesize that most neurons in visual cortex constitute a passive "filter bank", analyzing the scene for specific details regardless of condition. However, there are neurons that respond in a qualitatively different manner depending on how a stimulus is presented, and we hypothesize that these signals may be important for determining the perceptual salience of a visual event.
我们的视觉体验构成了一系列无休止的短暂事件，包括由眼球快速运动、眨眼以及外部世界的局部或整体变化所引起的事件。对物体的分类感知在不同类型的短暂事件中得以保持，这表明视觉感知背后的神经回路以相似的方式对不同的短暂事件做出反应。然而，不同类型的瞬变确实会产生不同的感知影响：例如，由眼球快速运动或眨眼引起的场景突然变化，对视觉场景感知连续性的干扰程度不如外部变化那么大。我们记录了两只恒河猴的103个单视觉皮层神经元（V1区：n = 38，V2区：n = 19，V3V/VP区：n = 30，V4V区：n = 16）对由四种不同条件引发的视觉刺激的起始和终止的反应：1）眼睛保持固定时刺激闪烁开启和关闭；2）刺激与整个场景一起开启和关闭（外部变暗）；3）刺激恒定，由快速眼球运动引发起始和终止；4）由眨眼引发终止。对于大多数神经元而言，无论处于何种条件，视觉刺激的起始和终止都会引发性质相似的反应。我们在整个神经元群体中未发现不同条件的系统性影响。此前我们已经表明，当视觉场景被眨眼遮挡时，V1区神经元的放电活动与外部场景变暗且眼睛睁开时的下降方式相似。在此我们表明，V2区、V3V/VP区和V4V区也是如此。然而，对于相当少数的神经元，其反应会根据短暂事件而强烈变化。在本文研究的所有四个皮层区域中，这种总体模式都是相同的。我们推测，视觉皮层中的大多数神经元构成一个被动的“滤波器组”，无论条件如何，都会分析场景中的特定细节。然而，存在一些神经元会根据刺激的呈现方式做出性质不同的反应，我们推测这些信号对于确定视觉事件的感知显著性可能很重要。
