Neural mechanisms of spatial selective attention in areas V1, V2, and V4 of macaque visual cortex
Neural mechanisms of spatial selective attention in areas V1, V2, and V4 of macaque visual cortex
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DOI：
10.1152/jn.1997.77.1.24
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发表时间：
1997-01-01
影响因子：
2.5
通讯作者：
Desimone, R
中科院分区：
文献类型：
--
作者：
Luck, SJ;Chelazzi, L;Desimone, R
许多层外视觉皮层的神经元具有较大的接受野，这可能会导致重大的计算问题，当多个刺激落在一个单一的持有。先前的研究表明，当多个刺激落在细胞的接受野中时，它们会以一种偏向于参与刺激的方式竞争细胞的反应。在本研究中，我们使用一种行为范式，将注意力引导到两个刺激位置之一，研究了猕猴在区域VI、V2和V4中注意力的作用。当两种刺激同时出现在细胞的感受野中时（这只能在V2和V4区域完成），我们发现细胞的反应受到两种刺激中的哪一种的强烈影响。当被注意和被忽略的刺激顺序出现而不是同时出现时，这种注意效应的大小会减小。此外，当两种刺激中只有一种位于接受区时，这些区域的影响变得非常微弱和不一致。因此，当两个或多个同时的刺激竞争进入神经元的接受野时，注意力主要调节感觉反应。就像在V2和V4区域一样，当只有一个单一的刺激在接受区时，注意不会调节V1区域的感觉反应。此外，该区域的小感受野阻碍了在接受持有内同时呈现被注意和被忽视的刺激，因此无法确定在导致V2和V4区域一致的注意效应的条件下是否会观察到注意效应。当注意力被引导到感受野的内部而不是外部时，即使在没有刺激的情况下，V2和V4区域的自发放电率也会高出30-40%。自发放电的频率也根据被参与的感受野的特定位置而变化。自发活动的这些变化可能反映了一个自上而下的信号，该信号使反应偏向于参与地点的刺激。
Many neurons in extrastriate visual cortex have large receptive fields, and this may lead to significant computational problems whenever multiple stimuli fall within a single held. Previous studies have suggested that when multiple stimuli fall within a cell's receptive field, they compete for the cell's response in a manner that can be biased in favor of attended stimuli. In the present study we examined this role of attention in areas VI, V2, and V4 of macaque monkeys with the use of a behavioral paradigm in which attention was directed to one of two stimulus locations. When two stimuli were presented simultaneously inside the cell's receptive field (which could be accomplished only in areas V2 and V4), we found that the cell's response was strongly influenced by which of the two stimuli was attended. The size of this attention effect was reduced when the attended and ignored stimuli were presented sequentially rather than simultaneously. In addition, the effects became very weak and inconsistent in these areas when only one of the two stimuli was located inside the receptive held. Attention thus modulated sensory responses primarily when two or more simultaneous stimuli competed for access to a neuron's receptive field. As in areas V2 and V4, attention did not modulate sensory responses in area V1 when only a single stimulus was inside the receptive held. In addition, the small receptive fields in this area precluded the simultaneous presentation of attended and ignored stimuli inside the receptive held, making it impossible to determine whether attention effects would be observed under the conditions that led to consistent attention effects in areas V2 and V4. Spontaneous firing rates in areas V2 and V4 were found to be 30-40% higher when attention was directed inside rather than outside the receptive field, even when no stimulus was present in the receptive held. Spontaneous firing rates also varied according to the particular location within the receptive field that was attended. These shifts in spontaneous activity may reflect a top-down signal that biases responses in favor of stimuli at the attended location.