Modulation of sensory suppression: Implications for receptive field sizes in the human visual cortex
Modulation of sensory suppression: Implications for receptive field sizes in the human visual cortex
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DOI：
10.1152/jn.2001.86.3.1398
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发表时间：
2001-09-01
影响因子：
2.5
通讯作者：
Ungerleider, LG
中科院分区：
文献类型：
--
作者：
Kastner, S;De Weerd, P;Ungerleider, LG
对猴子的神经生理学研究表明，当多个视觉刺激同时出现在视野中时，它们不是独立处理的，而是以相互抑制的方式相互作用的。这表明，多个刺激竞争神经表征。与这一概念一致，我们先前在人类中发现，对于同时呈现(即，竞争)的刺激，V1以及腹侧纹外区V2、V4和Teo中的功能磁共振成像(FMRI)信号比顺序呈现(即，非竞争)的相同刺激的信号更小。在这里，我们报告了刺激之间的抑制性相互作用也存在于背侧纹外区V3A和MT，我们将这些相互作用与V1至TEO区的相互作用进行了比较。为了排除对同时和顺序呈现的刺激的反应的不同是由于瞬时开始次数的不同的可能性，我们在保持瞬时开始次数不变的实验中，测试了V4区的抑制交互作用。我们发现，上视野对刺激的fMRI反应被下视野中附近刺激的存在所抑制。此外，我们排除了这样一种可能性，即与同时呈现相比，顺序呈现的fMRI反应更大是由于外源性注意。通过让受试者在注视时数T或L的数字来暗示，这是一项需要专心完成的任务。行为测试表明，这两种情况都不影响T/L任务的执行。我们以前的发现表明，V1至Teo区附近刺激之间的抑制性相互作用与这些区域神经元的感受野(RF)大小有关。在这里，我们通过参数改变显示器中刺激之间的空间间隔来测试这一想法。显示尺寸从2x2度到7x7度，中心偏心5.5度。根据显示器大小对抑制相互作用大小的影响，我们估计偏心5.5度的RF大小是
Neurophysiological studies in monkeys show that when multiple visual stimuli appear simultaneously in the visual field, they are not processed independently, but rather interact in a mutually suppressive way. This suggests that multiple stimuli compete for neural representation. Consistent with this notion, we have previously found in humans that functional magnetic resonance imaging (fMRI) signals in V1 and ventral extrastriate areas V2, V4, and TEO are smaller for simultaneously presented (i.e., competing) stimuli than for the same stimuli presented sequentially (i.e., not competing). Here we report that suppressive interactions between stimuli are also present in dorsal extrastriate areas V3A and MT, and we compare these interactions to those in areas V1 through TEO. To exclude the possibility that the differences in responses to simultaneously and sequentially presented stimuli were due to differences in the number of transient onsets, we tested for suppressive interactions in area V4, in an experiment that held constant the number of transient onsets. We found that the fMRI response to a stimulus in the upper visual field was suppressed by the presence of nearby stimuli in the lower visual field. Further, we excluded the possibility that the greater fMRI responses to sequential compared with simultaneous presentations were due to exogeneous attentional. cueing by having our subjects count T's or L's at fixation, an attentionally demanding task. Behavioral testing demonstrated that neither condition interfered with performance of the T/L task. Our previous findings suggested that suppressive interactions among nearby stimuli in areas V1 through TEO were scaled to the receptive field (RF) sizes of neurons in those areas. Here we tested this idea by parametrically varying the spatial separation among stimuli in the display. Display sizes ranged from 2 x 2 degrees to 7 X 7 degrees and were centered at 5.5 degrees eccentricity. Based on the effects of display size on the magnitude of suppressive interactions, we estimated that RF sizes at an eccentricity of 5.5 degrees were