The effects of spatial attention in early human visual cortex are stimulus independent
The effects of spatial attention in early human visual cortex are stimulus independent
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DOI：
10.1167/8.10.2
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发表时间：
2008-01-01
影响因子：
1.8
通讯作者：
Murray, Scott O.
中科院分区：
文献类型：
--
作者：
Murray, Scott O.
尽管fMRI和电生理技术都表明视觉空间注意可以增加活动量，但结果却有很大差异。FMRI研究通常表明，在早期视觉区域(V1-V3)，有人值守的刺激与无人值守的刺激值相比有较大的信号增加，而先前的一些电生理学研究显示，刺激率的差异很小或没有差异。这种差异的一个可能的解释是，大多数先前的fMRI研究没有区分刺激诱发的和基线变化的对参与刺激的反应的变化。在这里，功能磁共振成像被用来分别测量刺激诱发的反应和基线偏移反应。在第一个实验中，测量了有人或无人注意的栅格刺激的对比度反应函数。结果表明，与空间注意相关的fMRI信号的增加可以通过基线漂移来解释。在第二个实验中，空间注意力被固定在一个单独的位置，该位置隔离了注意力可能由刺激引起的变化。与第一个实验一致的是，没有发现刺激诱发的变化。这些结果潜在地协调了先前fMRI研究和一些注意力神经生理学研究之间的差异，证明了早期视觉区域的空间注意效应可以由基线反应中刺激无关的变化所主导。
Although visual spatial attention has been shown to increase activity as measured with both fMRI and electrophysiological techniques, significant differences in the results have been shown. fMRI studies have routinely demonstrated large signal increases to an attended versus unattended stimulus in early visual areas (V1-V3) whereas some previous electrophysiology research has either shown very small or no differences in spike rate. One possible explanation for this discrepancy is that most previous fMRI studies have not differentiated between stimulus-evoked and baseline-shift changes in the response to an attended stimulus. Here, fMRI was used to separately measure stimulus-evoked and baseline-shift responses. In the first experiment, contrast-response functions to grating stimuli that were either attended or unattended were measured. The results show that the increases in fMRI signal associated with spatial attention are accounted for by a baseline shift. In a second experiment, spatial attention was fixed in a single location that isolated possible stimulus-evoked changes with attention. Consistent with the first experiment, no stimulus-evoked changes were found. These results potentially reconcile previous discrepant findings between fMRI studies and some neurophysiology studies of attention by demonstrating that the effects of spatial attention in early visual areas can be dominated by stimulus-independent shifts in baseline responses.