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首页> 外文期刊>Journal of Neurophysiology >Spatially specific FMRI repetition effects in human visual cortex.
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Spatially specific FMRI repetition effects in human visual cortex.

机译：在人的视觉皮层中的空间特异性FMRI重复效应。

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摘要

The functional MRI (fMRI) response to a pair of identical, successively presented stimuli can result in a smaller signal than the presentation of two nonidentical stimuli. This "repetition effect" has become a frequently used tool to make inferences about neural selectivity in specific cortical areas. However, little is known about the mechanism(s) underlying the effect. In particular, despite many successful applications of the technique in higher visual areas, repetition effects in lower visual areas [e.g., primary visual cortex (V1)] have been more difficult to characterize. One property that is well understood in early visual areas is the mapping of visual field locations to specific areas of the cortex (i.e., retinotopy). We used the retinotopic organization of V1 to activate progressively different populations of neurons in a rapid fMRI experimental design. We observed a repetition effect (reduced signal) when localized stimulus elements were repeated in identical locations. We show that this effect is spatially tuned and largely independent of both interstimulus interval (100-800 ms) and the focus of attention. Using the same timing parameters for which we observed a large effect of spatial position, we also examined the response to orientation changes and observed no effect of an orientation change on the response to repeated stimuli in V1 but significant effects in other retinotopic areas. Given these results, we discuss the possible causes of these repetition effects as well as the implications for interpreting other experiments that use this potentially powerful imaging technique.
机译：对一对相同的，连续呈现的刺激的功能性MRI（fMRI）响应所产生的信号比两个不同的刺激所呈现的信号要小。这种“重复效应”已经成为推断特定皮层区域神经选择性的常用工具。然而，对于影响该作用的机制知之甚少。特别地，尽管该技术在较高视域中有许多成功的应用，但是在较低视域中的重复效果[例如，初级视皮质（V1）]更难以表征。在早期视觉区域中很好理解的一种特性是将视野位置映射到皮质的特定区域（即，视网膜检影）。在快速的fMRI实验设计中，我们使用V1的视网膜组织来激活逐渐不同的神经元群体。当在相同位置重复局部刺激元素时，我们观察到重复效应（减少的信号）。我们表明，这种效果是在空间上调整的，并且基本上与刺激间隔（100-800 ms）和注意力焦点无关。使用相同的时序参数，我们观察到了很大的空间位置影响，我们还检查了对方向变化的响应，并没有观察到方向变化对V1中重复刺激的响应没有影响，但在其他视网膜局部区域有显着影响。鉴于这些结果，我们讨论了这些重复效应的可能原因，以及对解释使用此潜在强大成像技术的其他实验的启示。

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