Silver Michael A, Ress David, Heeger David J
School of Optometry, University of California-Berkeley, Berkeley, CA 94720-2020, USA.
J Neurophysiol. 2007 Jan;97(1):229-37. doi: 10.1152/jn.00677.2006. Epub 2006 Sep 13.
Attention is thought to enhance perceptual performance at attended locations through top-down attention signals that modulate activity in visual cortex. Here, we show that activity in early visual cortex is sustained during maintenance of attention in the absence of visual stimulation. We used functional magnetic resonance imaging (fMRI) to measure activity in visual cortex while human subjects performed a visual detection task in which a variable-duration delay period preceded target presentation. Portions of cortical areas V1, V2, and V3 representing the attended part of the visual field exhibited sustained increases in activity throughout the delay period. Portions of these cortical areas representing peripheral, unattended parts of the visual field displayed sustained decreases in activity. The data were well fit by a model that assumed the sustained neural activity was constant in amplitude over a time period equal to that of the actual delay period for each trial. These results demonstrate that sustained attention responses are present in early visual cortex (including primary visual cortex), in the absence of a visual stimulus, and that these responses correlate with the allocation of visuospatial attention in both the spatial and temporal domains.
注意力被认为是通过自上而下的注意力信号来增强在被关注位置的感知表现，这些信号会调节视觉皮层的活动。在此，我们表明，在没有视觉刺激的情况下，早期视觉皮层的活动在注意力维持期间会持续。我们使用功能磁共振成像（fMRI）来测量视觉皮层的活动，当时人类受试者执行一项视觉检测任务，在目标呈现之前有一个可变持续时间的延迟期。代表视野中被关注部分的皮层区域V1、V2和V3的部分在整个延迟期内活动持续增加。这些皮层区域中代表视野外周、未被关注部分的部分活动持续减少。数据与一个模型拟合得很好，该模型假设在等于每个试验实际延迟期的时间段内，持续的神经活动在幅度上是恒定的。这些结果表明，在没有视觉刺激的情况下，早期视觉皮层（包括初级视觉皮层）存在持续的注意力反应，并且这些反应在空间和时间领域都与视觉空间注意力的分配相关。
