Center for Neural Science, New York University, New York, New York 10003, USA.
J Neurosci. 2013 Jun 12;33(24):9879-89. doi: 10.1523/JNEUROSCI.0500-12.2013.
To locate visual objects, the brain combines information about retinal location and direction of gaze. Studies in monkeys have demonstrated that eye position modulates the gain of visual signals with "gain fields," so that single neurons represent both retinotopic location and eye position. We wished to know whether eye position and retinotopic stimulus location are both represented in human visual cortex. Using functional magnetic resonance imaging, we measured separately for each of several different gaze positions cortical responses to stimuli that varied periodically in retinal locus. Visually evoked responses were periodic following the periodic retinotopic stimulation. Only the response amplitudes depended on eye position; response phases were indistinguishable across eye positions. We used multivoxel pattern analysis to decode eye position from the spatial pattern of response amplitudes. The decoder reliably discriminated eye position in five of the early visual cortical areas by taking advantage of a spatially heterogeneous eye position-dependent modulation of cortical activity. We conclude that responses in retinotopically organized visual cortical areas are modulated by gain fields qualitatively similar to those previously observed neurophysiologically.
为了定位视觉物体，大脑结合了关于视网膜位置和注视方向的信息。在猴子身上的研究表明，眼位置通过“增益场”调节视觉信号的增益，使得单个神经元既代表视网膜位置又代表眼位置。我们想知道眼位置和视网膜刺激位置是否都在人类视觉皮层中得到表示。使用功能磁共振成像，我们分别测量了几个不同注视位置的皮质对周期性变化的视网膜位置刺激的反应。视觉诱发反应在周期性视网膜刺激后呈周期性。只有反应幅度取决于眼位置;在不同的眼位置，反应阶段无法区分。我们使用多体素模式分析从响应幅度的空间模式中解码眼位置。该解码器通过利用皮质活动的空间异质性的、依赖于眼位置的调制，可靠地从五个早期视觉皮层区域的空间模式中区分眼位置。我们得出的结论是，在具有视网膜拓扑结构的视觉皮层区域中的反应被增益场调制，其性质与以前在神经生理学中观察到的增益场相似。
