Huang Jie, Xiang Ming, Cao Yue
Department of Radiology, Michigan State University, East Lansing, MI 48824, USA.
Neuroimage. 2006 Jul 15;31(4):1693-9. doi: 10.1016/j.neuroimage.2006.02.020. Epub 2006 Apr 5.
The perception of a brief visual target stimulus can be affected by another visual mask stimulus immediately preceding or following the target. The link of this visual masking illusion, with visual cortical activation, offers insights into the neural mechanisms for visual perception. The present study investigated the association of the visibility of a target with cortical activation in humans using psychophysical testing and functional magnetic resonance imaging (fMRI). A visual masking protocol that was suitable for an fMRI study was developed. The event-related fMRI was used to measure activation in primary visual cortex (V1) during visual masking and unmasking stimulation. We found that the visibility of the target stimulus was reduced in the masking condition, due to the presence of mask stimuli, but not in the unmasking condition. We also found that the activation in V1 was modulated by the temporal separation of the mask stimuli from the target and was associated with the visibility of the target that was recorded during psychophysical testing and fMRI. These findings are consistent with what has been observed in the primate visual cortex of monkeys, i.e., the transient on-response and after-discharge of V1 neurons to the target stimulus were suppressed by forward and backward mask stimuli, respectively.
对短暂视觉目标刺激的感知会受到紧接在目标之前或之后的另一个视觉掩蔽刺激的影响。这种视觉掩蔽错觉与视觉皮层激活之间的联系，为视觉感知的神经机制提供了见解。本研究使用心理物理学测试和功能磁共振成像（fMRI）来探究人类中目标的可见性与皮层激活之间的关联。开发了一种适用于fMRI研究的视觉掩蔽方案。采用事件相关fMRI来测量在视觉掩蔽和非掩蔽刺激期间初级视觉皮层（V1）的激活情况。我们发现，由于掩蔽刺激的存在，在掩蔽条件下目标刺激的可见性降低，但在非掩蔽条件下则不然。我们还发现，V1中的激活受到掩蔽刺激与目标之间时间间隔的调节，并且与在心理物理学测试和fMRI期间记录的目标可见性相关。这些发现与在猴子的灵长类视觉皮层中所观察到的情况一致，即V1神经元对目标刺激分别被前向和后向掩蔽刺激抑制了瞬态开启反应和后放电。
