The Brain and Mind Institute, University of Western Ontario, London, ON, Canada N6A 5B7.
J Cogn Neurosci. 2012 Apr;24(4):905-14. doi: 10.1162/jocn_a_00190. Epub 2012 Jan 5.
We used fMRI to study figure-ground representation and its decay in primary visual cortex (V1). Human observers viewed a motion-defined figure that gradually became camouflaged by a cluttered background after it stopped moving. V1 showed positive fMRI responses corresponding to the moving figure and negative fMRI responses corresponding to the static background. This positive-negative delineation of V1 "figure" and "background" fMRI responses defined a retinotopically organized figure-ground representation that persisted after the figure stopped moving but eventually decayed. The temporal dynamics of V1 "figure" and "background" fMRI responses differed substantially. Positive "figure" responses continued to increase for several seconds after the figure stopped moving and remained elevated after the figure had disappeared. We propose that the sustained positive V1 "figure" fMRI responses reflected both persistent figure-ground representation and sustained attention to the location of the figure after its disappearance, as did subjects' reports of persistence. The decreasing "background" fMRI responses were relatively shorter-lived and less biased by spatial attention. Our results show that the transition from a vivid figure-ground percept to its disappearance corresponds to the concurrent decay of figure enhancement and background suppression in V1, both of which play a role in form-based perceptual memory.
我们使用 fMRI 研究了初级视觉皮层 (V1) 中的图形-背景表示及其衰减。人类观察者观看一个由运动定义的图形，当它停止运动后，逐渐被杂乱的背景掩盖。V1 对运动的图形显示出正的 fMRI 响应，对静止的背景显示出负的 fMRI 响应。V1 的这种正-负的“图形”和“背景” fMRI 响应的划分定义了一个在图形停止运动后仍然存在但最终衰减的具有视网膜组织的图形-背景表示。V1 的“图形”和“背景” fMRI 响应的时间动态有很大的不同。在图形停止运动后，正的“图形”响应继续增加数秒，并在图形消失后仍保持升高。我们提出，持续的 V1“图形” fMRI 响应既反映了图形-背景表示的持续，也反映了在图形消失后对其位置的持续注意，这与被试报告的持续性相符。负的“背景” fMRI 响应持续时间相对较短，且受空间注意的影响较小。我们的结果表明，从生动的图形-背景知觉到其消失，对应于 V1 中图形增强和背景抑制的同时衰减，两者都在基于形状的感知记忆中起作用。
