解码视觉皮层中动态遮挡物体的信息。

Decoding information about dynamically occluded objects in visual cortex.

作者信息

Erlikhman Gennady, Caplovitz Gideon P

机构信息

Department of Psychology, University of Nevada, Reno, USA.

Department of Psychology, University of Nevada, Reno, USA.

出版信息

Neuroimage. 2017 Feb 1;146:778-788. doi: 10.1016/j.neuroimage.2016.09.024. Epub 2016 Sep 20.

Abstract

During dynamic occlusion, an object passes behind an occluding surface and then later reappears. Even when completely occluded from view, such objects are experienced as continuing to exist or persist behind the occluder even though they are no longer visible. The contents and neural basis of this persistent representation remain poorly understood. Questions remain as to whether there is information maintained about the object itself (i.e. its shape or identity) or non-object-specific information such as its position or velocity as it is tracked behind an occluder, as well as which areas of visual cortex represent such information. Recent studies have found that early visual cortex is activated by "invisible" objects during visual imagery and by unstimulated regions along the path of apparent motion, suggesting that some properties of dynamically occluded objects may also be neurally represented in early visual cortex. We applied functional magnetic resonance imaging in human subjects to examine representations within visual cortex during dynamic occlusion. For gradually occluded, but not for instantly disappearing objects, there was an increase in activity in early visual cortex (V1, V2, and V3). This activity was spatially-specific, corresponding to the occluded location in the visual field. However, the activity did not encode enough information about object identity to discriminate between different kinds of occluded objects (circles vs. stars) using MVPA. In contrast, object identity could be decoded in spatially-specific subregions of higher-order, topographically organized areas such as ventral, lateral, and temporal occipital areas (VO, LO, and TO) as well as the functionally defined LOC and hMT+. These results suggest that early visual cortex may only represent the dynamically occluded object's position or motion path, while later visual areas represent object-specific information.

摘要

在动态遮挡过程中,一个物体从遮挡表面后方经过,随后再次出现。即使完全被遮挡而看不见,这些物体仍被感知为在遮挡物后方持续存在,尽管它们已不再可见。这种持续表征的内容和神经基础仍知之甚少。关于在遮挡物后方追踪物体时,是保留了关于物体本身的信息(即其形状或身份),还是保留了非物体特定信息(如位置或速度),以及视觉皮层的哪些区域表征此类信息,这些问题依然存在。最近的研究发现,早期视觉皮层在视觉表象期间会被“不可见”物体激活,并且在明显运动路径上未受刺激的区域也会被激活,这表明动态遮挡物体的某些属性可能也在早期视觉皮层中得到神经表征。我们对人类受试者应用功能磁共振成像来检查动态遮挡期间视觉皮层内的表征。对于逐渐被遮挡但并非瞬间消失的物体,早期视觉皮层(V1、V2和V3)的活动增加。这种活动具有空间特异性,与视野中被遮挡的位置相对应。然而,使用多变量模式分析(MVPA)时,这种活动并未编码足够的关于物体身份的信息来区分不同类型的被遮挡物体(圆形与星形)。相比之下,物体身份可以在高阶、具有地形组织的区域(如腹侧、外侧和颞枕叶区域(VO、LO和TO)以及功能定义的LOC和hMT +)的空间特异性子区域中解码。这些结果表明,早期视觉皮层可能仅表征动态遮挡物体的位置或运动路径,而后期视觉区域则表征物体特定信息。

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