Department of Psychology, Harvard University, Cambridge, MA 02138, USA.
Department of Psychology, Harvard University, Cambridge, MA 02138, USA.
Neuroimage. 2021 Aug 15;237:118098. doi: 10.1016/j.neuroimage.2021.118098. Epub 2021 Apr 30.
In human occipitotemporal cortex, brain responses to depicted inanimate objects have a large-scale organization by real-world object size. Critically, the size of objects in the world is systematically related to behaviorally-relevant properties: small objects are often grasped and manipulated (e.g., forks), while large objects tend to be less motor-relevant (e.g., tables), though this relationship does not always have to be true (e.g., picture frames and wheelbarrows). To determine how these two dimensions interact, we measured brain activity with functional magnetic resonance imaging while participants viewed a stimulus set of small and large objects with either low or high motor-relevance. The results revealed that the size organization was evident for objects with both low and high motor-relevance; further, a motor-relevance map was also evident across both large and small objects. Targeted contrasts revealed that typical combinations (small motor-relevant vs. large non-motor-relevant) yielded more robust topographies than the atypical covariance contrast (small non-motor-relevant vs. large motor-relevant). In subsequent exploratory analyses, a factor analysis revealed that the construct of motor-relevance was better explained by two underlying factors: one more related to manipulability, and the other to whether an object moves or is stable. The factor related to manipulability better explained responses in lateral small-object preferring regions, while the factor related to object stability (lack of movement) better explained responses in ventromedial large-object preferring regions. Taken together, these results reveal that the structure of neural responses to objects of different sizes further reflect behavior-relevant properties of manipulability and stability, and contribute to a deeper understanding of some of the factors that help the large-scale organization of object representation in high-level visual cortex.
在人类枕颞叶皮质中，对描绘的无生命物体的大脑反应具有按真实世界物体大小组织的大规模结构。至关重要的是，世界上物体的大小与行为相关的特性系统相关：小物体通常被抓取和操纵（例如，叉子），而大物体往往与运动相关度较低（例如，桌子），尽管这种关系并不总是正确的（例如，画框和独轮手推车）。为了确定这两个维度如何相互作用，我们使用功能磁共振成像测量了参与者在观看具有低或高运动相关性的小物体和大物体的刺激集时的大脑活动。结果表明，物体的大小组织对于具有低和高运动相关性的物体都是明显的；此外，在大物体和小物体上都存在运动相关性图。有针对性的对比表明，典型的组合（小运动相关与大非运动相关）比非典型协方差对比（小非运动相关与大运动相关）产生更强大的地形。在随后的探索性分析中，因子分析表明，运动相关性的结构由两个潜在因素更好地解释：一个与可操作性更相关，另一个与物体是否移动或稳定相关。与可操作性相关的因素更好地解释了侧部小物体偏好区域的反应，而与物体稳定性（缺乏运动）相关的因素更好地解释了腹内侧大物体偏好区域的反应。总之，这些结果表明，不同大小物体的神经反应结构进一步反映了可操作性和稳定性等行为相关特性，并有助于更深入地了解有助于物体在高级视觉皮层中大规模组织的一些因素。
