Laboratorium voor Neuro- en Psychofysiologie, Department of Neurosciences, KU Leuven, Belgium; Leuven Brain Institute, KU Leuven, Belgium.
Laboratorium voor Neuro- en Psychofysiologie, Department of Neurosciences, KU Leuven, Belgium; Leuven Brain Institute, KU Leuven, Belgium.
Neuroimage. 2022 Dec 1;264:119676. doi: 10.1016/j.neuroimage.2022.119676. Epub 2022 Oct 7.
In primates, faces and bodies activate distinct regions in the inferior temporal (IT) cortex and are typically studied separately. Yet, primates interact with whole agents and not with random concatenations of faces and bodies. Despite its social importance, it is still poorly understood how faces and bodies interact in IT. Here, we addressed this gap by measuring fMRI activations to whole agents and to unnatural face-body configurations in which the head was mislocated with respect to the body, and examined how these relate to the sum of the activations to their corresponding faces and bodies. First, we mapped patches in the IT of awake macaques that were activated more by images of whole monkeys compared to objects and found that these mostly overlapped with body and face patches. In a second fMRI experiment, we obtained no evidence for superadditive responses in these "monkey patches", with the activation to the monkeys being less or equal to the summed face-body activations. However, monkey patches in the anterior IT were activated more by natural compared to unnatural configurations. The stronger activations to natural configurations could not be explained by the summed face-body activations. These univariate results were supported by regression analyses in which we modeled the activations to both configurations as a weighted linear combination of the activations to the faces and bodies, showing higher regression coefficients for the natural compared to the unnatural configurations. Deeper layers of trained convolutional neural networks also contained units that responded more to natural compared to unnatural monkey configurations. Unlike the monkey fMRI patches, these units showed substantial superadditive responses to the natural configurations. Our monkey fMRI data suggest configuration-sensitive face-body interactions in anterior IT, adding to the evidence for an integrated face-body processing in the primate ventral visual stream, and open the way for mechanistic studies using single unit recordings in these patches.
在灵长类动物中，面部和身体会激活下颞叶（IT）皮质中的不同区域，通常分别进行研究。然而，灵长类动物与完整的个体进行互动，而不是与面部和身体的随机组合进行互动。尽管社交互动非常重要，但人们仍然不太了解 IT 中面部和身体是如何相互作用的。在这里，我们通过测量 fMRI 对整个个体以及不自然的面部-身体配置的激活来解决这一差距，在这些配置中，头部相对于身体的位置错位，并研究这些与相应的面部和身体激活的总和之间的关系。首先，我们绘制了清醒猕猴 IT 中的斑块，这些斑块对整个猴子的图像的激活比物体的激活更强，并发现这些斑块主要与身体和面部斑块重叠。在第二个 fMRI 实验中，我们没有发现这些“猴子斑块”中存在超加性反应的证据，即猴子的激活小于或等于面部-身体激活的总和。然而，前 IT 中的猴子斑块对自然配置的激活比对不自然配置的激活更强。与自然配置相比，更强的激活不能用面部-身体激活的总和来解释。这些单变量结果得到了回归分析的支持，我们将两种配置的激活建模为对面部和身体的激活的加权线性组合，显示自然配置的回归系数高于不自然配置的回归系数。经过训练的深层卷积神经网络的单元也对自然配置的猴子比对不自然配置的猴子有更强的反应。与猴子 fMRI 斑块不同，这些单元对自然配置表现出显著的超加性反应。我们的猴子 fMRI 数据表明，在前 IT 中存在配置敏感的面部-身体相互作用，为灵长类动物腹侧视觉流中存在整合的面部-身体处理提供了更多证据，并为这些斑块中使用单个单元记录进行机制研究开辟了道路。
