Our Faces in the Dog's Brain: Functional Imaging Reveals Temporal Cortex Activation during Perception of Human Faces

Dogs have a rich social relationship with humans. One fundamental aspect of it is how dogs pay close attention to human faces in order to guide their behavior, for example, by recognizing their owner and his/her emotional state using visual cues. It is well known that humans have specific brain regions for the processing of other human faces, yet it is unclear how dogs’ brains process human faces. For this reason, our study focuses on describing the brain correlates of perception of human faces in dogs using functional magnetic resonance imaging (fMRI). We trained seven domestic dogs to remain awake, still and unrestrained inside an MRI scanner. We used a visual stimulation paradigm with block design to compare activity elicited by human faces against everyday objects. Brain activity related to the perception of faces changed significantly in several brain regions, but mainly in the bilateral temporal cortex. The opposite contrast (i.e., everyday objects against human faces) showed no significant brain activity change. The temporal cortex is part of the ventral visual pathway, and our results are consistent with reports in other species like primates and sheep, that suggest a high degree of evolutionary conservation of this pathway for face processing. This study introduces the temporal cortex as candidate to process human faces, a pillar of social cognition in dogs.

犬类与人类之间存在着丰富的社会互动关系。其中一项核心特征为，犬类会密切关注人类面部以调控自身行为，例如通过视觉线索识别主人及其情绪状态。众所周知，人类拥有专门处理同类面部信息的特定脑区，但目前学界仍不清楚犬类大脑如何处理人类面部。为此，本研究借助功能磁共振成像（functional magnetic resonance imaging，简称fMRI）技术，旨在阐明犬类感知人类面部时的脑活动关联特征。我们训练了7只家犬，使其能够在磁共振成像扫描仪中保持清醒、静止且无束缚的状态。本研究采用组块设计的视觉刺激范式，对比人类面部与日常物品所诱发的脑活动差异。结果显示，在多个脑区中，与面部感知相关的脑活动均发生了显著变化，其中以双侧颞叶皮层最为显著。反之，即对比日常物品与人类面部的对照条件，则未观察到显著的脑活动变化。颞叶皮层属于腹侧视觉通路的组成部分，本研究结果与灵长类、绵羊等其他物种的相关报道相符——这些研究均表明，该通路用于面部处理的功能在进化过程中具有高度保守性。本研究首次将颞叶皮层确立为犬类处理人类面部信息的候选脑区，而这一脑区亦是犬类社会认知的核心支柱之一。