Ego-centric spatial representations and their reference frames in the human brain

在不同的参照系中保持空间表征对人类行为至关重要。虽然视觉输入是在视网膜坐标中接收的，但前庭和听觉输入是以头部为中心的，而肢体动作本质上是以身体为中心的。它们需要对眼睛或头部运动保持不变，并且可能发生在视野之外。甚至我们对环境的有意识体验也是非视网膜视敏的：即使眼睛或头部的运动每秒几次地在视网膜上移动视觉场景，我们对周围视觉世界的体验也是稳定的。因此，我们周围环境的自我中心地图对于听觉、视觉和触觉等不同感官之间的整合至关重要，特别是当头部或身体运动将环境的不同部分移入或移出视野时。因此，我们对周围环境的稳定的现象体验以及与它的所有互动都是基于在自我运动过程中面对不断变化的感官输入时内部空间地图的不断更新和维护。这种表征被称为顶叶窗、自我中心表征或空间意象。在健康的人类中，我们对周围环境的自我中心地图的神经表征几乎一无所知，这些地图包括但也超出了我们的视野。在这个提议中，我们的目标是阐明人类大脑中的这种自我中心地图。特别是，我们的目标是区分头部和身体为中心的空间表示在整个人类大脑，并检查其参考框架的影响程度由头部或身体为中心的注意。这将通过对参与者的广泛培训，虚拟现实的使用以及涉及不同头部到身体方向的非传统fMRI范式来实现。我们将特别关注大脑外侧裂周围神经网络的区域，这些区域的病变与空间忽视有关，并且在前庭感觉的多感觉整合中发挥作用，但也关注参与空间编码的顶叶和颞叶区域。我们计划由一名研究人员进行一组四组实验，使用功能磁共振成像和经颅磁刺激（TMS）来探测这些区域的功能和因果关系。重要的是，这些实验的设计使得它们的结果无论其确切结果如何都是有价值的，这些结果将为人类大脑中自我中心空间表征的神经机制提供前所未有的见解，并首次使用新的功能磁共振成像方法解开头部和身体中心的神经空间表征。我们的实验问题不仅对基础认知神经科学具有重要意义，而且从长远来看，也有助于更好地理解受损大脑空间表征的神经基础，特别是与空间忽视和其他与世界互动相关的疾病。

Maintaining spatial representations in distinct reference frames is essential for human behaviour. While visual input is received in retinotopic coordinates, vestibular and auditory input are head-centred, and limb-actions are inherently body-centred. They need to be invariant to eye- or head-movements, and may occur outside the visual field of view. Even our conscious experience of the environment is non-retinotopic: we experience the visual world around us as stable even when eye- or head-movements shift the visual scene across the retina several times per second. Egocentric maps of our full surroundings are thus essential for the integration between different senses such as audition, vision, and touch, especially when head- or body-movements shift different parts of the environment in- and out of the field of view. The stable phenomenal experience of our surrounding as well as all interactions with it are thus based on the continual updating and maintenance of internal spatial maps in the face of changing sensory input during self-motion. Such representations have been referred to as parietal window, egocentric representation or spatial image. In healthy humans, almost nothing is known about neural representations of egocentric maps of our full surroundings that include, but also go beyond, our visual field of view. In this proposal we aim to shed light on such egocentric maps in the human brain. In particular we aim to distinguish between head- and body-centred spatial representations across the human brain, and to examine the extent to which their reference frames are affected by head- or body-centred attention. This will be achieved by extensive training of participants, the use of virtual reality, and an unconventional fMRI paradigm that involves distinct head-to-body orientations. We will focus especially on regions of the perisylvian network whose lesion is associated to spatial neglect and that play a role in multisensory integration with vestibular senses, but also on parietal and temporal regions involved in spatial encoding. We plan a set of four sets of experiments, carried out by one researcher, using fMRI and transcranial magnetic stimulation (TMS) to probe functional and causal involvement of these regions. Importantly, the experiments are designed such that their results will be worthwhile regardless of their exact outcome.The results will provide unprecedented insights into neural mechanisms of egocentric spatial representations in the human brain and for the first time disentangle head- from body-centred neural spatial representations using a novel fMRI imaging approach. Our experimental questions are not only significant for basic cognitive neuroscience but may in the long run also help to better understand neural underpinnings of impaired brain representations of space, in particular in relation to spatial neglect and other disorders related to the interaction with the world.