Emergence of theory of mind in young children, explored with functional MRI and Virtual Reality (VR)

将心理状态和知识归因于其他人（即他们的信仰、意图和感受），从而理解和预测他们的行为（称为“心理理论”）的能力是人类心理的一个基本特征，这种能力出现在幼儿期18个月到5岁之间（Frith等人。2005）。它对于日常社交互动和社区参与至关重要，在许多心理健康障碍中发现了心理理论的改变，并且也被认为是包括自闭症在内的神经发育状况的基础（Senju 2012）。然而，至关重要的是，作为这一关键人类技能基础的大脑处理过程目前还知之甚少，部分原因是设计合适的实验所固有的挑战，这些实验可以在典型的严格的神经成像研究设计中探索这一复杂的结构，这些研究设计也难以代表现实世界的社会互动。大脑信息的神经活动，但必须涉及行为刺激和图像采集内的限制和不自然的MRI扫描仪的环境。尽管如此，最近的研究强调了fMRI使用视频刺激和创造性分析方法提供洞察力的潜力，表明青少年和成人大脑中的相关活动发生在一个分布式区域网络中，包括内侧前额叶皮层、颞顶交界处（TPJ）、后上级颞沟（pSTS）、后扣带皮层（PCC）和楔前叶（Gao et al. 2019）。然而，由于幼儿经常难以遵循详细的指示和/或难以忍受在MRI扫描仪等陌生环境中获取数据（因此必须在睡觉时进行研究），因此对大脑及其活动如何变化以使心理理论首次出现知之甚少（Yates等人2021）。考虑到这些因素，监管团队最近开发了一种新型的MR兼容虚拟现实（VR）系统，该系统为用户提供了一个交互式模拟环境，同时躺在MRI扫描仪内（Qian等人，2021）。当使用该系统时，受试者通过放置在扫描仪孔内的MR兼容投影仪完全沉浸在视觉环境中，该投影仪直接投影到VR耳机中，并且还通过有源降噪耳机接收听觉刺激。该系统的另一个关键功能是耳机内的一对集成MRI兼容摄像机，可提供有关用户视觉行为的额外实时信息。使用强大的凝视估计算法，这不仅可以精确测量视觉注意力，还可以让受试者像在日常生活中一样使用他们的凝视作为直观和自然的交流方式（Qian等人，2021）。通过在受试者自然探索并与VR环境互动的同时获取fMRI数据，这将是一个基于fMRI的大脑活动询问的变革性新平台，其核心是克服传统僵化研究设计固有的上述限制，并可以首次详细描述幼儿大脑处理的基本理论。

The capacity to ascribe mental states and knowledge to other people (ie, their beliefs, intentions and feelings) and thus understand and predict their behaviour (known as "theory of mind") is an essential feature of the human psyche, which emerges in early childhood between 18 months of 5 years of age (Frith et al. 2005). It is essential for everyday social interaction and community participation, with altered theory of mind found in numerous mental health disorders and is also thought to underlie neurodevelopmental conditions including autism (Senju 2012). Crucially however, the brain processing that underlies this key human skill is poorly understood partly due to the challenges inherent to designing suitable experiments that can explore this complex construct within typically rigid neuroimaging study designs which also struggle to represent real-world social interact.This is particularly problematic for methods such as functional MRI (fMRI) which can provide detailed whole-brain information about neural activity but must involve behavioural stimulation and image acquisition inside the restricted and unnatural MRI scanner environment. Despite this, recent studies have highlighted the potential of fMRI to provide insight using video stimuli and creative analysis methods showing that the related activity in the adolescent and adult brain occurs a distributed network of areas that include the medial prefrontal cortex, temporal-parietal junction (TPJ), posterior superior temporal sulcus (pSTS), posterior cingulate cortex (PCC) and precuneus (Gao et al. 2019). However, as young children often struggle to follow detailed instructions and/or find it difficult to tolerate data acquisition inside an alien environment like a MRI scanner (and so must be studied when sleeping), very little is known about how the brain and its activity changes to enable theory of mind to first emerge(Yates et al. 2021). With these factors in mind, the supervisory team has recently developed a novel MR compatible virtual reality (VR) system which provides users with an interactive simulated environment whilst lying inside the MRI scanner (Qian et al. 2021). When using the system, subjects are fully immersed in a visual environment via an MR compatible projector placed inside the scanner bore which projects directly into a VR headset and also receive auditory stimulation via active noise-cancelling headphones. A further key feature of the system is a pair of integrated MRI compatible video cameras inside the headset that provide additional real-time information about the user's visual behaviour. Using a robust gaze estimation algorithm, this not only allows precise measurementof visual attention but also allows subjects to use their gaze as an intuitive and natural means of communication as they would in their daily lives (Qian et al. 2021). By simultaneously acquiring fMRI data whilst the subject naturally explores and interacts with the VR environment, there is huge potential for this to be a transformative new platform for fMRI-based interrogation of brainactivity which at its core, overcomes the aforementioned limitations inherent to traditional rigid study designs and can enable for the first time, detailed characterisation of the brain processing underlying theory of mind in young children.