Sensorimotor control of locomotion in complex ecological environments

行走时避开障碍物的能力依赖于视觉，也可能依赖于可以采取脚步声形式的听觉线索，这样就可以评估自己和走近的行人(S)的位移。然而，关于接近的障碍物的视觉和听觉信息如何相互作用来形成运动回避策略仍是未知的。在一系列项目中，包括在虚拟环境中进行的运动和功能神经成像实验，我将研究感觉线索整合的机制，以及与受试者和干扰者相关的不同因素对回避行为的影响。 目的是：(1)研究以虚拟行人(化身)形式呈现的视觉和听觉信息在避障控制中的交互作用；(2)考察受试者性别和刺激相关因素(干扰者的性别和情绪)对避障策略的影响；(3)确定参与避障控制的大脑网络。 我假设：(1)在生态有效的刺激组合下，避障策略是优化的，但在以视觉化身和脚步声的形式显示的孤立或不协调的线索存在的情况下，避障策略变得次优(项目1)；(2)受试者的性别以及干扰者所描绘的性别和情感维度调节了避障策略(项目2)；(3)虚拟行人的回避涉及到大脑网络的招募，该网络由与生物运动的感知及其情绪/社会维度相关的区域组成；在避免使用视觉-听觉组合模式显示的化身时，观察到更强的激活(与单独使用视觉模式相比)，这表明存在优化行人感知和回避的超模式过程(项目3)。 在项目1中，移动避障策略(策略开始、与障碍物的距离等)将在避免在不同感觉通道组合下显示的化身的同时进行评估。在项目2中，将考察受试者性别和刺激相关因素(干扰者的性别和与步态模式[中性、快乐和愤怒]相关的情绪)对避障策略的影响。在项目3中，将在操纵杆导航任务中使用功能磁共振成像来评估大脑的功能激活和连通性，这些任务涉及避免(A)化身与圆柱体(有生命的与无生命的物体)和(B)在不同感官模式下显示的化身。本课程将提供有关感觉线索整合机制以及它们如何调节运动行为的基本知识，同时填补关于性别和感知情绪对运动行为影响的巨大知识空白。

The ability to avoid obstacles while walking relies on vision, and possibly on auditory cues which can take the form of footstep sounds, such that one’s own displacement and that of the approaching pedestrian(s) can be assessed. How the visual and auditory information about an approaching obstacle may interact to shape locomotor avoidance strategies, however, remains unknown. In a series of projects that involve locomotor and functional neuroimaging experiments performed in a virtual environment, I will investigate the mechanisms of integration of sensory cues, as well as the influence of different factors related to the subject and the interferer on the avoidance behaviour. Objectives are to: (1) Investigate the interacting role of visual and auditory information presented in the form of virtual pedestrians (avatars) in the control of obstacle avoidance; (2) Examine the influence of subject gender and stimulus-related factors (gender and emotion of interferer) on obstacle avoidance strategies and; (3) Determine the brain networks that are involved in the control of obstacle avoidance. I hypothesize that: (1) Obstacle avoidance strategies are optimized under ecologically valid stimulus pairing, but become sub-optimal in the presence of isolated or incongruent cues displayed in the form of visual avatars and footstep sounds (Project 1); (2) The subjects’ gender, as well as the gender and emotional dimension portrayed by the interferer, modulate obstacle avoidance strategies (Project 2); (3) The avoidance of virtual pedestrians involves the recruitment of a brain network that comprises of areas associated to the perception of biological motion and its emotional/social dimension; stronger activations are observed when avoiding avatars displayed using combined visual-auditory modalities (compared to visual modality alone), suggesting the presence of supramodal processes that optimize the perception and avoidance of pedestrians (Project 3). In Project 1, locomotor obstacle avoidance strategies (onset of strategy, distance from obstacle, etc.) will be assessed while avoiding avatars displayed under different combinations of sensory modality. In Project 2, changes in obstacle avoidance strategies as a function of subject gender and stimulus-related factors (interferer’s gender and emotion associated with the gait pattern [neutral, happy & angry]) will be examined. In Project 3, functional brain activation and connectivity will be assessed using fMRI during joystick navigation tasks that involve the avoidance of (A) avatars vs. cylinders (animate vs. inanimate objects) and (B) avatars displayed under different sensory modalities. This program will provide fundamental knowledge on mechanisms of integration of sensory cues and on how they modulate locomotor behaviour, while filling a large knowledge gap concerning the influence of gender and perceived emotions on locomotion.