Sensorimotor control of locomotion in complex ecological environments

在行走时避开障碍物的能力依赖于视觉，并且可能依赖于可以采取脚步声的形式的听觉线索，使得可以评估一个人自己的位移和接近的行人的位移。然而，关于接近障碍物的视觉和听觉信息如何相互作用以形成运动回避策略仍然是未知的。在一系列涉及在虚拟环境中进行的运动和功能性神经成像实验的项目中，我将研究感觉线索的整合机制，以及与受试者和回避者相关的不同因素对回避行为的影响。 目标是：（1）研究以虚拟行人（avatars）形式呈现的视觉和听觉信息在避障控制中的相互作用;（2）考察受试者性别和刺激相关因素（避障者的性别和情绪）对避障策略的影响;（3）确定参与避障控制的脑网络。 我假设：（1）障碍回避策略在生态有效的刺激配对下是最优的，但在以视觉化身和脚步声的形式显示的孤立或不一致的线索存在下就变成次优的（2）受试者的性别以及被试者所描绘的性别和情感维度对障碍回避策略有调节作用（项目2）;（3）避免虚拟行人涉及招募大脑网络，该网络包括与生物运动感知及其情感/社会维度相关的区域;当避免使用组合的视觉-听觉模态显示的化身时，（与单独的视觉模态相比），表明存在优化行人感知和回避的超模态过程（项目3）。 在项目1中，运动避障策略（策略开始，距离障碍物，等）。将被评估，同时避免在感觉模态的不同组合下显示的化身。在项目2中，将检查作为受试者性别和刺激相关因素的函数的避障策略的变化（与步态模式[中性，快乐和愤怒]相关的受试者性别和情绪）。在项目3中，将在操纵杆导航任务期间使用fMRI评估功能性大脑激活和连接，这些任务涉及避免（A）化身与圆柱体（有生命与无生命物体）和（B）在不同感觉模态下显示的化身。该计划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础知识，同时填补有关性别和感知情绪对运动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.