Sensorimotor control of locomotion in complex ecological environments

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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.