Perception and action are two interacting parts of a unique system, interfaced by embodied dynamic simulation of reality (Berthoz, 1992). Human brain's prefrontal gyrus contains the mirror neuron system, reacting the same during perception and realization of a given motor action (Rizzolatti and Craighero, 2004; Kilner, 2009). Consequently, if to observe is needed to reproduce, then imitating can be one foundation of learning. Post-stroke patients have proprioceptive deficits affecting the motor output (Smith et al., 1983). Optical biofeedback enabled patients to use vision as the main perceptive input during rehabilitation (Huang, 2006). We intended to verify if perception of a modified self, influences motor behavior and if this can be used to the benefit of post-stroke gait rehabilitation.

As a control for effectiveness of avatar on motor behavior, 10 healthy subjects walked on a treadmill surrounded by a panoramic screen with immersive virtual reality. Eighteen post-stroke patients performed a rehabilitation with the same hardware conditions. We created a virtual “self” for the subjects and made them watch their own real-time and potentially mismatching avatar with modified knee flexion. Kinematic data were collected with 10 infrared cameras and processed with the Plug-in-Gait model. One-way Anova-s were performed to compare independent groups.

Healthy subjects knee flexion was significantly increased when avatar's one was increased by 35 degrees. Patients with increased avatar improved significantly their knee flexion by 5.35 degrees.

Using increased avatar allows to interfere with the action-perception loop, and make healthy and affected subjects bend their knee more than usual. We expect mirror neuron system to be involved in this spontaneous imitation mechanism. Experimentation dedicated to brain afferents is considered using an electroencephalogram to determine an optimum angle with stroke patients to generalize use of enhanced feedback during rehabilitation.