The top down and bottom up mechanisms involved in the sudden awareness of low level sensorimotor behavior.

Motor control can be achieved in the absence of awareness, even when performed intentionally. The aim of this study was to understand the mechanisms of the sudden awareness of our own movement. This was studied in locomotion because it is an automatic behavior which can be intentionally modulated. Subjects walked continuously with the instruction to maintain either a constant walking speed (compensation condition) or constant propulsive forces (no-intervention condition); they were sometimes faced with slow variations in resistance that they had to detect. The results show that: (1) the subject remains unaware of his force increase (in compensation) or his walking velocity decrease (in no-intervention) for a long time, although these modifications go largely beyond the variability range in which he is able to intentionally control his force (in no-intervention) or his velocity (in compensation) and (2) the detection of the resistance increase occurs at the same time in both conditions. We conclude that the sudden awareness of a movement pattern produced at a low level was found to emerge from the interaction between a top down mechanism where the intentional control of goal feedback delays the aware perception of the other sensory sources and a bottom up mechanism where high level mechanisms of sensorimotor integration come into play beyond a discrepancy threshold between different sensory information.