Touch processing and motor execution both rely on two different spatial frames of reference: a representation built upon egocentric coordinates and a goal-directed representation built upon allocentric coordinates. If early visual deprivation impairs the use of an external frame of reference for touch, the question arises as to whether visual experience also affects the allocentric representation of space in the motor field. To examine this issue, early blind (EB) and sighted control participants (SC) took part in two experiments. In the first, targeting touch processing, participants were required to determine, either with their hands in parallel or crossed over the body midline, the temporal order of two tactile stimuli, one applied to each hand. Crossing the hands led to a significant decrement in performance in SC but did not affect EB, as also demonstrated by Roder and collaborators (2004), suggesting an absence of automatic external remapping of touch in this population. In the second experiment, participants were trained to perform a sequence of five fingers movements. After the training session, participants were tested on their ability to produce, with the same hand, but with the keypad turned upside down, the learned (egocentric condition) or the mirror sequence (allocentric condition). In this task, EB and SC both experienced significant transfer of motor sequence knowledge irrespective of whether the representation of the sequence was allocentric or egocentric. These results therefore demonstrate that early visual experience differentially impacts the egocentric and allocentric coding of touch and motor sequence.
