Early visual experience affects memorization and spatial representation of proprioceptive targets.

Five subjects who had been blind from an early age and five age-matched blindfolded sighted subjects were engaged in a spatial memory task. Locations to be memorized were presented on a sagittal plane by passive positioning of the left index finger. A go signal for matching the target location with the right index finger was provided 0 or 8 s after left hand positioning. Constant errors in amplitude and direction of movement and pointing distribution observed after the longer delay differed across groups. Pointing variability was higher in the blindfolded sighted group. In addition, the main axis of pointing distributions obtained in the blindfolded sighted group were aligned with the target array for the 8 s but not the 0 s delay. By contrast, the main axis tended to be aligned with movement direction for blind subjects for both delays. These results suggest that memorizing a proprioceptively defined target may involve distinct spatial representations according to delay and to early visual experience.