Spatial perception errors do not predict pointing errors by individuals with brain lesions

We examined the relationship between errors in sensorimotor transformations (SMT) for reaching to external targets and visual and kinesthetic spatial perception of those targets by participants with damage to the posterior parietal lobule (PPL) and adjacent areas. A total of 12 participants had focal PPL lesions, 7 had with brain lesions outside the PPL, and 10 had no brain lesions. Brain lesions were due to stroke (12) or surgical resection (7). Participants made visually and kinesthetically guided pointing movements to 16 targets with the ipsilesional hand (to minimize effects of motor deficits). Head and eye movements were unrestricted. When full vision was allowed, all participants pointed accurately to visually specified targets. However, participants with PPL lesions made larger vertical plane errors than did neurologically intact control participants in visual and kinesthetic perceptual tasks and in SMT tasks (in which participants reached without vision to targets that had been visually presented). However, across all 29 participants, the size and direction of SMT errors showed low correlation with visual and kinesthetic perceptual errors. Moreover, participants with PPL lesions who made large visual and/or kinesthetic perceptual errors to individual targets also showed weak correlations with SMT errors to those targets. The results are compatible with theories that different neural pathways support perception and action for both the visual and the kinesthetic systems.