Pointing in 3D Space to Remembered Targets. I. Kinesthetic Versus Visual Target Presentation

Sergei V. Adamovich 1 , 2 , Mendel B. Berkinblit 1 , 2 , Olga Fookson 2 , and Howard Poizner 2 1 Institute for Problems of Information Transmission, Russian Academy of Sciences, Moscow 101447, Russia; and 2 Center for Molecular and Behavioral Neuroscience, Rutgers University, Newark, New Jersey 07102 Adamovich, Sergei V., Mendel B. Berkinblit, Olga Fookson, and Howard Poizner. Pointing in 3D space to remembered targets. I. Kinesthetic versus visual target presentation. J. Neurophysiol. 79: 2833-2846, 1998. This study investigated the influence of different modalities of target information (visual, kinesthetic) on the accuracy, kinematics, and interjoint coordination of pointing movements to remembered targets. The targets were presented by a robot arm in five locations in three-dimensional (3D) space, either as a point of light in a dark room ("visual" condition), or kinesthetically. Relative pointing accuracy in the visual compared with kinesthetic conditions was influenced by the target location: pointing errors were the largest for the visual targets most eccentric relative to the subject's head. In addition, for the two most lateral targets, the final arm positions were, on average, closer to the center than the targets in the visual condition and farther from the center than the targets in the kinesthetic conditions. This result suggests that the pattern of errors in the visual condition described elsewhere ("range effect") may derive from visual processing rather than motor planning and implementation. Two modes of kinesthetic target presentation were utilized. During "passive" kinesthetic presentation of the target, the experimenter moved the subject's relaxed arm. Alternately, in "active" kinesthetic presentation of the target, the subject actively (with minimal help from the experimenter) moved his arm. No visual feedback was allowed in either kinesthetic condition. The variability in the final fingertip position was significantly smaller in the active condition than in the passive condition. In contrast, variability in the final values of arm orientation angles did not differ significantly in the active and passive conditions. This apparent contradiction may be resolved by the fact that, for the given target location, the influence of the deviation of these angles in the given trial from their average values on the position of the fingertip tended to be mutually compensated, and this tendency was stronger in the active condition. Our analysis o