Effect of Amplitude of Reference Signal and Learning on Anisotropy in the Two-Dimensional Manual Tracking Tasks

The authors have previously reported that the human operator in the two-dimensional tracking system represented an anisotropic phenomenon, i.e., a phenomenon in which the operator exhibited different control characteristics depending upon the direction of the polarity reversal with respect to the controlled object. Furthermore, they hypothesized that the anisotropy was derived from the bilaterality of the brain. In this paper, the adequacy of the hypothesis has been evaluated by analyzing the effect of learning done by the operator and the effect of varying the amplitude of the reference signal on the anisotropic phenomenon. This leads to the discussion of a function found in the central nervous system to integrate information from different sensory modahties. Two kinds of indices obtained from the coherency function of the tracking system were used to evaluate the anisotropy. It has been revealed that the anisotropy appearing in the non-reversed (normal) components of these indices had a strong tendency to decrease as learning progressed while the anisotropy appearing in the reversed components had a weak tendency, and that the anisotropy appearing in the non-reversed components decreased as the amplitude of the reference input to the tracking system was decreased. By the use of a structural model of the information pathway in the brain, it can be explained that the above facts are consistent with the author's hypothesis.