SOMATOSENSORY DISCRIMINATION OF SHAPE - PREDICTION OF SUCCESS IN NORMAL VOLUNTEERS AND PARKINSONIAN-PATIENTS

Tactile discrimination of macrogeometric objects in a two-alternative forced-choice procedure represents a complex task including somatosens ory and higher-order cognitive processing. The objects for somatosenso ry discrimination were rectangular parallelepipeds that differed in ob longness only. They were presented in sequential pairs to 12 normal vo lunteers and 13 parkinsonian patients. Owing to the dichotomy of the t ask, we calculated estimates of the probability of a correct answer by a binomial approach. The probability of a correct answer could be cal culated on the basis of a logistic model ensuring that the probability values lie in the interval [0, 1]. The relationship between the proba bility of a correct answer and the difference in oblongness of the obj ects could be described solely by one coefficient determined by logist ic regression. This coefficient summarized the effectiveness of the si multaneous and consecutive operations inherent in the task and allowed characterization of performances in groups and individuals.