CHARACTERISTICS OF TARGET-REACHING IN CATS .1. INDIVIDUAL-DIFFERENCESAND INTRAINDIVIDUAL CONSTANCY

Trajectory formation of unrestrained forelimb target-reaching was inve stigated in six cats. A Selspot-like recording system was used for thr ee-dimensional recording of the position of the wrist every 3 ms with the aid of two cameras detecting infrared light emitted from diodes ta ped to the wrist. These measurements allowed reconstruction of movemen t paths in the horizontal and sagittal planes and velocity profiles in the direction of the cartesian x, y and z co-ordinates. Horizontal mo vement paths were smoothly curved, segmented or almost linear. Sagitta l movement paths were sigmoid. The net velocity profile was usually be ll-shaped with longer deceleration than acceleration, but for some slo w movements the velocity profile had a plateau. When the net velocity profile was bell-shaped, the averaged sagittal movement paths and norm alized x (protraction) and z (lifting) velocity profiles were virtuall y superimposable for fast and slow movements: thus, movement speed was changed by parallel scaling of protraction and lifting. Comparison of movement paths and velocity profiles amongst the different cats revea led considerable differences. The x profile was unimodal in one cat an d double peaked in five cats: the second component was pronounced in t wo cats and small in the other three. The z profile was unimodal and, except for one cat, it had later onset and summit than the first compo nent of the x profile. In contrast to the interindividual differences, there was a high degree of intraindividual constancy over 6-12 months . It is postulated that the interindividual variability depends on cha nce differences established early during learning of the task and that the imprinted pattern remains, resulting in intra-individual constanc y.