Different recovery of a skilled movement after destruction of the caudate nucleus in rats with right- or left-forelimb preference]

Recovery of the motor skill of taking a sunflower seed from a tube after the electrolytic destruction of the caudate nucleus was studied in Wistar rats with left- (n = 27) and right-forelimb (n = 22) preference. The reaching performance was divided in 5 stages. The first two stages characterize the emotional condition of an animal, the following three were immediately related with the skilled movement. After preliminary testing, the head of the caudate nucleus contralateral to the preferred limb was electrolytically damaged. After surgery, rats were tested during 20 weeks, and in every test the following indices were measured: percent of rats which perform the movement characteristic for the given stage, stage duration, depth of reaching a flower seed from the tube, time necessary to obtain the best results etc. It was found that at the "emotional" stages, higher percent of the right-handed animals perform the characteristic movements, but they spend more time to complete these stages than the left-handed rats. In rats with the left-limb dominance the recovery of the specialized movement is positively correlated with the time of the recovery onset at all the stages, while there is no such correlation in rats with right-limb dominance. Both groups of animals reach the same depth of the tube in the course of recovery, but the left-handed rats attain these results later and gradually, while the right-handed animals attain the maximal extent of recovery spontaneously and earlier than left-handed ones.