Motor skill recovery in rats with various forelimb preference subjected to lesions in the caudate nucleus

Rats were trained for retrieving a sunflower seed from a tube using a forelimb. In the process of training, all the animals were divided in two groups: with the right- and left-limb preference. The period of learning was divided in two emotional (after the period of anxiety the animal takes a sunflower seed from the flow of a chamber) and three motor stages (different degrees of dexterity and precision in reaching a seed in the tube and grasping it). After a rat learned the skilled movement, the caudate nucleus was lesioned contralaterally to the preferred limb. After surgery, the animals were tested for recovery of the motor skill. The stages of recovery were the same as during learning. "Right-" and "left-handed" rats were compared in the percentage of animals performing each stage, duration of each stage, the depth of the tube reached by the animal's forelimb, and time required for obtaining the best results. The "right-handed" rats dominated in the percentage of animals performing the emotional stages and later began to recover the skilled movement (the crucial motor stage) but faster acquired their individual maximal depth of reaching a seed in the tube than the "left-handed" animals. The recovery of the skilled movement in the "left-handed" animals was a more gradual process than that in the "right-handed" ones.