[The alteration of a motor habit in rats with different motor preferences]

60 mixed-bred male white rats were trained to reach food in a horizontal tube with a forepaw. In the second test access to the tube was limited by a partition so that the left-handed rats were forced to use the right forepaw and the right-handed animals the left one. While the right-handed rats successfully changed for the unpreferred left limb the left-handed animals had problems in using the right forepaw. They were manifested in 1) longer time which it took for beginning manipulation with the unpreferred limb; 2) lower rate of manipulation; 3) smaller number of animals which succeeded in switching to the unpreferred limb; 4) higher number of attempts to use the preferred limb in the left-handed rats as compared with the right-handed ones. The authors suppose that distinctions in ability of rats to shift manipulatory reaction to the unpreferred forepaw result from different lability of inhibitory processes in the left and right hemispheres. In other words, ability of the right hemisphere to inhibit the program of manipulation with the dominant left paw (left-handed rats) is lower than that of the left hemisphere to inhibit the movement of the right forelimb (right-handed rats).