Abstract
Our monkeys learned to pick up forceps for food-taking: when food was in left and forceps in right of them with its tip facing food ( 3 o.clock), monkeys reached for and grasped forceps using right hand and brought it to and picked up food. We showed that they can invent strategies to use forceps. Here, we studied further in two monkeys what they had learned from the 3 o.clock task and how they learn new motor tasks when the learned task is modified. First, we presented forceps with the tip directed opposite (9 o.clock) from original. At the first trial on the 9 o.clock task, both did not take action at the beginning, and when prompted, one monkey refused and the other reluctantly reached (i.e. taking a longer time before reaching) and grasped forceps backward. The latter refused to act after ca 20 trials. Second, the direction of forceps was changed by a step of 30 deg from 3 to 9 o.clock. In 4-5 days, they became to grasp forceps correctly on 9 o.clock task by taking two motor steps: they first reoriented forceps and then grasped it in order. The strategies may have emerged during practice: e.g. they sometimes changed the grip when they grasped forceps too short or too long, or when he grasped it reversely, they shifted forceps to the left hand and then return it to the right hand to correct the direction. We suggest that initially they soon understood that the 9 o.clock task was a novel one for which they had no motor program, and that they solved the new tasks by recalling appropriate motor memories stored through active practice in the past. [J Physiol Sci. 2007;57 Suppl:S157]
