Separating Measures of Learning and Incentive in Water Maze Experiments with Aging Inbred Strains of Mice

Abstract

Three age groups of DBA/2J and C57BL/6J mice (5, 10, and 16 mo.) were given reversal learning trials in a spatial water maze with water temperatures (incentive conditions) of 12, 22, 34, and 45°C. Swimming times to the choice point were used as the index of motivation while trials-to-criterion were used as a measure of learning. Age effects were nonsignificant. For both strains water temperatures of 12°C and 45°C resulted in increased swimming times relative to 34°C and 22°C, although the effect of incentive of water temperature was less pronounced in the DBA/2J strain. Increased swimming time (motivation) was not accompanied by a corresponding decrease in trials-to-criterion (learning). Data indicate the importance in water-maze experiments of separating measures of incentive and learning by the mouse for which effects of incentives on learning are of concern.