A quantitative genetic analysis of runway learning in mice

Summary Individual differences in the acquisition and extinction of a straight runway response were studied. Sixty-four pairs of mice chosen from a heterogeneous population and motivated by hunger were given 5 massed trials a day in the runway for 5 days of acquisition and 3 days of extinction. They were then mated at random and their offspring were tested using the same procedures. A second degree polynomial function (Y = a - bX - + -²) was fitted to the learning curve of each individual. Since learning may be defined as change in behavior, a, b and c may be regarded as overall activity, amount of learning and rate of learning respectively. Estimates of the heritability were made by regressing the means of the offspring on the parent means. Heritability estimates of the 3 parameters of the learning curve (the mean, b and c) were respectively 0.41±0.12, 0.30±0.10, and 0.26±0.14 for running times and 0.36±0.11, 0.19±0.12, and 0.25±0.10 for starting times. The correlations between traits were also partitioned into their genetic and environmental components. This analysis suggested that many of the same genes were contributing to individual differences in the comparable components for running and starting times for acquisition and extinction.From a thesis submitted by the senior author in partial fulfillment of the requirements for the Ph.D. degree at the University of Colorado. This research was supported by research grant GM-14547 from the National Institute of General Medical Sciences.