Digital measurement of operant disk press force maintained in CD-1, BALB/c, and C57BL/6 mice.

Force of disk press responses by inbred (C57BL/6 and BALB/c) and outbred (CD-1) mice were measured with a PC/DOS-based system, which allowed for continuous measurement of pressing, as well as for control of reinforcer presentation on the basis of response-force dimensions. Photobeam-based measurement of mouse entry into a hopper where reinforcers were presented provided additional information about anticipatory and consumatory behavior in relation to environmental stimuli leading up to reinforcer delivery. Disk pressing was generated and measured with the use of an analog-to-digital interface with all three mouse strains. The strains differed in the physical and temporal characteristics of the disk press, as well as in the behavioral chain leading to reinforcer presentation. These measurement methods appear well suited for quantitating functional behavioral differences occasioned by genetic variations in mice.