Performance of mice in an automated olfactometer: Odor detection, discrimination and odor memory

Mice were trained on a variety of odor detection and discrimination lash in 100- or 200-trial sessions using a go, no-go discrete trials operant condi tioning procedure. Odors, presented for 1 s on each trial, were generated b y an air dilution olfactometer (for threshold tests) and an easily construc ted eight-channel liquid dilution unit (for two- and multiple-odor discrimi nation tasks). Mice rapidly acquired the operant task and demonstrated exce llent stimulus control by odor vapors. Their absolute detection threshold f or ethyl acetate was similar to that obtained with rats using similar metho ds. They readily acquired four separate two-odor discrimination tasks and c ontinued to perform well when all eight odors were presented in random orde r in the same session and when reinforcement probability for correct respon ding was decreased from 1 to 0.5. Memory for these eight odors, assessed un der extinction after a 3t day rest period, was essentially perfect. Time sp ent sampling the odor on S+ and S- trials was highly correlated with respon se accuracy When accuracy was at chance levels (e.g. initial trials on a no vel task), stimulus sampling time on both S+ and S- trials was similar to 0 .5-0.7 s. As response accuracy increased, sampling time on S+ trials tended to increase and remain higher than sampling time on S- trials.