Performance of Mice in an Automated Olfactometer: Odor Detection, Discrimination and Odor Memory

Abstract

Mice were trained on a variety of odor detection and discrimination tasks in 100- or 200-trial sessions using a go, no-go discrete trials operant conditioning procedure. Odors, presented for 1 s on each trial, were generated by an air dilution olfactometer (for threshold tests) and an easily constructed eight-channel liquid dilution unit (for two- and multiple-odor discrimination tasks). Mice rapidly acquired the operant task and demonstrated excellent stimulus control by odor vapors. Their absolute detection threshold for ethyl acetate was similar to that obtained with rats using similar methods. They readily acquired four separate two-odor discrimination tasks and continued to perform well when all eight odors were presented in random order in the same session and when reinforcement probability for correct responding was decreased from 1 to 0.5. Memory for these eight odors, assessed under extinction after a 32 day rest period, was essentially perfect. Time spent sampling the odor on S+ and S- trials was highly correlated with response accuracy. When accuracy was at chance levels (e.g. initial trials on a novel task), stimulus sampling time on both S+ and S- trials was approximately 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.

Ca2+-activated Cl− currents are dispensable for olfaction

“…Using an automated olfactometer 17,30,38,39 , we tested the mice using an associative olfactory learning task. The mice were trained to sample two different stimuli, one of which was associated with a water reward, and to lick only in response to the rewarded odor.…”

Enhanced urinary odor discrimination in female aromatase knockout (ArKO) mice

“…A flow-chart outlining the operant task is shown in Fig. 1, and the olfactometer has been previously described by Bodyak and Slotnick (1999). The percent of correct responses was determined for each block of 20 trials (a total of 5 blocks were given during each daily test session).…”

“…Notably, the odor concentration which the animal was presented within the sampling port was much lower than the volume/volume (v/v) concentration which was placed in the odor vials. This decrease in concentration is due to several factors (e.g., air flow rate, surface area of liquid odor in flask) and results in approximately 3% of the odor's v/v concentration actually passing the nose of the animal as it samples in the port (Bodyak and Slotnick, 1999). For example, an odor flask holding a 10 −3…”

“…The concentrations of the social odors and non-social odors that we chose for the discrimination paradigms are based on pilot work showing that animals could readily acquire and complete a task detecting urine at a 10 −2 concentration and amyl acetate and butyl acetate at a 10 −3 concentration. Similar concentrations of acetates have been used in past olfactometric work on mice (Bodyak and Slotnick, 1999).…”

A test to identify judgement bias in mice

“…All testing was performed with odours as conditioned stimuli, considering the ability of mice to discriminate even slight differences between odours [40]; this ability is also found in individuals of the BALB/c and the 129S1/SvImj sub-strain [41]. Odour mixtures have been used before in a judgement bias experiment with honeybees [17].…”