A Honeybee's Ability to Learn, Recognize, and Discriminate Odors Depends Upon Odor Sampling Time and Concentration

Animals sample sensory stimuli for longer periods when they must perform difficult discrimination tasks, implying that the brain's ability to represent stimuli improves as a function of time. Although it is true in other senses, few studies have examined whether increasing sampling time improves olfactory discrimination. In the experiments reported here, odor sampling time was controlled with the goal of testing whether odor concentration affected a honeybee's ability to learn, recognize, and discriminate odors. Increasing sampling time during conditioning and testing improved a honeybee's ability to learn, recognize, and differentiate low-concentration (0.0002 M) odors. For intermediate-concentration (0.02 M) odors, both acquisition and recognition improved when stimulus duration was longer, but discrimination was unaffected. Having longer to sample a high-concentration (2.0 M) stimulus also improved ability to recognize or differentiate odors. Differences in time to acquisition, but it did not affect the respond to the conditioned and novel odors during the test period depended on the difficulty of the discrimination task. The results suggest that the sensory coding of molecular identity takes longer for low-concentration odors.