Olfactory bulb responses telemetered during an odor discrimination task in rats.

Electrodes were chronically implanted in eight rats to record multiple-unit activity during the acquisition and performance of an isoamyl acetate (10(-3) concentration)/air discrimination task in order to obtain a water reward. Localized stimulus choice points permitted each rat to regulate its time of exposure to the two positive reinforcing stimuli. Each rat had stimulus sampling times of much less than 1 s while performing at an 80% or more correct choice level. Whereas four of the rats exhibited only occasional neural activity, probably due to electrode position, the other four developed individual neural burst patterns, after learning, which were different for the two stimuli. Changes in the neural patterns during testing, when they occurred in two of the four responsive animals, appeared to correlate with changes in stimulus sampling. These results confirm that much less than 1 s is needed for odor identification and demonstrate that multiunit activity can show differential response patterns. The results have possible implications for future studies.