MULTIDAY RECORDINGS FROM OLFACTORY-BULB NEURONS IN AWAKE FREELY MOVING RATS - SPATIALLY AND TEMPORALLY ORGANIZED VARIABILITY IN ODORANT RESPONSE PROPERTIES

Chronic single-unit recordings were obtained from the mitral cell laye r of the olfactory bulbs of awake freely moving rats placed in an odor ant stream. Over periods up to five days, 618 recordings from 186 sing le neurons were obtained. Responses of individual neurons were found t o be quite variable over time, although this variability was below cha nce and was not incremental. The responses of nearby neurons were more similar than expected by chance but less similar than individual neur ons recorded at different times. However, responses of spatially well- separated neurons were more different than chance over short time peri ods. During rapid sniffing, single-unit responses became more variable , and the spatial organization of responses became less apparent. Thes e results suggest that neuronal responses in the olfactory bulb are ge nerally quite variable over time, with this variability increasing dur ing periods of rapid sniffing. These results are interpreted in the co ntext of a distributed, centrally modulated model of olfactory process ing.