Dept of Psychology, University of North Carolina, Chapel Hill, NC  27514

Rodent OF and ABL are crucial to adaptive behavior based on the learned significance of environmental cues.  Multineuron recordings were made from each of these areas during an odor discrimination and reversal task using novel sets of odors paired with either sucrose or quinine.  Neural activity was examined in several event-related time windows for the influence of both odor identity and associative significance both pre and post-acquisition and after reversal.  Task-related and stimulus selective activity was found in each time window in each region, but specific characteristics differed between regions.  Selective activity in OF during odor sampling and a post-sampling interval preceding response was more frequently correlated with learned performance of the task, both during acquisition and after reversal, whereas selective activity in ABL during these time windows more frequently emerged prior to behavioral evidence of learning.  Selective activity in ABL reflecting behavioral acquisition appeared during the responding and reinforcement, particularly after sampling of negatively-reinforced odors.  Neurons in OF were similarly active during these time windows but exhibited a less pronounced bias than ABL for responding in conjunction with negatively-reinforced odors.  Acquisition of novel discriminations and subsequent reversal was also accompanied by changes in coincident and near-coincident firing in neuronal pairs, primarily in OF, suggesting the dynamic reorganization of neural ensembles there in response to changing task demands.  We propose complementary roles for OF and ABL in which information regarding the significance of cues encoded in circuits involving ABL is utilized transiently by networks in OF to guide olfactory behaviors. (supported by NIMH Grant R01 MH53667 and K05 MH01149)