A beta oscillation network in the rat olfactory system during a 2-alternative

26 27 We previously showed that in a 2-alternative choice (2AC) task, olfactory bulb (OB) 28 gamma oscillations (~70 Hz in rats) were enhanced during discrimination of structurally 29 similar odorants (fine discrimination) vs. discrimination of dissimilar odorants (coarse 30 discrimination). In other studies (mostly employing go/no-go tasks) in multiple labs, beta 31 oscillations (15-35 Hz) dominate the LFP signal in olfactory areas during odor sampling. 32 Here we analyzed the beta frequency band power and pairwise coherence in the 2AC 33 task. We show that in a task dominated by gamma in the OB, beta oscillations are also 34 present in three interconnected olfactory areas (OB and anterior and posterior pyriform 35 cortex). Only the beta band showed consistently elevated coherence during odor sniffing 36 across all odor pairs, classes (alcohols and ketones) and discrimination types (fine and 37 coarse), with stronger effects in first than in final criterion sessions (> 70% correct). In 38 the first sessions for fine discrimination odor pairs, beta power for incorrect trials was the 39 same as that for correct trials for the other odor in the pair. This pattern was not repeated 40 in coarse discrimination, in which beta power was elevated for correct relative to 41 incorrect trials. This difference between fine and coarse odor discriminations may relate 42 to different behavioral strategies for learning to differentiate similar vs. dissimilar odors. 43 Phase analysis showed that the OB led both pyriform areas in the beta frequency band 44 during odor sniffing. We conclude that the beta band may be the means by which 45 information is transmitted from the OB to higher order areas, even though task specifics 46 modify dominance of one frequency band over another within the OB. 47