Relation of olfactory EEG to behavior: Factor analysis.

Rabbits were conditioned to lick (CR+) in response to one odor (CS+); another odor (CS-) served as a discriminative control (CR-). Electroencephalograms (EEGs) were recorded from arrays of 64 electrodes on the olfactory bulb in three stages, each with six sessions: in Stage I, odors A+ and B-; in Stage II, odors C+ and B-; and in Stage III, odors C+ and A-. Spatial EEG amplitude patterns were measured for multiple control (C), CS+, and CS- EEG bursts in each trial. Data were transformed via factor analysis and expressed by factor scores as spatial patterns specified by factor loadings. In discriminant analysis of the factor scores, we correctly classified the C and CS bursts on the average by 65-80% from all trials for each subject and session and by 75-90% for trials with correct CRs. The latter was confirmed with a stepwise linear discriminant analysis of the original 64-variable data. Factor patterns were relatively invariant within but changed between stages. The results implied that stable spatial patterns of bulbar activity emerged in respect to CSs under reinforcement and persisted until the stimulus-response contingencies were changed.