Offline, EEG signals were re-referenced to linked ear lobes, baseline corrected (0–1000 ms before stimulus onset), and high pass filtered (0.2 Hz, 24 dB/ octave). The data were then corrected for eye movements [30]. In addition, trials contaminated by any further artifacts (amplitudes between −50 and +50 µV) within the first 1400 ms after odor presentation were eliminated from the analysis. Subsequently, a zero phase shift digital low pass filter (Butterworth-filter, 7 Hz, 24 dB/ octave) was applied. The 60 scalp electrode positions were subdivided into nine areas, and a mean peak for each of these regions was calculated by averaging adjacent electrodes in anterior, central, and posterior areas for the left and right hemisphere as well as for midline electrodes [sagittal line: anterior (A), central (C), posterior (P); transversal line: left (L), midline (M), right (R); sagittal by transversal: AL: Fp1, AF7, AF3, F7, F5, F3; AM: Fpz, F1, Fz, F2; AR: Fp2, AF4, AF8, F4, F6, F8; CL: FT7, FC5, FC3, T7, C5, C3, TP7, CP5, CP3; CM:FC1, FC2, C1, Cz, C2, CP1, CPz, CP2; CR: FC4, FC6,
