Oscillatory EEG activity induced by conditioning stimuli during fear conditioning reflects Salience and Valence of these stimuli more than Expectancy

Imaging studies have described hemodynamic activity during fear conditioning protocols with stimulus trains in which a visual conditioned stimulus (CS+) is paired with an aversive unconditioned stimulus (US, painful laser pulse) while another visual stimulus is unpaired (CS−). We now test the hypothesis that CS Event-Related Spectral Perturbations (ERSPs) are related to ratings of CS Expectancy (likelihood of pairing with the US), Valence (unpleasantness) and Salience (ability to capture attention). ERSP windows in EEG were defined by both time after the CS and frequency, and showed increased oscillatory power (Event Related Synchronization, ERS) in the delta/theta Windows (0–8 Hz) and the gamma Window (30–55 Hz). Decreased oscillatory power (Event Related Desynchronization – ERD) was found in alpha (8–14 Hz) and beta Windows (14–30 Hz). The delta/theta ERS showed a differential effect of CS+ versus CS− at Prefrontal, Frontal and Midline Channels, while alpha and beta ERD were greater at Parietal and Occipital Channels early in the stimulus train. The gamma ERS Window increased from Habituation to Acquisition over a broad area from Frontal and occipital electrodes. The CS Valence and Salience were greater for CS+ than CS−, and were correlated with each other and with the ERD at overlapping Channels, particularly in the alpha Window. Expectancy and CS Skin Conductance Response were greater for CS+ than CS− and were correlated with ERSP at fewer Channels than Valence or Salience. These results suggest that alpha ERSP activity during fear conditioning reflects Valence and Salience of the CSs more than conditioning per se. The CS Valence and Salience were correlated with each other and with ERSP in the alpha Window more commonly than in other windows. Delta/theta ERSP differentiates between CS+ and CS− over a Midline Channel at which ERSP is correlated with Expectancy ratings. Although, both Expectancy and CS Skin Conductance Response (SCR) were correlated with ERSP this correlation occurred at fewer and different Channels than those for Valence or Salience. These results suggest that ERSP activity is related to Valence and Salience of the CSs more than to conditioning per se.