Event-related synchronization and desynchronization of EEG during appraisal of threatening and pleasant visual stimuli in high anxious subjects

The 62-channel EEG was recorded while low (LA, n = 18) and high (HA, n = 18) trait-anxious subjects viewed sequentially presented neutral, threatening and pleasant IAPS stimuli. Event-related desynchronization (ERD) and synchronization (ERS) were studied in the delta, theta1, theta2, alpha1, alpha2, beta1, beta2, beta3, and gamma frequency bands. Between-group differences, related to stimulus emotionality, were linked to theta1 and theta2 bands. In the low theta at prefrontal sites in the test period of 100-700 ms after stimulus onset HA exhibited relative predominance of the left hemisphere in response to both threatening and pleasant stimuli, whereas LA yielded larger right than left hemisphere activity in response to all the three stimulus categories. In the upper theta band between group differences were associated with posterior cortical regions and the test period of 0-1000 ms after stimulus onset: HA exhibited the largest ERS to threatening, whereas LA prompted the largest ERS to pleasant stimuli. Finally, according to the ERD data, in the alpha1 band HA participants in comparison with LA revealed enhanced left hemisphere activation in response to all the stimulus categories. It is suggested that as it is indexed by theta-ERS relative predominance of the left hemisphere at prefrontal sites along with the largest bilateral activity of posterior cortical regions (i.e., enhanced higher order visual processing) to threatening stimuli could form the basis for general bias towards threatening information in HA at the very early stages of emotional processing.