Anticipation of affective images and event-related desynchronization (ERD) of alpha activity: an MEG study.

We investigated the event-related power decrease (event-related desynchronization: ERD) of the alpha bands associated with the anticipation of affective images. Participants (n=19) were presented with emotionally positive or negative images under different anticipatory conditions, and their brain responses were recorded using magnetoencephalography (MEG). In the Affective Cue conditions, the cue stimulus indicated the emotional valence (positive or negative) of the image. In the Null Cue condition, the cue stimulus did not include any information about the valence of the image, and in the No Cue condition, the affective image was presented without a preceding cue. The cues in the affective and null conditions were followed by emotional images. During the anticipation period for the affective image, the alpha ERD preceding an anticipated negative image was larger than that preceding an anticipated positive image; this effect had an occipital dominance. Furthermore, during the anticipation period, the lower-2-alpha ERD of the right frontal area showed the same result. These results demonstrate that anticipation of negative stimuli induced alpha ERD in both the visual and the right frontal cortex, indicating that top-down modulation may be provided by the right frontal cortex to the visual cortex.