Event-related delta and theta synchronization during explicit and implicit emotion processing

Area of Science:

• Neuroscience
• Cognitive Psychology

Background:

• Emotion information processing can occur via distinct online and offline modes.
• These modes differ in processing speed, analytical depth, and conscious awareness.
• Event-related electroencephalogram (EEG) theta and delta synchronization serve as neural markers for emotion processing.

Purpose of the Study:

• To investigate the neural correlates of emotion processing in explicit and implicit modes using EEG.
• To differentiate the temporal dynamics and brain regions involved in conscious and unconscious emotion perception.

Main Methods:

• Two experiments were conducted, varying the task demands (explicit emotion evaluation vs. implicit gender discrimination).
• EEG data was recorded, focusing on theta and delta synchronization patterns.
• Source localization analysis was employed to identify brain regions associated with specific processing modes.

Main Results:

• Both emotional and neutral stimuli elicited stronger theta and delta synchronization compared to baseline.
• Synchronization was more pronounced in individuals with higher emotional sensitivity.
• Implicit emotion processing showed enhanced early synchronization (before 250 ms), particularly in the right parietal cortex and insula for angry and happy faces, respectively.
• Explicit emotion processing demonstrated enhanced late synchronization (after 250 ms) in the left temporal lobe and bilateral prefrontal cortex for angry and happy faces, respectively.

Conclusions:

• Distinct neural signatures exist for implicit (early, right-lateralized) and explicit (late, more widespread) emotion processing.
• Theta and delta synchronization are reliable markers for differentiating conscious and unconscious emotion perception.
• The findings contribute to understanding the neural basis of subjective emotional experience and awareness.