Suspense and surprise: on the relationship between expectancies and P3

Area of Science:

• Cognitive Neuroscience
• Psychophysiology

Background:

• The P3 component of event-related potentials is a complex waveform with debated functional significance.
• Existing theories often overlook topographical distinctions within the P3, particularly between parietal and frontocentral regions.

Purpose of the Study:

• To test the hypothesis that the parietal P3 reflects stimulus anticipation (suspense) and the frontocentral P3 reflects unexpected events (surprise).
• To investigate the differential roles of parietal and frontocentral P3 components using a novel experimental paradigm.

Main Methods:

• A temporal anticipation paradigm was employed where participants responded to a target stimulus appearing within a clock face.
• Stimulus probability varied cyclically, creating predictable (12 o'clock) and unpredictable (other times) event contexts.
• Event-related potentials were recorded, focusing on the P3 component's frontocentral and parietal topographical distributions.

Main Results:

• A distinction between frontocentral and parietocentral P3 components was observed.
• The frontocentral P3 was significantly larger for unexpected (non-12 o'clock) stimuli.
• The parietal P3 was consistently large across all stimuli, not solely for unexpected events, partially supporting the suspense hypothesis.

Conclusions:

• The findings provide evidence for distinct neural generators of the P3, supporting differential roles in processing suspense and surprise.
• The results challenge the prevailing view that parietal P3 solely reflects unexpectedness, suggesting it may also index anticipatory processes.
• Variations in P3 topography across different experimental paradigms may arise from differing contributions of suspense and surprise components.