Effects of Closed Mouth vs. Exposed Teeth on Facial Expression Processing: An ERP Study

Area of Science:

• Neuroscience
• Cognitive Psychology
• Visual Perception

Background:

• Facial recognition involves complex neural processing.
• Emotional expressions and specific facial features, like mouth display, can influence perception.
• Event-related potentials (ERPs) are crucial for understanding the timing and neural basis of these processes.

Purpose of the Study:

• To investigate how emotional expression and mouth display modulate event-related potential (ERP) waveforms during facial recognition.
• To determine the specific effects of open vs. closed mouths and emotional valence on neural responses.
• To clarify the role of mouth display in face perception research.

Main Methods:

• 42 participants performed gender categorization tasks with full and cropped face images.
• Stimuli included faces varying in gender, race/ethnicity, emotional expression (fearful, happy, neutral), and mouth display (open with teeth, closed).
• Event-related potentials (ERPs), specifically N170 and P100 amplitudes and latencies, were analyzed using statistical tests and Monte Carlo simulations.

Main Results:

• N170 amplitude was significantly larger for open-mouth displays, irrespective of emotion.
• P100 amplitude showed a significant interaction between emotional expression and mouth display.
• Fearful faces elicited faster N170 responses compared to happy and neutral faces (p < 0.01).

Conclusions:

• Mouth display is a critical factor that must be controlled in studies of emotional face processing.
• While N170 may not be directly modulated by emotional expression, emotional intensity could be a confounding factor.
• The brain processes fearful expressions more rapidly than neutral or happy ones, offering insights into neural dynamics of emotion perception.