Rapid and automatic discrimination between facial expressions in the human brain

Area of Science:

• Neuroscience
• Cognitive Science
• Psychology

Background:

• Previous studies used fast periodic visual stimulation (FPVS) and EEG to detect automatic responses to facial expression changes.
• The brain's ability to rapidly categorize basic facial expressions is crucial for social interaction.

Purpose of the Study:

• To isolate and characterize specific neural signatures for the rapid categorization of five basic facial expressions (anger, disgust, happiness, fear, sadness) and neutral faces.
• To investigate if distinct neural substrates underlie the processing of different facial expressions.

Main Methods:

• Scalp electroencephalography (EEG) was recorded from 15 participants.
• Stimuli consisted of rapidly alternating images (6 Hz) of faces displaying one of five basic emotions or a neutral expression.
• Expression-specific brain responses were analyzed using frequency-domain analysis at 1.2 Hz and its harmonics.

Main Results:

• Robust, individual-specific, and objective neural signatures were identified over occipito-temporal sites for each emotion and neutral expression.
• Neural responses to different expressions (anger, disgust, happiness, sadness) varied qualitatively.
• Neutral faces elicited a significantly larger specific neural signature compared to expressive faces.
• Fear processing showed a strong, contrasted response with other expressions, linked to a specific signature over ventral occipito-temporal sites.

Conclusions:

• Specific EEG signatures for distinct facial expressions can be isolated, suggesting partially different neural substrates.
• The human brain exhibits a strong and highly selective system-level neural response to fear, consistent with its survival importance.