Population coding of affect across stimuli, modalities and individuals

Area of Science:

• Neuroscience
• Psychology
• Sensory processing

Background:

• The brain's ability to integrate external sensory information with internal subjective experiences, such as affect, remains poorly understood.
• Understanding how the brain represents valence (pleasantness/unpleasantness) is crucial for deciphering subjective experience.

Purpose of the Study:

• To investigate the neural representation of affect by mapping population activity evoked by complex visual scenes and basic tastes.
• To determine if a common neural code exists for valence across different sensory modalities and abstract properties.

Main Methods:

• Used representational similarity analysis (RSA) to map neural population activity in humans.
• Presented participants with complex visual scenes and basic tastes while recording brain activity.
• Analyzed neural codes in ventral temporal cortex, anterior insular cortex, and orbitofrontal cortex (OFC).

Main Results:

• Identified a neural code representing a continuous axis of pleasant-to-unpleasant valence, distinct from physical or object properties.
• Found sensory-specific valence codes in the ventral temporal and anterior insular cortices.
• Discovered a sensory-independent valence code in the medial and lateral orbitofrontal cortices (OFC).
• The OFC's valence code was the only one capable of classifying experienced affect across participants.

Conclusions:

• The brain utilizes both sensory-specific and abstract neural codes to represent valence.
• The orbitofrontal cortex (OFC) plays a key role in representing subjective affect independent of sensory origin.
• This research provides a framework for objectively quantifying subjective affective experiences across stimuli, modalities, and individuals.