Separating Subjective from Objective Food Value in the Human Insula: An Exploratory Study Using Intracranial EEG

Area of Science:

• Neuroscience
• Gastroenterology
• Psychology

Background:

• The human insula integrates internal states with external food cues, but its precise role is limited by neuroimaging temporal resolution.
• Intracranial EEG (iEEG) offers a unique opportunity to explore the insula's temporal dynamics in food cue processing.

Purpose of the Study:

• To investigate how the insula encodes subjective and objective properties of food stimuli.
• To determine how hunger and satiety modulate insular cortex activity in response to food cues.

Main Methods:

• Eight patients with drug-resistant epilepsy undergoing pre-surgical evaluation.
• Recorded intracranial EEG (iEEG) event-related potentials (ERPs) in the insular cortex.
• Collected subjective ratings and objective nutritional values of visual food cues in hungry and satiated states.

Main Results:

• Hunger amplified later ERPs (350-450 ms), while satiety enhanced early responses (150-250 ms).
• Neural activity for nutritional values was largely uncorrelated with subjective ratings, suggesting distinct processing streams.
• Mid- and posterior insula showed greater sensitivity to both subjective and nutritional information compared to the anterior insula.

Conclusions:

• The insula differentiates implicit and explicit food signals based on homeostatic state.
• Findings support a dual-route model for food cue processing.
• Results may inform interventions for disordered eating by targeting insular activity.