The human insula processes both modality-independent and pain-selective learning signals

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Pain Research

Background:

• Prediction errors (PEs) signal discrepancies between expected and actual events.
• The insula is crucial for pain processing and encodes unsigned PEs.
• It remains unclear if insula PE responses are pain-specific or general, and if it processes signed PEs.

Purpose of the Study:

• To investigate whether the insula processes unsigned prediction errors (PEs) in a modality-unspecific or specific manner.
• To determine if the insula can process signed PEs and whether these signals are modality-specific.
• To explore the role of insula PE processing in chronic pain conditions.

Main Methods:

• Functional magnetic resonance imaging (fMRI) and skin conductance response (SCR) were used.
• Participants (n=47) learned associations between conditioned stimuli (CS) and unconditioned stimuli (US; painful heat, loud sound).
• Both low and high intensity stimuli were employed for both modalities.

Main Results:

• Anterior insula activation correlated with unsigned intensity PEs across modalities, suggesting a general aversive surprise signal.
• Signed intensity PE signals were modality-specific.
• Signed PEs related to pain, but not sound, were localized to the dorsal posterior insula, an area involved in pain intensity processing.

Conclusions:

• The anterior insula exhibits unspecific aversive surprise signaling.
• The dorsal posterior insula shows modality-specific processing of signed PEs, particularly for pain.
• Aberrant insula PE processing may contribute to the chronification of pain.