Neural substrates of interoceptive sensibility: An integrated study in normal and pathological functioning.

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Neuroimaging

Background:

• Interoception, the sense of the body's internal state, has evolved from focusing solely on visceral sensations to encompassing broader somatosensory feelings.
• Understanding the neural basis of interoception requires differentiating between these visceral and somatosensory components.

Purpose of the Study:

• To investigate the distinct neural underpinnings of interoceptive sensibility for visceral and somatosensory feelings.
• To correlate structural brain measures (morphometry and connectivity) with self-reported interoceptive awareness.

Main Methods:

• Structural MRI (T1w, DTI) and voxel-wise analyses (GI, FA) in healthy individuals.
• Voxel-Based Lesion-Symptom Mapping (VLSM) and track-wise hodological lesion-deficit analysis (TWH) in brain-damaged patients.
• Self-Awareness Questionnaire (SAQ) to assess visceral (F1) and somatosensory (F2) interoceptive sensibility.

Main Results:

• Somatosensory sensibility (F2) correlated positively with fractional anisotropy (FA) in multiple white matter tracts, including the corticospinal tract and cingulum.
• Visceral sensibility (F1) showed a positive association with gyrification index (GI) in the anterior cingulate cortex and relied on the right posterior insula.
• Lesion analysis confirmed that F1 is associated with the right posterior insula, while F2 is linked to subcortical structures and associated white matter.

Conclusions:

• The findings support a clear dissociation in the neural substrates of visceral and somatosensory interoceptive sensibility.
• Different brain structures and white matter pathways underpin the awareness of internal bodily states versus external somatosensory feelings.