Alexithymia shapes intersubject synchrony in brain activity during interoceptive sensation representations

Alexithymia is a subclinical condition that affects individuals' processing of emotions. Emerging evidence suggests that alexithymia results from a multidomain and multidimensional interoceptive failure. Although extensive research has examined the relationship between alexithymia and interoception, less is known about how alexithymia modulates the brain activity evoked by interoceptive sensations. In this study, we used task-based functional magnetic resonance imaging (fMRI) to assess intersubject correlations in response to interoceptive sensation words in individuals with high alexithymia and low alexithymia. Participants with high alexithymia (n = 29) and low alexithymia (n = 28) were instructed to view words during MRI scanning, each word corresponding to a specific emotional category related to interoceptive sensations. Intersubject correlation analysis identified several brain regions exhibiting increased synchronization in individuals with high alexithymia, including those involved in cognitive control. Follow-up analyses revealed that the left middle occipital gyrus and the right inferior frontal gyrus (orbital part) were more active during interoceptive sensation events in individuals with high alexithymia. Validation analyses revealed that the amygdala and insula are also crucial in representing interoceptive sensations. These findings shed light on the neural basis of interoceptive deficits in high alexithymia and have significant implications for the mechanisms regulating these differences.