Alexithymia and regional gray matter alterations in schizophrenia

Alexithymia is characterized by deficits in emotional self-awareness. Although alexithymia refers to a deficit in recognizing one's own emotions, some studies have focused on the relation between alexithymia and impaired social cognition. An association between alexithymia and schizophrenia has been previously reported, but the brain structures involved remain unclear. The present study investigated associations between alexithymia and specific brain structures to determine whether these regions overlapped with key structures underlying social cognition. Twenty-one patients with schizophrenia and 24 age-, gender- and education level-matched healthy controls underwent structural magnetic resonance imaging. Alexithymia was assessed using the 20-item Toronto Alexithymia Scale (TAS-20). We applied voxel-based morphometry to investigate the correlation between TAS-20 scores and regional brain alterations. TAS-20 scores were significantly higher in patients than controls. Bilateral ventral striatum and left ventral premotor cortex volumes were negatively correlated with TAS-20 total scores in controls, while left supramarginal gyrus (SMG) volume was negatively correlated with TAS-20 total scores in patients. These results suggest that schizophrenia is associated with alexithymia, and that gray matter alterations of the left SMG constitute a key pathology underlying alexithymia in schizophrenia. This association may be related to deficits in self-other distinction, self-disturbance, and language processing in schizophrenia.