Transcallosal inhibition in patients with and without alexithymia.

Objective: Previous results indicated a facilitated transcallosal inhibition via the corpus callosum (CC) in alexithymic male students. This study investigates transcallosal inhibition in alexithymic and nonalexithymic psychiatric inpatients.

Method: Transcallosal inhibition was elicited by means of transcranial magnetic stimulation (TMS) of the primary motor cortex. Seven right-handed male and 12 female psychiatric patients with Toronto Alexithymia Scale (TAS-20) scores of > or = 61 and 12 patients with TAS-20 scores of < 51 were investigated. The transcallosal conduction time (TCT) reflects the TMS-induced inhibitory cortical activity that is mediated via the CC.

Results: There was a significant effect of alexithymia on TCT (Wilks lambda = 0.76; F = 4.1; d.f. = 2, 26; p = 0.027) indicating that alexithymic patients had shorter bidirectional TCTs than nonalexithymic patients. The in-between models showed a significant impact of alexithymia on both right to left TCT (F = 4.8; d.f. = 1; p = 0.038) and left to right TCT (F = 5.0; d.f. = 1; p = 0.033). Neither gender nor scores of depression (Montgomery-Asberg Depression Rating Scale) had any significant effects on TCT.

Conclusion: Our results confirm and extend the previous findings of a facilitated, bidirectional transcallosal inhibition in alexithymia to male and female psychiatric inpatients. Facilitated transcallosal inhibition should be considered as a neurobiological correlate of alexithymia.