Interhemispheric Transfer in Alexithymia: A Transcallosal Inhibition Study

Abstract

Objective: This study investigates the hypothesis that alexithymia is associated with an interhemispheric transfer deficit via the corpus callosum (CC). Method: The transcallosal inhibition paradigm was used to assess interhemispheric transfer. Transcranial magnetic stimulation (TMS) and peripheral electromyographic recordings were performed in 10 right-handed male and 10 female students with Toronto Alexithymia Scale (TAS-20) scores of ≧61 and controls (TAS-20 scores of <61). The transcallosal conduction time (TCT) reflects the TMS-induced inhibitory cortical activity that is mediated via the CC. Results: There was a significant interaction between gender and alexithymia (Wilks λ = 0.89; F = 3.4; d.f. = 2, 57; p = 0.04) indicating that alexithymic males had shorter bidirectional TCTs than controls and a significantly shorter left to right TCT than controls (p = 0.002). However, the left to right TCT was not significantly different from the right to left TCT in alexithymic males (p = 0.39). Alexithymic females were not different from controls. Conclusion: Our results clearly stand in contrast to the hypothesis of a transfer deficit due to a dysfunction of the CC in alexithymia. Facilitated, bidirectional transcallosal inhibition of the contralateral motor activity is associated with alexithymia in males. Facilitated cortical inhibition may be a neurobiological correlate of alexithymia.