ScienceDaily (May 27, 2008) — Italian investigators have published a new study on the neurobiologic correlates of the inability to express emotions (alexithymia) in the third 2008 issue of Psychotherapy and Psychosomatics.

A deficit in interhemispheric transfer was hypothesized in alexithymia more than 30 years ago, following the observation that split-brain patients manifest certain alexithymic characteristics. However, direct evidence of interhemispheric transfer deficit has never been provided. This study investigated the hypothesis of a transcallosal interhemispheric transfer deficit in alexithymia by means of paired-pulse transcranial magnetic stimulation.

A random sample of 300 students was screened for alexithymia using the Italian version of the 20-item Toronto Alexithymia Scale. Eight right-handed males and eight females with high alexithymic scores and an age- and gender-matched group with low alexithymic scores were selected. A first (conditioning) magnetic stimulus was delivered to one motor cortex followed by a second (test) stimulus to the opposite hemisphere at different interstimulus intervals for both motor cortices. Motor evoked responses were recorded from the abductor digit minimi muscles.

At the end of the investigation, high alexithymic subjects showed reduced transcallosal inhibition as compared to low alexithymic subjects at interstimulus intervals of 10, 12 and 14 ms in the left-to-right and right-to-left interhemispheric transfer directions.

Results point to functional differences in transcallosal interactions in high alexithymic as compared to low alexithymic subjects, supporting the hypothesis of an interhemispheric transfer deficit in alexithymia.

Romei,V; De Gennaro,L.; Fratello, F.; Curcio, G.; Ferrara, M.; Pascual-Leone, A.; Bertini, M.: Interhemispheric Transfer Deficit in Alexithymia: A Transcranial Magnetic Stimulation Study. Psychother Psychosom 2008;77:175-181

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