Interhemispheric Transfer Deficit in Alexithymia: A Transcranial Magnetic Stimulation Study

Abstract

Background: 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. Methods: 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. Results: 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. Conclusions: 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.

Independent and Collaborative Contributions of the Cerebral Hemispheres to Emotional Processing

“…This could be due to the inverse relationship between size of the CC and severity of alexithymia (Habib et al, 2003). Lumley and Sielky (2000) observed similar findings of an association between alexithymia and poor inter-hemispheric transfer in normal participants, as did Romei et al (2008) and Parker et al (1999). Importantly, alexithymia does not seem to be due to hypoactivity of the RH, rather the RH shows significant activity for both positive and negative emotions (Aftanas and Varlamov, 2004, 2007).…”

Default Mode Network alterations in alexithymia: an EEG power spectra and connectivity study

“…According to a case-control design, we enrolled a control group consisting of eighteen subjects matched for sex and age (three men and fifteen women, mean age: 23.89 ± 4.85) with low alexithymia (TAS-20 total score ≤45, TAS− group). The cut-off values of TAS-20 used for selection of study groups were those adopted by Romei and coworkers25. Clinical and socio-demographic characteristics of the final sample are listed in Table 1.…”

Information-Based Approaches of Noninvasive Transcranial Brain Stimulation

“…This approach has been applied, for example, to test models of inter-hemispheric or inter-areal communication in specific populations (e.g. [62,63]) or functions (e.g. [64,65]).…”