Interhemispheric transfer deficit in alexithymia: a transcranial magnetic stimulation study.
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.
Romei
Vincenzo
V
Department of Psychology, University of Rome La Sapienza, Rome, Italy. Vincenzo.Romei@medecine.unige.ch
De Gennaro
Luigi
L
Fratello
Fabiana
F
Curcio
Giuseppe
G
Ferrara
Michele
M
Pascual-Leone
Alvaro
A
Bertini
Mario
M
D000328:Adult; D000342:Affective Symptoms / Q000175:diagnosis / Q000503:physiopathology*; D003337:Corpus Callosum / Q000503:physiopathology; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000503:physiopathology*; D009415:Nerve Net / Q000503:physiopathology*; D009433:Neural Inhibition / Q000502:physiology; D012720:Severity of Illness Index; D050781:Transcranial Magnetic Stimulation / Q000379:methods*