Interhemispheric transfer deficit and alexithymia.

The hypothesis that alexithymia reflects a functional disconnection between the two cerebral hemispheres was examined in 25 male combat veterans with posttraumatic stress disorder (PTSD). Multiple regression analysis revealed that the efficiency of interhemispheric communication, evaluated with a tactile finger localization task, was a significant predictor of the degree of alexithymia, as measured by the Toronto Alexithymia Scale, independent of PTSD severity and IQ. The PTSD subjects without alexithymia did not differ on the finger localization task from 10 male control subjects without alexithymia. These data suggest that at least some forms of alexithymia may be mediated by an interhemispheric communication deficit.

Interhemispheric transfer in major psychoses.

The authors studied 25 schizophrenics and 21 affectively ill, pure right-handed, male patients by using the Tactual Performance Test (TPT), a stereognosis block identification task, and an anomia task to evaluate their interhemispheric information transfer. Although both groups generally had difficulty performing the TPT, the pattern of performance deficit was not different between diagnostic groups and was not consistent with a clear-cut interhemispheric transfer problem. Schizophrenics made more naming errors and TPT preferred-hand errors than did affectively ill patients, whereas affectively ill patients were able to identify more blocks with their preferred hand than could the schizophrenics. Patient index age, illness onset age, handedness, medications received at time of testing, personal and family history of alcoholism, and family history of major mental illness did not relate to cognitive performance. It is concluded that these data are not consistent with an interhemisphere transfer deficit that is specific for schizophrenia, but they are consistent with either a nonspecific interhemisphere transfer deficit in psychoses or with a left or bilateral hemisphere impairment in schizophrenia.