Alexithymia and the split brain: VI. Electroencephalographic correlates of alexithymia

Electroencephalographic recordings of eight corpus callosotomy patients and eight precision-matched control subjects were obtained as subjects watched a film symbolically depicting death. A content-analytic measure of alexithymia was regressed on eight auto-spectral alpha-band intensity averages and on subsets of alpha-band coherence averages. Results were interpreted on the basis of three possible mechanisms of alexithymia: (1) Alexithymic subjects had more right-temporal alpha-band intensity, suggesting inadequate understanding of the film. (2) A possible lack of inner speech in alexithymics was suggested by their relative alpha abundance of the left frontal and left temporal channels but left parietal alpha desynchronization, and by their lower left frontotemporal but higher left parietofrontal and left parietotemporal coherences. (3) Alexithymic subjects had higher right frontal-left parietal and left frontal-left parietal coherences, suggesting possible interhemispheric inhibition of expression. Expressive subjects had higher right frontal-left temporal (and homologous interhemispheric frontal, parietal, and frontal) coherences, suggesting interhemispheric facilitation of verbal expression.