Visual event-related potentials in subjects with alexithymia: modified processing of emotional aversive information?

A modified autonomous response (e.g., electrodermal activity) in subjects with alexithymia (a reduced ability to identify and communicate emotions) while processing emotional information is well known. However, the functional and neurobiological bases of this impairment are unclear. Do subjects with alexithymia suffer from a primary lack of perception ("emotional blindness"), or is alexithymia based on incomplete information processing due to immature undifferentiated cognitive schemes? The study investigates if subjects with alexithymia show a modified central response as a correlate of classifying emotional aversive stimuli.

Twenty subjects with high alexithymia and 20 with low alexithymia (selected by the 20-item Toronto Alexithymia Scale) were investigated within a modified odd-ball paradigm. Three different stimulus categories were presented: aversive (probes) and affective neutral pictures (nontargets and instructed targets). Visual event-related EEG potentials and subjective data were recorded.

All subjects showed elevated positive amplitudes or mean activity after probe presentation in the latency range: 150-260, 280-450, and 600-1500 msec. Subjects with alexithymia displayed increased positive components (especially P2) of visual event-related potentials after probe presentation than subjects without alexithymia. Subjects without alexithymia more frequently verbalized the emotional impact of these aversive pictures than subjects with alexithymia.

These findings do not support the assumption of a primary lack of perception in alexithymia. Subjects with alexithymia show central correlates of perception and classification of aversive pictures. They may need more effort and cognitive recourses to process emotional information. Nevertheless, spontaneous verbal reference to emotional stimulus aspects is reduced.