| This study investigated whether deficits in emotional awareness is associated predominantly with a compromise in right hemisphere function or in interhemispheric communication, whether attentional or only semantic processes are affected, and whether the deficit is emotion-specific. Subjects decided whether a face presented to the left (LVF) or right (RVF) visual field matched the face presented in the previous trial, using either facial expression (happy, sad) or poser identity (10 actors) to judge the match. In response to LVF/right-hemisphere (RH) presentation, alexithymics were predicted to show reduced Event-Related Potential (ERP) components in the expression task but not in the identity task, a control condition not requiring processing of emotional features. An interhemispheric deficit would be shown by reduced ERP components when the stimuli appeared in opposite visual fields and interhemispheric communication was required. Participants scored in the bottom (Low Alexithymics, n = 24) or top (High Alexithymics, n = 35) 20% on the 20-item Toronto Alexithymia Scale.; Right hemisphere dysfunction as well as an interhemispheric deficit were indicated by the behavior of early attentional (P100) and later semantic (N400, P300) components in the High Alexithymic (HA) group. Many of these effects were emotion-specific, but some were not. A P100 selective attention deficit indicating reduced right hemisphere (RH) involvement in individuals scoring high in alexithymia was correlated with a failure to differentiate emotional valence when interhemispheric communication was required. Gender moderated several effects. Most notably, only female HAs exhibited: (1) an N170 that was larger over the posterior RH than left hemisphere (LH), suggesting higher autonomic arousal, and (2) a lack of differentiation by N400 of facial expressions over the posterior RH when interhemispheric communication was required. These effects were not correlated, indicating they occurred in different HA females. This may be explained by the existence in the sample of mild subtypes resembling both Type I (absence of experience of emotion, related to a right hemisphere deficit) and Type II (experience intact with cognitions about emotion absent, related to an interhemispheric deficit) alexithymics, as distinguished by Bermond (1995). Well-validated measures for distinguishing between these subtypes are not currently available. |
