Subclinical alexithymia modulates early audio-visual perceptive and attentional event-related potentials

Previous studies have highlighted the advantage of using audio-visual oddball tasks (instead of unimodal ones) in order to electrophysiologically index subclinical behavioral differences. Since alexithymia is highly prevalent in the general population, we investigated whether the use of various bimodal tasks could elicit emotional effects in low- vs. high-alexithymic scorers.

Fifty students (33 females and 17 males) were split into groups based on low and high scores on the Toronto Alexithymia Scale (TAS-20). During event-related potential (ERP) recordings, they were exposed to three kinds of audio-visual oddball tasks: neutral-AVN-(geometrical forms and bips), animal-AVA-(dog and cock with their respective shouts), or emotional-AVE-(faces and voices) stimuli. In each condition, participants were asked to quickly detect deviant events occurring amongst a train of repeated and frequent matching stimuli (e.g., push a button when a sad face-voice pair appeared amongst a train of neutral face-voice pairs). P100, N100, and P300 components were analyzed: P100 refers to visual perceptive and attentional processing, N100 to auditory ones, and the P300 relates to response-related stages, involving memory processes.

High-alexithymic scorers presented a particular pattern of results when processing the emotional stimulations, reflected in early ERP components by increased P100 and N100 amplitudes in the emotional oddball tasks [P100: F (2, 48) = 20,319, p < 0.001; N100: F (2, 96) = 8,807, p = 0.001] as compared to the animal or neutral ones. Indeed, regarding the P100, subjects exhibited a higher amplitude in the AVE condition (8.717 μV), which was significantly different from that observed during the AVN condition (4.382 μV, p < 0.001). For the N100, the highest amplitude was found in the AVE condition (-4.035 μV) and the lowest was observed in the AVN condition (-2.687 μV, p = 0.003). However, no effect was found on the later P300 component.

Our findings suggest that high-alexithymic scorers require heightened early attentional resources in comparison to low scorers, particularly when confronted with emotional bimodal stimuli.