The Sound of Feelings Figure 4. Correlations of Alexithymia Dimensions with P2 and P3 Amplitudes. Left: Negative correlation between the affective alexithymia dimension (fantasizing subscale) with P2 amplitudes in response to deviants in emotional prosody. Right: Negative correlation between the cognitive alexithymia dimension (verbalizing subscale) with P3 amplitudes in response to disgusted prosodic deviants. doi:10.1371/journal.pone.0036951.g004 amplitudes with increasing scores on emotionalizing was even more pronounced for deviants in emotional prosody spoken with high intensity than for those spoken with low intensity. For the fantasizing subscale, there was a three-way interaction fantasizing 6 intensity 6 region: F(2,112) = 6.414, p = .013]. Follow up tests on the factor region revealed a significant interaction fantasizing 6 intensity [F(1,56) = 6.455, p = .014] at central regions, suggesting a re- duction in central P3 amplitudes with increasing scores on fantasizing only for high intensity deviants in emotional prosody. Summary of ERP data. In summary, electrophysiological data for the detection of changes in emotional prosody suggested that alexithymia was significantly associated with alterations of early (N1, P2) as well as late (P3) ERP components. A dissociable impact of the two dimensions of alexithymia was observed: Only the cognitive dimension (analyzing subscale) was related to larger amplitudes of the early N1 component, while both the cognitive (analyzing subscale) and the affective dimensions (fantasizing subscale) were associated with reduced frontal P2 amplitudes. Both alexithymia dimensions were associated with reduced amplitudes of the late P3 component, but in a qualitatively different fashion: Individuals with difficulty verbalizing and identifying feelings (cognitive dimension) showed similarly reduced P3 amplitudes at parietal regions for all deviants in emotional prosody irrespective of the specific emotion and intensity, with the exception that individuals with difficulty verbalizing feelings exhibited a particu- larly diminished P3 response to disgusted prosody. In contrast to the cognitive dimension, the affective alexithymia dimension was sensitive to the difference in intensity with which the prosodic deviants were pronounced: High scores on emotionalizing (i.e., low emotional arousal) were associated with even stronger P3 amplitude reductions for prosodic deviants spoken with high intensity compared to those spoken with low intensity, while high scores on fantasizing (i.e. low abilities to fantasize, imagine etc.) were associated with reduced P3 amplitudes only for prosodic deviants spoken with high emotional intensity. Control analyses of all behavioral and electrophysiological data using the TAS-20 showed highly comparable results with the cognitive alexithymia dimension assessed with the BVAQ. Discussion The present study investigated the impact of the cognitive and affective alexithymia dimensions on the electrophysiological processing of attended and unattended emotional prosody. At unattended processing levels, the cognitive dimension was associated with a left-hemisphere bias during the early acoustic encoding of emotional speech, as reflected in overall shorter left- hemispheric eMMN latencies. No effect of the affective dimension was observed during the unattended processing of emotional speech. At attended processing levels, the cognitive alexithymia dimension modulated both early and late ERP components, reflected in larger N1 amplitudes and reduced P2 and P3 amplitudes. In contrast, the affective dimension did not modulate the early N1 component, but was also linked to reduced P2 amplitudes, and further showed a negative association with P3 amplitudes particularly for emotional prosody spoken with high emotional intensity. These results suggest that alexithymia modulates electrophysiological responses to emotional speech at attended as well as unattended processing levels, and provide evidence for a dissociable impact of the cognitive versus the affective alexithymia dimension on the processing of the emotional qualities of speech. Behavioral performance Behavioral data of the present study show that the mere detection of deviants in emotional prosody (task 2) was not affected by either alexithymia dimension. This is in line with the two previous studies on the relation between alexithymia and emotional prosody, which did not observe behavioral differences as a function of alexithymia during emotional prosody identifica- tion at the sentence level [15] and during cross-modal affective priming [44]. However, our findings indicate that when partici- pants are asked to specifically identify the emotion conveyed by brief vocal stimuli (task 3), deficits did become apparent, as evidenced by worse performance on disgusted prosody identifica- tion with increasing scores on both alexithymia dimensions. This could explain why behavioral differences were not observed in our previous study [44], as no disgusted but only happy and sad prosody were employed. Moreover, the current study asked subjects to identify the emotional prosody of brief vocal stimuli (600 ms), whereas the previous behavioral study on emotional PLoS ONE | www.plosone.org 10 May 2012 | Volume 7 | Issue 5 | e36951