Brief report
Alexithymia in healthy young men: A voxel-based morphometric study

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Abstract

Background

Alexithymia is a personality construct predominately associated with an impaired ability to identify and communicate emotions. Functional imaging studies showed that an altered function of the anterior cingulate cortex (ACC) may be relevant in alexithymia. In this study we investigated if the altered functional anatomy is related to structural changes (A) in the whole brain and (B) specifically in the ACC by applying a region-of-interest analysis.

Methods

33 high- and 31 low-alexithymic right-handed young male subjects (selected by the 20-item Toronto Alexithymia Scale, TAS-20) were investigated using voxel-based morphometry (VBM) on high-resolution 3D magnetic resonance images. The group differences were analyzed by applying voxel-wise comparisons using two-sample t-tests. Moreover regression analyses with regard to the individual TAS-20 sum scores were calculated.

Results

Neither the subtraction analyses nor the correlation analyses revealed significant differences between high- and low-alexithymic subjects. Thus, according to our results, the null hypothesis of no structural difference between the groups could not be rejected.

Limitations

The findings cannot be generalized to female subjects.

Conclusions

Our results did not reveal morphological differences between high- and low-alexithymic subjects. The functional differences known from imaging studies could not be attributed to underlying anatomical changes. Thus, the personality trait of alexithymia might be associated with fewer morphological abnormalities than previously assumed.

Introduction

Alexithymia is a personality construct characterized by difficulties in identifying and describing subjective feelings or emotional aspects of social interaction, difficulties to distinguish between feelings and bodily sensations, and an externally oriented thinking style focusing on facts without affective involvement (Bagby et al., 1994b, Franz et al., 2004, Taylor, 2000). A pronounced inability (high alexithymia) does not represent a psychological disorder in itself. However, a high degree of alexithymia is associated with an enhanced risk of psychological impairment including chronic pain, somatoform disorders, addictive disorders, anxiety and depression (Dorard et al., 2008, Honkalampi et al., 2000, Larsen et al., 2003, Taylor, 2000, Taylor and Bagby, 2004).

Lane et al. (1997) hypothesize that the emotional response in subjects with high degrees of alexithymia is associated with impoverished conscious experience of emotion caused by an altered function of the anterior cingulate cortex (ACC).

This hypothesis fits in with functional imaging studies that support the crucial role of the ACC in emotional processing in healthy subjects and subjects with emotional disorders (Grimm et al., 2009, Lane et al., 1998, Larisch et al., 1997, Northoff et al., 2007, Reiman et al., 1997). There is evidence that morphological variations of the ACC might result in functional changes in subjects without apparent brain lesions (Vogt et al., 1995, Yucel et al., 2001, Yucel et al., 2002). Focusing on such structural changes Gundel et al. (2004) investigated a possible relationship between interindividual variability in ACC morphology and alexithymia using a Region of Interest (ROI)-based approach with manual tracing of the ACC on sagittal MRIs. They reported that subjects with low degrees of alexithymia tend to have a smaller ACC size than those with high degrees of alexithymia. In contrast, Borsci et al. (2009) using voxel-based morphometry (VBM) found that female high-alexithymic subjects compared to low-alexithymic subjects showed smaller gray matter volume in the ACC.

These contradictory findings could be attributed to methodological differences. Analyses with anatomically predefined ROIs are limited by focusing on preselected brain regions and the segmentation procedure is often arbitrary and poorly reproducible. In opposite, voxel-based methods (e.g. VBM) allow an unbiased (rater-independent) and comprehensive assessment of brain morphology without predefined regions. VBM is based on high resolution T1-weighted images and an automated segmentation procedure allowing the comparison of gray and white matter densities (or regional volumes) between groups.

Based on the results of the previous studies we tested the hypothesis of a difference in gray and white matter volume between low-alexithymic and high-alexithymic healthy men. In this regard the ACC was of special interest. Furthermore, in a previous study we demonstrated functional differences in the ACC using visual emotional stimuli. Contrasting high-alexithymic subjects with low-alexithymic subjects we observed increased activation of the ACC for different emotional valences as well as for different emotional stimuli. Furthermore, in a previous study we demonstrated functional differences in the ACC using visual emotional stimuli. Contrasting high-alexithymic subjects with low-alexithymic subjects we observed increased activation of the ACC for different emotional valences as well as for different emotional stimuli. Moreover, there was a positive correlation of the ACC with the individual TAS-20 scores (Heinzel et al., 2010).

Therefore, the main aim of the present study was to investigate if the altered functional anatomy is related to structural changes in the ACC. To that end we applied VBM and a ROI-based approach to the ACC. In addition we performed regression analysis with the clinical TAS-20 score. The hypothesis was tested against the null hypothesis of no difference among the groups in gray matter and in white matter.

Section snippets

Subjects

33 high- and 33 low-alexithymic male subjects were recruited by means of public announcements. Two low alexithymic subjects had to be excluded from the MRI measurements due to contraindications. Classification was based on the sum score of the Toronto Alexithymia Scale (German 20-item version, TAS-20 (Bach et al., 1996)). To account for the German population high and low alexithymia was defined a priori with reference to a random sample of adults (Franz et al., 2008). The 33rd (sum score = 45)

Results

The VBM analyses of gray and white matter revealed no differences between both groups (see also Table 2).

Using two-sample t-tests the comparisons of gray matter showed no significant differences (p < 0.05 FDR-corrected, whole brain analyses). Furthermore, we calculated a ROI-analysis using the same comparisons with an FDR-corrected p-level of p < 0.05 focusing on the ACC subsequent to a whole brain analysis (p < 0.001 uncorrected). No significant differences were found. Likewise, there was no

Discussion

We tested the hypothesis whether healthy male subjects with high and low degrees of alexithymia have white or gray matter volume differences in the ACC or not. According to our results the null hypothesis of no difference between the groups could not be rejected. Neither the subtraction nor the correlation analyses revealed significant differences between high- and low-alexithymic subjects.

Analyzing structural changes in alexithymia, Gundel et al. (2004) observed a positive relation between the

Role of funding source

The study was financially supported by a grant from the Forschungskommission der Medizinischen Fakultät of the Heinrich Heine Universität Düsseldorf to AH.

Conflict of interest

All authors declare that they have no conflicts of interest.

Acknowledgement

The authors are grateful to the financial support of the Forschungskommission der Medizinischen Fakultät of the Heinrich Heine Universität.

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      However, results relating ACC volume to alexithymia are ambiguous. For example, positive correlations between alexithymia and ACC surface have been reported (Gündel et al., 2004), while others reported lower volume in this area (Borsci et al., 2009; Ihme et al., 2013; Koven, Roth, Garlinghouse, Flashman, & Saykin, 2011; Paradiso, Vaidya, McCormick, Jones, & Robinson, 2008; Sturm & Levenson, 2011) or were unable to find any significant association (Heinzel et al., 2012). Furthermore, previous studies associated alexithymia with lower gray matter in the orbitofrontal cortex (OFC), insula, and amygdala (Borsci et al., 2009; Ihme et al., 2013), whereas another study reported increased volume in the insula associated with alexithymia (Zhang et al., 2011).

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