Abstract
Objective: Alexithymia relates to difficulties recognizing and describing emotions. It has been linked to subjectively increased interoceptive awareness (IA) and to psychiatric illnesses such as major depressive disorder (MDD) and somatization. MDD in turn is characterized by aberrant emotion processing and IA on the subjective as well as on the neural level. However, a link between neural activity in response to IA and alexithymic traits in health and depression remains unclear.Methods: A well-established fMRI task was used to investigate neural activity during IA (heartbeat counting) and exteroceptive awareness (tone counting) in non-psychiatric controls (NC) and MDD. Firstly, comparing MDD and NC, a linear relationship between IA-related activity and scores of the Toronto Alexithymia Scale (TAS) was investigated through whole-brain regression. Secondly, NC were divided by median-split of TAS scores into groups showing low (NC-low) or high (NC-high) alexithymia. MDD and NC-high showed equally high TAS scores. Subsequently, IA-related neural activity was compared on a whole-brain level between the three independent samples (MDD, NC-low, NC-high).Results: Whole-brain regressions between MDD and NC revealed neural differences during IA as a function of TAS-DD (subscale difficulty describing feelings) in the supragenual anterior cingulate cortex (sACC; BA 24/32), which were due to negative associations between TAS-DD and IA-related activity in NC. Contrasting NC subgroups after median-split on a whole-brain level, high TAS scores were associated with decreased neural activity during IA in the sACC and increased insula activity. Though having equally high alexithymia scores, NC-high showed increased insula activity during IA compared to MDD, whilst both groups showed decreased activity in the sACC.Conclusions: Within the context of decreased sACC activity during IA in alexithymia (NC-high and MDD), increased insula activity might mirror a compensatory mechanism in NC-high, which is disrupted in MDD.
Highlights
Alexithymia is a multifaceted personality construct characterized by individuals having difficulties identifying or describing feelings
Comparing Patients Suffering from Major Depressive Disorder (MDD, n = 16) to Non-Psychiatric Controls (NC, n = 30) (Figure 1) and Determination of nonpsychiatric controls (NC) Subgroups Firstly, we investigated whether a linear relationship between neural activity (IA vs. implicit baseline or exteroceptive awareness (EA) vs. implicit baseline) and the association between alexithymia (TAS) scores differed between the two groups
16 major depressive disorder (MDD) patients were compared to the total group of 30 NC, i.e., this group was not classified according to their alexithymic state yet
Summary
Alexithymia is a multifaceted personality construct characterized by individuals having difficulties identifying or describing feelings. The described triangular interconnection between alexithymia, bodily awareness and depressive symptoms (see Harshaw, 2015 for review) is evident in the general population (see Honkalampi et al, 2000 on depression and alexithymia; see Mattila et al, 2008 on alexithymia and somatization) This supports the view of alexithymia being a relatively stable personality trait (Luminet et al, 2001; Saarijarvi et al, 2006; Stingl et al, 2008) and emphasizes the need for more investigations in non-psychiatric participants. Despite these strong relationships between alexithymic traits and major depression, both of which include aberrant emotional and body awareness, the association between neural activity in response to body awareness and alexithymic traits in health and depression remains to be described
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