The association of interoceptive awareness and alexithymia with neurotransmitter concentrations in insula and anterior cingulate

Abstract

Alexithymia and increased interoceptive awareness have been associated with affective disorders as well as with altered insula and anterior cingulate cortex (ACC) function. Brain imaging studies have demonstrated an association between neurotransmitter function and affective disorders as well as personality traits. Here, we first examined the relationship between alexithymic facets as assessed with the Toronto Alexithymia Scale (TAS-20) and interoceptive awareness (assessed with the Body Perception Questionnaire) in 18 healthy subjects. Second, we investigated their association with glutamate and gamma-aminobutyric acid (GABA) concentrations in the left insula and the ACC using 3-Tesla proton magnetic resonance spectroscopy. Behaviorally, we found a close association between alexithymia and interoceptive awareness. Furthermore, glutamate levels in the left insula were positively associated with both alexithymia and awareness of autonomic nervous system reactivity, while GABA concentrations in ACC were selectively associated with alexithymia. Although preliminary, our results suggest that increased glutamate-mediated excitatory transmission-related to enhanced insula activity-reflects increased interoceptive awareness in alexithymia. Suppression of the unspecific emotional arousal evoked by increased awareness of bodily responses in alexithymics might thus be reflected in decreased neuronal activity mediated by increased GABA concentration in ACC.

Keywords: alexithymia; interoceptive awareness; neurotransmitter; proton magnetic resonance spectroscopy.

Fig. 1

Placement of the magnetic resonance spectroscopic voxel (orange frame) in (a) the ACC and (b) the left insula.

Fig. 2

Schematic representation of correlations between functional (dark gray) and behavioral markers (light gray) in (a) the ACC and (b) the left insula. There is a significant correlation between alexithymia (TAS-20) and awareness of autonomic nervous system reactivity (BPQ-ANS). Glutamate levels in left insula are positively associated with both alexithymia and awareness of autonomic nervous system reactivity, whereas GABA concentrations in ACC are associated with alexithymia, but not with interoceptive awareness. TAS-20, Toronto Alexithymia Scale; BPQ, Body Perception Questionnaire; ANS, Awareness of Autonomous Nervous System Reactivity and ACC, anterior cingulate cortex.

Fig. 3

Bar diagrams show (a) glutamate and (b) GABA concentrations in ACC and insula in subjects scoring high and low, respectively, on the TAS-20. Differences in glutamate concentration between these two groups were observed in insula (P < 0.05), but not ACC, whereas differences in GABA concentration were observed in ACC (P < 0.07), but not in insula. TAS-20, Toronto Alexithymia Scale; ACC, anterior cingulate cortex. *P < 0.05.