Interoception has been defined as the sensing of the physiological condition of the body, with interoceptive sensibility (IS) characterizing an individual's self-reported awareness of internal sensation. IS is a multidimensional construct including not only the tendency to be aware of sensation, but also how sensations are interpreted, regulated, and used to inform behavior, with different dimensions relating to different aspects of health and disease. Here we investigated neural mechanisms of interoception when healthy individuals attended to their heartbeat and skin temperature, and examined the relationship between neural activity during interoception and individual differences in self-reported IS using the Multidimensional Scale of Interoceptive Awareness (MAIA). Consistent with prior work, interoception activated a network involving insula and sensorimotor regions but also including occipital, temporal, and prefrontal cortex. Differences based on interoceptive focus (heartbeat vs. skin temperature) were found in insula, sensorimotor regions, occipital cortex, and limbic areas. Factor analysis of MAIA dimensions revealed 3 dissociable components of IS in our dataset, only one of which was related to neural activity during interoception. Reduced scores on the third factor, which reflected reduced ability to control attention to body sensation and increased tendency to distract from and worry about aversive sensations, was associated with greater activation in many of the same regions as those involved in interoception, including insula, sensorimotor, anterior cingulate, and temporal cortex. These data suggest that self-rated interoceptive sensibility is related to altered activation in regions involved in monitoring body state, which has implications for disorders associated with abnormality of interoception.

Subcortical volumetric changes in major depressive disorder (MDD) have been purported to underlie depressive symptomology, however, the evidence to date remains inconsistent. Here, we investigated limbic volumes in MDD, utilizing high-resolution structural images to allow segmentation of the hippocampus and amygdala into their constituent substructures. Twenty-four MDD patients and twenty matched controls underwent structural MRI at 7T field strength. All participants completed the Montgomery-Asberg Depression Rating Scale (MADRS) to quantify depressive symptomology. For the MDD group, volumes of the amygdala right lateral nucleus ( p = 0.05, r 2 = 0.24), left cortical nucleus ( p = 0.032, r 2 = 0.35), left accessory basal nucleus ( p = 0.04, r 2 = 0.28) and bilateral corticoamygdaloid transition area (right hemisphere p = 0.032, r 2 = 0.38, left hemisphere p = 0.032, r 2 = 0.35) each displayed significant negative associations with MDD severity. The bilateral centrocortical (right hemisphere p = 0.032, r 2 = 0.31, left hemisphere p = 0.032, r 2 = 0.32) and right basolateral complexes ( p = 0.05, r 2 = 0.24) also displayed significant negative relationships with depressive symptoms. Using high-field strength MRI, we report the novel finding that MDD severity is consistently negatively associated with amygdala nuclei, linking volumetric reductions with worsening depressive symptoms.

Background: Major Depressive Disorder (MDD) is an increasingly common and disabling illness. Since the amygdala has been reported to have pathological involvement in mood disorders, we aimed to investigate potential changes to structural connectivity of individual amygdala subnuclei in MDD for the first time, using ultra high-field 7T diffusion MRI.Methods: Twenty-four MDD patients (11 female) and twenty-four age-matched healthy control participants (7 female) underwent diffusion-weighted imaging with a 1.05mm isotropic resolution at 7 Tesla. Amygdala nuclei regions of interest were obtained through automated segmentation of 0.69mm resolution T1-weighted images and 0.35mm resolution T2-weighted images. Probabilistic tractography was performed on all subjects, with random seeding at each amygdala nucleus. Results:The right lateral, basal, central and centrocortical amygdala nuclei exhibited significantly increased connection density to the rest of the brain, whereas the left medial nucleus demonstrated significantly lower connection density (p FDR < 0.05). Increased connection density

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