Barbara Hrast1, Gašper Zupan1,2, Andrej Vovk1, and Dušan Šuput1
1Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia, 2Institute of Radiology, University Medical Centre Ljubljana, Ljubljana, Slovenia
Synopsis
This study
investigated the association between alterations in cerebral
morphology and neuroticism. Grey matter thickness, cortical area, and
volume were calculated in 110 healthy right-handed subjects and
correlations with neuroticism scores performed. Negative correlations
between neuroticism and cortical area/volume and positive
correlations between neuroticism and grey matter thickness were found
in occipitotemporal regions. The importance of the ventral visual
pathway in emotion processing has been highlighted by structural
changes in the occipital and temporal lobe. Alterations in the
prefrontal cortex also show the importance emotional control plays in
neuroticism. This study provided an additional explanation of
structural alterations in neuroticism.
Introduction
Neuroticism is one of the Big Five
personality1 traits, and
it correlates to the frequency and duration of negative emotions2.
Previous research has shown a significant negative association
between total brain volume and neuroticism. Individual differences in
stress reactivity, vulnerability to life stressors, negative affect,
and emotional
instability might contribute to reductions in brain volume observed
during adulthood3.
It is also speculated that high scoring individuals might perceive
situations as more stressful than others, and also respond more
inadequately to stressors4.
Moreover, neuroticism
was shown to be correlated with alterations of cortical surfaces4
and cortical thickness5-8.
Alterations in volume of different brain regions6,9-14 and
changes
in cortical folding8,15
have also been demonstrated in individuals with high neuroticism. Our
study aims to uncover more specific alterations of cerebral
morphology in correlation with the neuroticism score and tries to
provide a comprehensive explanation of neural correlates.Methods
Grey matter thickness (GMT),
cortical area, and volume were calculated in 110 healthy right-handed subjects
(43 females) with a mean age of 43.9 +/- 15.9. High-resolution T1 gradient echo
and T2-weighted turbo spin-echo pulse sequences were performed on all participants,
and they were tested with Big Five Inventory (BFI) personality test16,
which was used for calculating neuroticism score. The
following parameters were used in T1-weighted and T2-weighted images,
respectfully: TE: 5.9
ms/403 ms, TR: 12 ms/2500 ms, matrix: 320x336/320x336, flip angle: 8°/90°,
field of view: 224x235/224x235, voxel dimension: 0.7x0.7x0.7/0.7x0.7x0.7,
number of slices in sagittal: 236/236, number of averages: 2/2 and acquisition
time: 11 min 55 sec/6min 58 sec. Correlations between GMT, cortical
area, volume, and neuroticism were investigated. Cortical reconstruction and
volumetric segmentation were performed using Freesurfer image analysis suite
6.0 (Boston, MA, USA). GMT, cortical area, and volume were modeled in
Freesurfer's QDEC interface with neuroticism as covariate and age as the
nuisance factor. All the maps were smoothed with an
FWHM 10 mm kernel. In the analysis, correlations between GMT, volume,
cortical area, and neuroticism were explored in all subjects. Automatic
algorithm produced regions at the level of statistical significance p<0.05 , afterward
correction for multiple comparisons (CMC) was applied in Freesurfer by performing
Monte Carlo Simulation at p<0.05.Results
Significant positive
association between GMT and neuroticism was found in bilateral
fusiform gyri, precunei, cunei, precentral gyri (preCG), postcentral
gyri (postCG), superior parietal gyri (SPG), inferior parietal gyri
(IPG), posterior cingulate cortices (PCC), lateral occipital cortices
(LOC), inferior temporal gyri (ITG), LG, left pars opercularis,
medial frontal gyrus (MFG), superior frontal gyrus (SFG),
parahippocampal gyrus (PHG), entorhinal cortex (EC) and right insula,
supramarginal gyrus (SMG), superior temporal gyrus (STG) and medial
temporal gyrus (MTG). The results are represented in Figure 1. On the
other hand, significant negative relationship was found between
cortical area and neuroticism bilaterally in the insula, lateral
orbitofrontal cortex (latOFC) and pars opercularis, left STG, preCG,
postCG, SMG, MTG, LOC, and fusiform gyrus. Analysis of correlation
between volume and neuroticism yielded negative associations in left
IPG, LOC, and ITP and no locations in the right hemisphere (Figure
2).Discussion
Structural changes in
the occipital lobe and temporal lobe demonstrate the importance of
the ventral visual pathway in processing emotional signals17.
These findings suggest that high scoring individuals might perceive
situations as more stressful than others. Therefore they are more
impacted by stress, which has been shown to be deleterious for brain
morphology3,18.
Our results support the involvement of the prefrontal cortex in
emotional control in neuroticism19.
We also demonstrated an essential role of LPC and latOFC in emotion
regulation, as shown in the previous studies20.Conclusions
This study
corroborated previous findings on structural brain alterations in
individuals with high neuroticism but also managed to provide an
additional explanation to why the alterations appear in occipital
lobe and temporal lobe. Future research could look into the ventral
visual pathway and its relationship to neuroticism and possible ways
to lessen the negative effects it has on mental health.Acknowledgements
The
study was financially supported by The Slovenian Research Agency.
Authors declare no conflict of interest.References
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