1. Brain volume differences between healthy females with high and low emphatic behavior
Ch. Berger1 , M. Fleischer2, L. Schulze3, K. Prehn4, G. Domes5
1Department of Child and Adolescent Psychiatry, 2Department of Psychiatry and Psychotherapy, University Medicine Rostock, Germany, 3Free University of Berlin, 4Charité University Medicine Berlin, 5Department of Psychology, University of Freiburg
Material & Methods
We explored structural differences in GM volume between the high empathic (HE) and the low empathic (LE) group with magnetic resonance imaging (MRI) [2].
Study sample (Fig.1): 25. and 75. percentile were taken from 269 female healthy students completing the Empathy Quotient (EQ [3]), resulting in 20 individuals with EQ > 45 (age mean ±SD: 22.8±2.24) and 20 age-matched individuals with an EQ < 35 (age mean ±SD: 23.1±1.62).
MRI acquisition: 1.5 T Siemens AVANTO, 1mm, isotropic- t1-weighted sequence (MPRAGE)
GM volumetric assessment: SPM8 and VBM8-toolboxes for MATLAB.
Preprocessing: MPRAGE-images -> brain-tissue segmented ->GM maps-> high-dimensional spatial MNI-normalized (IXI-template, VBM8).
Statistical analysis:
Region-of-interest-based (ROI): Extraction of ROI-wise sum of GM volume (weighted with total incranial volume (TIV)) (ROIs were associated to empathy as reported in the literature [1]). Statistical analysis with SPSS, significance level p < .05.
Voxelwise ANCOVA: diagnosis (variable of interest), TIV (confound). Statistical analysis with SPM8, significance level p < .005 (uncorrected), minimum cluster size =20 contiguous voxels, masked for GM probability of 0.1 in the reference template.
Introduction
Empathizing is the ability to identify the mental states of others, for predicting their behavior and responding with appropriate emotion. Two routes to empathy are discussed [1]: One relatively automatically process, with fast emotional responding and late appraisal. A second way is less automatic with early cognitive appraisal. Brain areas with structural changes related to empathy comprising regions from the mirror neuron system (MNS) and the default mode network (DMN). Positive and negative associations between empathizing and regional gray matter (GM) volume were found in healthy controls in the left inferior frontal gyrus (IFG), insula and superior temporal sulcus. Facing these divergent correlative effects, we compared GM volume of healthy females with low and high empathic behavior.
Results
In the region-of-interest-based analysis, none of the regions was showing a significant group difference.
Exploratory voxelwise analysis (Tab. 1):
Contrast HE>LE (Fig.2): Clusters of reduced GM volume in the LE group were found in right and more prominent in left frontal, bilateral occipital and temporal regions, comprising the left middle and superior frontal gyrus, the right middle and inferior temporal gyrus, the bilateral IFG, fusiform gyrus, lingual gyrus and cerebellum.
Contrast LE>HE (Fig.3):
For the HE group, the most prominent cluster of reduced GM volume comprising the right parahippocampus, temporal inferior gyrus and cerebellum. Another cluster was consisting of voxels from the left insula, superior temporal gyrus, rolandic operculum and superior part of temporal pole and clusters were also found in the right caudate and less pronounced in the left middle occipital lobe and in the right superior medial frontal gyrus.
Bild
Bild
Bild
frequency
Empathy Quotient Score(mean±sd) 39.7±7.7
Fig. 2
GM volume differences: high EQ > low EQ, p=0.005 (uncorrected), clustersize = 20 voxels
Fig. 3
GM volume differences: low EQ > high EQ, p=0.005 (uncorrected), clustersize = 20 voxels
Fig. 1
Total sample EQ histogram
Tab. 1
Summary of clusters of voxelwise GM volume group differences
Label
x,y,z in mm
nb voxel in cluster
peak t-value (uncorr)
high EQ > low EQ
Left/right: fusif., lingual gyrus, cerebelum /
742/267
4.06/3.68
Left: Frontal middle and superior gyrus /
163/447
3.41/3.23
Right: Temporal inferior and mid. gyrus
225
3.17
Left IFG /
104/115
3.16/3.04
Right IFG 53
3.18
low EQ > high EQ
Right: Temporal inferior and Parahippocampal gyrus
472
4.11
Left: Occipital mid., sup. gyrus
227
3.95
Left: Insula, temp. sup., rolandic oper., temp. sup. pole
169
3.38
Left: Insula
113
2.97
Engen, H.G. and T. Singer, Empathy circuits. Curr Opin Neurobiol, (2): p
Bertsch, K., et al., Brain volumes differ between diagnostic groups of violent criminal offenders. Eur Arch Psychiatry Clin Neurosci, (7): p
S Baron-Cohen, S Wheelwright. The Empathy Quotient: An Investigation Of Adults With Asperger Syndrome Or High Functioning Autism And Normal Sex Differences. 34(2): J Autism Dev Disord   2004.
Conclusion
We did not find any group effects in the region-of-interest-based analysis. Most likely are variations in normal empathic behaviour in healthy individuals associated with only localized sub-regional brain structure differences. Indeed, the exploratory voxel-wise approach revealed, that both groups show different clusters of altered GM volume on the voxel level. The HE group showed increased GM volume in frontal regions, comprising MNS and in lateral occipital and temporal regions associated with social recognition. Analysis revealed for the LE group increased GM volume in the left insula and right parahippocampal gyrus, more related to reconstructive empathy.
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