Elsevier

Biological Psychiatry

Volume 67, Issue 2, 15 January 2010, Pages 182-185
Biological Psychiatry

Brief Report
Reduced Orbitofrontal and Parietal Gray Matter in Chronic Insomnia: A Voxel-Based Morphometric Study

https://doi.org/10.1016/j.biopsych.2009.08.003Get rights and content

Background

Brain mechanisms of chronic insomnia, a highly prevalent condition, have barely been investigated. We demonstrate here a decrease in orbitofrontal gray matter (GM) volume that strongly correlates with the severity of complaints.

Methods

In a case-control study, optimized voxel-based morphometry was used to compare the regional brain volumes of 24 medication-free chronic primary insomnia patients (age range 52–74 years, 17 women), carefully selected to exclude psychiatric comorbidity, with those of 13 matched control subjects without sleep problems (age range 50–76 years, 9 women). Additionally, the correlation of regional volumes with insomnia severity was investigated.

Results

Patients had a smaller volume of GM in the left orbitofrontal cortex, strongly correlating (r = −.71) with the subjective severity of insomnia. Furthermore, reduced GM volume was found in the anterior and posterior precuneus. Patients did not show increased GM volume in any area. No group differences were found for white matter volume.

Conclusions

This is the first voxel-based morphometry study showing structural brain correlates of insomnia and their relation with insomnia severity. Functional roles of the affected areas in decision-making and stimulus processing might better guide future research into the poorly understood condition of insomnia.

Section snippets

Methods and Materials

Procedures complied with the declaration of Helsinki and were approved by the local medical ethics committee. Written informed consent was obtained from all participants.

Group Differences

Insomnia patients had a smaller volume of GM than control subjects in three areas (Supplement 1 and Figure 1A): first, the left orbitofrontal cortex (OFC), corresponding to Brodmann area (BA) 47; second, the bilateral anterior precuneus (BA 7) of the parietal cortex, extending to the transition area between the precuneus and primary somatosensory cortex (BA 1); third, the bilateral posterior precuneus (BA 7) in the occipitoparietal cortex. No areas of higher GM volume were found for the

Discussion

The current study is the first to apply voxel-based morphometry to quantitatively assess structural brain differences between carefully selected insomnia patients and matched control subjects. Insomnia subjects showed smaller GM volumes in three areas in the left orbitofrontal and parietal cortices. The functional importance of the left orbitofrontal GM is supported by the strong negative correlation of its volume with insomnia severity, without any correlation with mood ratings.

The

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