J Psychiatry Neurosci 2018;43(6):366-374
Jae Myeong Kang, MD*; Sung Woo Joo, MD*; Young-Don Son, PhD; Hyun Kim, MS; Kwang-Pil Ko, MD, PhD; Jung Sun Lee, MD, PhD†; Seung-Gul Kang, MD, PhD†
Background: Previous studies have reported functional and structural abnormalities in the thalamus and the pars triangularis of the inferior frontal gyrus in patients with insomnia disorder. However, no studies have been conducted on the white-matter tracts between these 2 brain regions. We aimed to compare the white-matter integrity and structure of the left thalamus–pars triangularis tracts between patients with insomnia and controls, and to characterize the relationship between white-matter integrity and clinical features in patients with insomnia.
Methods: In total, 22 participants with insomnia disorder and 27 controls underwent overnight polysomnography and brain magnetic resonance imaging, and then completed self-report clinical questionnaires and neurocognitive tests for spatial planning. Structural and diffusion measures such as fractional anisotropy, axial diffusivity, radial diffusivity and trace were analyzed in group comparison and correlation analyses.
Results: The insomnia group showed significantly lower fractional anisotropy (F = 8.647, p = 0.02) and axial diffusivity (F = 5.895, p = 0.038) in the left thalamus–pars triangularis tracts than controls. In patients with insomnia, fractional anisotropy in the tracts was correlated with the results of the Stockings of Cambridge test (r = 0.451, p = 0.034), and radial diffusivity was correlated with Epworth Sleepiness Scale score (r = 0.437, p = 0.042).
Limitations: Limitations included analyses of limited brain regions and the cross-sectional design.
Conclusion: The insomnia group showed decreased integrity in the left thalamus–pars triangularis tracts, and integrity was correlated with cognition and daytime sleepiness. These results may imply that insomnia is characterized by disintegration of the white-matter tract between the left thalamus and inferior frontal gyrus.
*Share first authorship.
Submitted Oct. 3, 2017; Revised Dec. 29, 2017; Revised Jan. 31, 2018; Accepted Feb. 22, 2018; Published online June 12, 2018
Acknowledgments: This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Education (NRF-2017R1D1A1B03032431). It was also supported by a grant from the Korea Health Technology R&D Project through the Korea Health Industry Development Institute, funded by the Ministry of Health and Welfare, Republic of Korea (grant number : HI17C2665).
Affiliations: From the Department of Psychiatry, Gil Medical Center, Gachon University, College of Medicine, Incheon, Republic of Korea (Kang, Kang); Department of Psychiatry, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Republic of Korea (Joo, Lee); Department of Biomedical Engineering, College of Health Science, Gachon University, Incheon, Republic of Korea (Son); Department of Psychological and Brain Sciences, Boston University, Boston, MA, United States (Kim); and Department of Preventive Medicine, Gachon University, College of Medicine, Incheon, Republic of Korea (Ko).
Competing interests: None declared.
Contributors: J. Lee and S.-G. Kang designed the study. J. Kang and S.-G. Kang acquired the data, which all authors analyzed. J. Kang and S. Joo wrote the article, which all authors reviewed. All authors approved the final version to be published and can certify that no other individuals not listed as authors have made substantial contributions to the paper.
Correspondence to: S. Kang, Department of Psychiatry, Gil Medical Center, Gachon University, College of Medicine, 21, Namdong-daero 774 beon-gil, Namdong-gu, Incheon, 21565, Republic of Korea; firstname.lastname@example.org; J. Lee, Department of Psychiatry, University of Ulsan College of Medicine, Asan Medical Center, 88, Olympic-ro 43-gil, Songpa-gu, Seoul, 05505, Republic of Korea; email@example.com