J Psychiatry Neurosci 2019;44(4):261-268 | PDF
Jee In Kang, MD, PhD; Deog Young Kim, MD, PhD; Chang-il Lee, MD; Chan-Hyung Kim, MD, PhD; Se Joo Kim, MD, PhD
Background: Deficits in cortical inhibitory processes have been suggested as underlying pathophysiological mechanisms of obsessive–compulsive disorder (OCD). We examined whether patients with OCD have altered cortical excitability using paired-pulse transcranial magnetic stimulation (TMS). We also tested associations between TMS indices and OCD-related characteristics, including age of onset and response inhibition in the go/no-go paradigm, to examine whether altered cortical excitability contributes to symptom formation and behavioural inhibition deficit in patients with OCD.
Methods: We assessed motor cortex excitability using paired-pulse TMS in 51 patients with OCD and 39 age-matched healthy controls. We also assessed clinical symptoms and response inhibition in the go/no-go task. All patients were undergoing treatment with serotonin reuptake inhibitors. We performed repeated-measures multivariate analysis of covariance to compare TMS indices between patients with OCD and controls.
Results: Compared to controls, patients with OCD showed a shorter cortical silent period and decreased intracortical facilitation. However, we found no significant difference between groups for resting motor threshold or short-interval intracortical inhibition. In the OCD group, the shortened cortical silent period was associated with a prompt reaction time in the go/no-go task and with early onset of OCD.
Limitations: We could not exclude the influence of medications on motor cortex excitability.
Conclusion: These findings suggest abnormal cortical excitability in patients with OCD. The associations between cortical silent period and response inhibition and age of onset further indicate that altered cortical excitability may play an important role in the development of OCD.
Submitted Apr. 24, 2018; Revised Aug. 6, 2018; Accepted Sept. 6, 2018; Published online Feb. 13, 2019
Acknowledgements: This study was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Education (NRF-2015R1D1A1A09058829).
Affiliations: From the Department of Psychiatry and Institute of Behavioral Science in Medicine, Yonsei University College of Medicine, Seoul, South Korea (Kang, C. Kim, S.J. Kim); the Department and Research Institute of Rehabilitation Medicine, Yonsei University College of Medicine, Seoul, South Korea (D.Y. Kim); and the Yonsei Phil Neuropsychiatric Clinic, Seoul, South Korea (Lee).
Competing interests: None declared.
Contributors: J.I. Kang, D.Y. Kim and S.J. Kim designed the study. All authors acquired the data, which J.I. Kang and S.J. Kim analyzed. J.I. Kang 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.J. Kim, Department of Psychiatry, Yonsei University College of Medicine, 50-1 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea; firstname.lastname@example.org