title: Gamma oscillation in functional brain networks is involved in the spontaneous remission of depressive behavior induced by chronic restraint stress in mice.
abstract: BACKGROUND
  Depression is one of the most prevalent mood disorders, and is known to be associated with abnormal functional connectivity in neural networks of the brain. Interestingly, a significant proportion of patients with depression experience spontaneous remission without any treatment. However, the relationship between electroencephalographic (EEG) functional connectivity and the spontaneous remission in depression remains poorly understood. Here, we investigated regional and network brain activity using EEG signals from a chronic restraint stress (CRS)-induced mouse model of depression. After 1 (CRS1W) or 3 weeks (CRS3W) following the cessation of a 4-week-long CRS, mice were subjected to depression-associated behavioral tasks. EEG signals were obtained from eight cortical regions (frontal, somatosensory, parietal, and visual cortices in each hemisphere).
  
  
  RESULTS
  The CRS1W group exhibited behavioral dysfunctions in the open field and forced swim tasks, whereas the CRS3W group displayed normal levels of behaviors in those tasks. In a linear correlation analysis, the CRS1W group exhibited increased correlation coefficient values at all frequency bands (delta, 1.5-4; theta, 4-8; alpha, 8-12; beta, 12-30; gamma, 30-80 Hz) compared with the control group. However, the differences in delta- and gamma-frequency bands between the control and CRS1W groups were no longer observed in the CRS3W group. Persistent brain network homology revealed significantly different functional connectivity between the control and CRS1W groups, and it demonstrated a huge restoration of the decreased distances in the gamma-frequency band for the CRS3W group. Moreover, the CRS3W group displayed a similar strength of connectivity among somatosensory and frontal cortices as the control group.
  
  
  CONCLUSIONS
  A mouse model of CRS-induced depression showed spontaneous behavioral remission of depressive behavior. Using persistent brain network homology analysis of EEG signals from eight cortical regions, we found that restoration of gamma activity at the network level is associated with behavioral remission.
authors.affiliation: Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong, Daejeon, 305-701, Republic of Korea. celestialcld@gmail.com.
authors.forename: Arshi
authors.initials: A
authors.lastname: Khalid
authors.affiliation: Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong, Daejeon, 305-701, Republic of Korea. qudtjs1988@kaist.ac.kr.
authors.forename: Byung Sun
authors.initials: BS
authors.lastname: Kim
authors.affiliation: Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong, Daejeon, 305-701, Republic of Korea. boamida@hanmail.net.
authors.forename: Bo Am
authors.initials: BA
authors.lastname: Seo
authors.affiliation: Laboratory for Neurotherapeutics, Department of Neurology, Comprehensive Epilepsy Center, Biomedical Research Institute, Seoul National University Hospital (SNUH), 101 Daehak-ro, Jongno-gu, Seoul, 110-744, Republic of Korea. staelee@gmail.com.
authors.forename: Soon-Tae
authors.initials: ST
authors.lastname: Lee
authors.affiliation: Laboratory for Neurotherapeutics, Department of Neurology, Comprehensive Epilepsy Center, Biomedical Research Institute, Seoul National University Hospital (SNUH), 101 Daehak-ro, Jongno-gu, Seoul, 110-744, Republic of Korea. jungkh@gmail.com.
authors.forename: Keun-Hwa
authors.initials: KH
authors.lastname: Jung
authors.affiliation: Laboratory for Neurotherapeutics, Department of Neurology, Comprehensive Epilepsy Center, Biomedical Research Institute, Seoul National University Hospital (SNUH), 101 Daehak-ro, Jongno-gu, Seoul, 110-744, Republic of Korea. stemcell.snu@gmail.com.
authors.forename: Kon
authors.initials: K
authors.lastname: Chu
authors.affiliation: Laboratory for Neurotherapeutics, Department of Neurology, Comprehensive Epilepsy Center, Biomedical Research Institute, Seoul National University Hospital (SNUH), 101 Daehak-ro, Jongno-gu, Seoul, 110-744, Republic of Korea. sangkun2923@gmail.com.
authors.forename: Sang Kun
authors.initials: SK
authors.lastname: Lee
authors.affiliation: Laboratory for Neurotherapeutics, Department of Neurology, Comprehensive Epilepsy Center, Biomedical Research Institute, Seoul National University Hospital (SNUH), 101 Daehak-ro, Jongno-gu, Seoul, 110-744, Republic of Korea. clark.jeon@gmail.com.|Advanced Neural Technologies, Ihwhajang-gil 71, Jongno-gu, Seoul, 03087, Republic of Korea. clark.jeon@gmail.com.
authors.forename: Daejong
authors.initials: D
authors.lastname: Jeon
mesh_terms: D000818:Animals; D058256:Brain Waves; D002540:Cerebral Cortex / Q000503:physiopathology*; D003866:Depressive Disorder / Q000209:etiology / Q000503:physiopathology*; D004195:Disease Models, Animal; D004569:Electroencephalography; D065818:Gamma Rhythm; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009043:Motor Activity; D009434:Neural Pathways / Q000503:physiopathology; D012075:Remission, Spontaneous; D012149:Restraint, Physical; D013315:Stress, Psychological / Q000150:complications*