title: Graph Theoretical Analysis of Structural Neuroimaging in Temporal Lobe Epilepsy with and without Psychosis.
abstract: OBJECTIVE
  Psychosis is one of the most important psychiatric comorbidities in temporal lobe epilepsy (TLE), and its pathophysiology still remains unsolved. We aimed to explore the connectivity differences of structural neuroimaging between TLE with and without psychosis using a graph theoretical analysis, which is an emerging mathematical method to investigate network connections in the brain as a small-world system.
  
  
  METHODS
  We recruited 11 TLE patients with unilateral hippocampal sclerosis (HS) presenting psychosis or having a history of psychosis (TLE-P group). As controls, 15 TLE patients with unilateral HS without any history of psychotic episodes were also recruited (TLE-N group). For graph theoretical analysis, the normalized gray matter images of both groups were subjected to Graph Analysis Toolbox (GAT). As secondary analyses, each group was compared to 14 age- and gender-matched healthy subjects.
  
  
  RESULTS
  The hub node locations were found predominantly in the ipsilateral hemisphere in the TLE-N group, and mainly on the contralateral side in the TLE-P group. The TLE-P group showed significantly higher characteristic path length, transitivity, lower global efficiency, and resilience to random or targeted attack than those of the TLE-N group. The regional comparison in betweenness centrality revealed significantly decreased connectivity in the contralateral temporal lobe, ipsilateral middle frontal gyrus, and bilateral postcentral gyri in the TLE-P group. The healthy subjects showed well-balanced nodes/edges distributions, similar metrics to TLE-N group except for higher small-worldness/modularity/assortativity, and various differences of regional betweenness/clustering.
  
  
  CONCLUSIONS
  In TLE with psychosis, graph theoretical analysis of structural imaging revealed disrupted connectivity in the contralateral hemisphere. The network metrics suggested that the existence of psychosis can bring vulnerability and decreased efficiency of the whole-brain network. The sharp differences in structural networks between morphologically homogeneous groups are remarkable and may contribute to a better understanding of psychosis in TLE.
authors.affiliation: Department of Radiology, National Center of Neurology and Psychiatry, Tokyo, Japan.|Department of Neuropsychiatry, Graduate School of Medicine, the University of Tokyo, Tokyo, Japan.
authors.forename: Daichi
authors.identifier: http://orcid.org/0000-0001-9617-706X
authors.initials: D
authors.lastname: Sone
authors.affiliation: Integrative Brain Imaging Center, National Center of Neurology and Psychiatry, Tokyo, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Matsuda
authors.affiliation: Department of Mental Disorder Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan.
authors.forename: Miho
authors.initials: M
authors.lastname: Ota
authors.affiliation: Integrative Brain Imaging Center, National Center of Neurology and Psychiatry, Tokyo, Japan.
authors.forename: Norihide
authors.initials: N
authors.lastname: Maikusa
authors.affiliation: Department of Radiology, National Center of Neurology and Psychiatry, Tokyo, Japan.
authors.forename: Yukio
authors.initials: Y
authors.lastname: Kimura
authors.affiliation: Department of Radiology, National Center of Neurology and Psychiatry, Tokyo, Japan.
authors.forename: Kaoru
authors.initials: K
authors.lastname: Sumida
authors.affiliation: Department of Radiology, National Center of Neurology and Psychiatry, Tokyo, Japan.
authors.forename: Kota
authors.initials: K
authors.lastname: Yokoyama
authors.affiliation: Integrative Brain Imaging Center, National Center of Neurology and Psychiatry, Tokyo, Japan.
authors.forename: Etsuko
authors.initials: E
authors.lastname: Imabayashi
authors.affiliation: Department of Psychiatry, National Center of Neurology and Psychiatry, Tokyo, Japan.
authors.forename: Masako
authors.initials: M
authors.lastname: Watanabe
authors.affiliation: Department of Psychiatry, National Center of Neurology and Psychiatry, Tokyo, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Watanabe
authors.affiliation: Department of Psychiatry, National Center of Neurology and Psychiatry, Tokyo, Japan.
authors.forename: Mitsutoshi
authors.initials: M
authors.lastname: Okazaki
authors.affiliation: Department of Radiology, National Center of Neurology and Psychiatry, Tokyo, Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Sato
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D004569:Electroencephalography; D004833:Epilepsy, Temporal Lobe / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology; D005260:Female; D006624:Hippocampus / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009415:Nerve Net / Q000000981:diagnostic imaging / Q000503:physiopathology; D059906:Neuroimaging / Q000379:methods*; D011618:Psychotic Disorders / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology; D013702:Temporal Lobe / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology