title: Hyperthymic temperament and brightness judgment in healthy subjects: involvement of left inferior orbitofrontal cortex.
abstract: BACKGROUND
  Hyperthymic temperament has been generally accepted as one of premorbid temperament of bipolar disorders. Since recent several studies indicate an association between illuminance and hyperthymic temperament, it can be hypothesized that more hyperthymic temperament subjects have a different threshold of brightness or darkness perception in comparison with less hyperthymic temperament subjects.
  
  
  METHODS
  We compared the threshold of brightness and darkness judgment between more and less hyperthymic subjects, and by simultaneously using fMRI we compared activations of whole brain between these subjects by two sample t-test. Furthermore, the association between the activations and hyperthymic temperament scores was analyzed.
  
  
  RESULTS
  Although there was no significant difference in the threshold of brightness or darkness judgment between more and less hyperthymic subjects, there was a significant difference in activations of the regions including left superior temporal gyrus, left inferior orbitofrontal cortex, left triangular inferior frontal gyrus and left insula between these subjects. Moreover, there was a significantly positive association between a cluster containing left inferior orbitofrontal cortex and hyperthymic temperament scores. The common activated region of these two analyses (categorical and continuous ones) was determined as left inferior orbitofrontal cortex.
  
  
  CONCLUSIONS
  Limitation of the present study is a lack of brightness and darkness preference experiment between more and less hyperthymic subjects.
  
  
  CONCLUSIONS
  The present findings suggest that the threshold of brightness and darkness judgment is not different between more and less hyperthymic subjects, and that hyperthymic temperament may be associated with left inferior orbitofrontal cortex, which has been reported to be associated with bipolar disorder.
authors.affiliation: Department of Neuropsychiatry, Oita University Faculty of Medicine, Oita, Japan.
authors.forename: Mayu
authors.initials: M
authors.lastname: Harada
authors.forename: Nobuhiko
authors.initials: N
authors.lastname: Hoaki
authors.forename: Takeshi
authors.initials: T
authors.lastname: Terao
authors.forename: Koji
authors.initials: K
authors.lastname: Hatano
authors.forename: Kentaro
authors.initials: K
authors.lastname: Kohno
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Araki
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Mizokami
authors.forename: Kensuke
authors.initials: K
authors.lastname: Kodama
authors.forename: Koji
authors.initials: K
authors.lastname: Toyokawa
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Izumi
authors.forename: Miyano
authors.initials: M
authors.lastname: Arasaki
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Shimomura
authors.forename: Minoru
authors.initials: M
authors.lastname: Fujiki
authors.forename: Takanori
authors.initials: T
authors.lastname: Kochiyama
mesh_terms: D000328:Adult; D000339:Affect / Q000502:physiology; D001714:Bipolar Disorder / Q000503:physiopathology*; D001921:Brain / Q000502:physiology; D003624:Darkness; D005260:Female; D005625:Frontal Lobe; D059907:Functional Neuroimaging; D006801:Humans; D007600:Judgment / Q000502:physiology; D008027:Light; D008279:Magnetic Resonance Imaging; D008297:Male; D010775:Photic Stimulation; D012684:Sensory Thresholds; D013694:Temperament; D014796:Visual Perception; D055815:Young Adult
keywords: Brightness; Healthy subjects; Hyperthymic temperament; fMRI