title: Structural correlates of trait impulsivity in patients with bipolar disorder and healthy controls: a surface-based morphometry study.
abstract: BACKGROUND
  Patients with bipolar disorder (BD) frequently exhibit impulsive behaviors independent of their mood state, and trait impulsivity is increasingly recognized as a crucial BD biomarker. This study aimed to investigate structural correlates of trait impulsivity measured using the Barratt Impulsiveness Scale (BIS) in healthy controls (HCs) and patients with BD.
  
  
  METHODS
  We recruited 59 patients diagnosed with BD I or BD II (35.3 ± 8.5 years) and 56 age- and sex-matched HCs (33.9 ± 7.4 years). Participants underwent structural magnetic resonance imaging and clinical evaluations, and their BIS scores were evaluated. An automated surface-based method (FreeSurfer) was used to measure cortical thickness and generate thickness maps for each participant. Brain-wise regression analysis of the association between cortical thickness and BIS scores was performed separately for BD and HC groups by using a general linear model.
  
  
  RESULTS
  Patients with BD obtained significantly higher BIS scores than HCs. In HCs, higher BIS scores were associated with a thinner cortex in the left inferior, middle and medial frontal cortices. By contrast, in BD patients, higher BIS scores were associated with a thicker cortex in the right insula. Patients with BD showed a thinner cortex than HCs in all these four structures.
  
  
  CONCLUSIONS
  The findings indicate that the left prefrontal cortex plays a cardinal role in trait impulsivity of healthy individuals. Patients with BD have a different structural correlate of trait impulsivity in the right insula. However, the use of various psychotropics in patients with BD may limit our interpretation of BD findings.
authors.affiliation: Department of Medical Research,Taipei Veterans General Hospital,Taipei 112,Taiwan.
authors.forename: P C
authors.initials: PC
authors.lastname: Tu
authors.affiliation: Institute of Brain Science, National Yang-Ming University,Taipei,Taiwan.
authors.forename: Y H
authors.initials: YH
authors.lastname: Kuan
authors.affiliation: Department of Psychiatry,Taipei Veterans General Hospital,Taipei 112,Taiwan.
authors.forename: C T
authors.initials: CT
authors.lastname: Li
authors.affiliation: Department of Psychiatry,Taipei Veterans General Hospital,Taipei 112,Taiwan.
authors.forename: T P
authors.initials: TP
authors.lastname: Su
mesh_terms: D000328:Adult; D001714:Bipolar Disorder / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology; D002540:Cerebral Cortex / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000473:pathology; D005260:Female; D006801:Humans; D007175:Impulsive Behavior / Q000502:physiology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D010551:Personality / Q000502:physiology*; D017397:Prefrontal Cortex / Q000033:anatomy & histology / Q000000981:diagnostic imaging
keywords: Cortical thickness; surface-based methods; trait impulsivity