title: Impairment in semantic retrieval is associated with symptoms in schizophrenia but not bipolar disorder.
abstract: BACKGROUND
  The Semantic Object Retrieval Task (SORT) requires participants to indicate whether word pairs recall a third object. Schizophrenia individuals (SZ) tend to report associations between nonassociated word pairs; this overretrieval is related to formal thought disorder (FTD). Since semantic memory impairments and psychosis are also found in bipolar disorder (BP), we examined whether SORT impairments and their relationship to symptoms are also present in BP.
  
  
  METHODS
  Participants (n = 239; healthy control subjects [HC] = 133; BP = 32; SZ = 74) completed SORT while undergoing functional magnetic resonance imaging (fMRI) scanning.
  
  
  RESULTS
  Retrieval accuracy negatively correlated with negative symptoms and no-retrieval accuracy negatively correlated with FTD severity in SZ but not BP. Retrieval versus no-retrieval trials activated a distributed fronto-parieto-temporal network; bilateral inferior parietal lobule (IPL) activity was larger in HC versus SZ and HC versus BP, with no difference in SZ versus BP. Right IPL activity positively correlated with positive and general psychosis symptoms in SZ but not BP.
  
  
  CONCLUSIONS
  SZ reported more associations between unrelated word pairs than HC; this overretrieval increased with FTD severity. Schizophrenia individuals were also more likely to fail to find associations between related word pairs; this underretrieval increased with negative symptom severity. fMRI symptom correlations in IPL in SZ are consistent with arguments that IPL abnormality relates to loosening of associations in SZ. By comparison, BP showed intermediate impairments on SORT, uncorrelated with symptoms, suggesting that the relationship between SORT performance, fMRI activity, and psychotic symptoms is schizophrenia-specific.
authors.affiliation: Olin Neuropsychiatry Research Center, Institute of Living, Hartford, Connecticut 06106, USA. sharna.jamadar@monash.edu
authors.forename: Sharna
authors.initials: S
authors.lastname: Jamadar
authors.forename: Kasey M
authors.initials: KM
authors.lastname: O'Neil
authors.forename: Godfrey D
authors.initials: GD
authors.lastname: Pearlson
authors.forename: Mahvesh
authors.initials: M
authors.lastname: Ansari
authors.forename: Adrienne
authors.initials: A
authors.lastname: Gill
authors.forename: Kanchana
authors.initials: K
authors.lastname: Jagannathan
authors.forename: Michal
authors.initials: M
authors.lastname: Assaf
mesh_terms: D000328:Adult; D001714:Bipolar Disorder / Q000150:complications / Q000503:physiopathology / Q000523:psychology*; D016022:Case-Control Studies; D003072:Cognition Disorders / Q000150:complications* / Q000503:physiopathology / Q000523:psychology; D005260:Female; D059907:Functional Neuroimaging; D006801:Humans; D008297:Male; D011939:Mental Recall; D009483:Neuropsychological Tests; D010296:Parietal Lobe / Q000503:physiopathology; D012559:Schizophrenia / Q000150:complications* / Q000503:physiopathology*; D012565:Schizophrenic Psychology; D012660:Semantics