title: Semantic clustering of category fluency in schizophrenia examined with singular value decomposition.
abstract: Decreased productivity on verbal fluency tasks by persons with schizophrenia has been attributed to semantic system abnormalities. Semantic structure is often assessed using multidimensional scaling (MDS) to detect normal and aberrant semantic clustering. However, MDS has limitations that may be particularly problematic for such assessments. Here, we introduce a different clustering technique, singular value decomposition (SVD), to elucidate abnormalities of the semantic system in schizophrenia. We compared 102 treated outpatients with schizophrenia to 109 healthy adults on two category-cued word fluency tasks. Patients with schizophrenia showed semantic clustering patterns that differ markedly from those of healthy adults. However, SVD revealed more detailed and critical semantic system abnormalities than previously appreciated using MDS. Patients with schizophrenia showed less coherent semantic clustering of both low- and high-frequency category exemplars than healthy adults. These results suggest the intriguing possibility that impaired automatic activation of semantic information is a key deficit in schizophrenia.
authors.affiliation: Department of Neurology, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors.forename: Kyongje
authors.initials: K
authors.lastname: Sung
authors.forename: Barry
authors.initials: B
authors.lastname: Gordon
authors.forename: Tracy D
authors.initials: TD
authors.lastname: Vannorsdall
authors.forename: Kerry
authors.initials: K
authors.lastname: Ledoux
authors.forename: Erin J
authors.initials: EJ
authors.lastname: Pickett
authors.forename: Godfrey D
authors.initials: GD
authors.lastname: Pearlson
authors.forename: David J
authors.initials: DJ
authors.lastname: Schretlen
mesh_terms: D000328:Adult; D016000:Cluster Analysis; D005260:Female; D006801:Humans; D007806:Language Disorders / Q000209:etiology*; D007807:Language Tests; D008297:Male; D008875:Middle Aged; D010700:Phonetics; D012559:Schizophrenia / Q000150:complications*; D012660:Semantics; D014705:Verbal Behavior