title: Functional abnormalities in the left ventrolateral prefrontal cortex during a semantic fluency task, and their association with thought disorder in patients with schizophrenia.
abstract: Thought disorder is one of the primary symptoms in schizophrenia, yet the neural correlates and related semantic processing abnormalities remain unclear. We aimed to investigate the relationship between functional prefrontal abnormalities and thought disorder in schizophrenia using 2 types of verbal fluency tasks: the letter fluency task (LFT) and the category fluency task (CFT). Fifty-six adult patients with schizophrenia and 56 healthy controls matched for age, gender, and IQ participated in the study. During completion of the 2 types of verbal fluency tasks, we measured oxy- and deoxy-hemoglobin concentration ([oxy-Hb] and [deoxy-Hb]) signal changes over a wide area of the bilateral prefrontal cortex, using a 52-channel near-infrared spectroscopy (NIRS) system. Thought disorder scores were evaluated using the positive and negative syndrome scale. CFT performance was significantly higher than LFT performance in both groups, while there was no significant difference in any prefrontal NIRS signal changes between the 2 tasks in either group. In both versions of verbal fluency task, healthy controls exhibited a significantly greater NIRS signal change than did patients with schizophrenia. On the CFT only, left ventrolateral prefrontal NIRS [deoxy-Hb] signals were significantly associated with thought disorder scores in patients with schizophrenia. Our results suggest that left ventrolateral prefrontal abnormalities in category fluency might be related to thought disorder in schizophrenia. This could lead to an improved understanding of the neural mechanisms within the left ventrolateral prefrontal cortex involved in mediating semantic processing, as well as the relationship between semantic processing abnormalities and thought disorder in schizophrenia.
authors.affiliation: Department of Neuropsychiatry, Graduate School of Medicine, The University of Tokyo, Tokyo 113-8655, Japan.
authors.forename: Kohei
authors.initials: K
authors.lastname: Marumo
authors.forename: Ryu
authors.initials: R
authors.lastname: Takizawa
authors.forename: Masaru
authors.initials: M
authors.lastname: Kinou
authors.forename: Shingo
authors.initials: S
authors.lastname: Kawasaki
authors.forename: Yuki
authors.initials: Y
authors.lastname: Kawakubo
authors.forename: Masato
authors.initials: M
authors.lastname: Fukuda
authors.forename: Kiyoto
authors.initials: K
authors.lastname: Kasai
mesh_terms: D000328:Adult; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D059907:Functional Neuroimaging; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D017397:Prefrontal Cortex / Q000503:physiopathology*; D011597:Psychomotor Performance / Q000502:physiology; D012559:Schizophrenia / Q000503:physiopathology*; D012565:Schizophrenic Psychology; D012660:Semantics; D019265:Spectroscopy, Near-Infrared; D013850:Thinking / Q000502:physiology
chemical_list: D006454:Hemoglobins
keywords: Near-infrared spectroscopy (NIRS); Prefrontal hemodynamic response; Schizophrenia; Semantic processing abnormality; Thought disorder; Verbal fluency task (VFT)