title: Reduced but broader prefrontal activity in patients with schizophrenia during n-back working memory tasks: a multi-channel near-infrared spectroscopy study.
abstract: BACKGROUND
  Caudal regions of the prefrontal cortex, including the dorsolateral (DLPFC) and ventrolateral (VLPFC) prefrontal cortex, are involved in essential cognitive functions such as working memory. In contrast, more rostral regions, such as the frontopolar cortex (FpC), have integrative functions among cognitive functions and thereby contribute crucially to real-world social activity. Previous functional magnetic resonance imaging studies have shown patients with schizophrenia had different DLPFC activity pattern in response to cognitive load changes compared to healthy controls; however, the spatial relationship between the caudal and rostral prefrontal activation has not been evaluated under less-constrained conditions.
  
  
  METHODS
  Twenty-six patients with schizophrenia and 26 age-, sex-, and premorbid-intelligence-matched healthy controls participated in this study. Hemodynamic changes during n-back working memory tasks with different cognitive loads were measured using multi-channel near-infrared spectroscopy (NIRS).
  
  
  RESULTS
  Healthy controls showed significant task-related activity in the bilateral VLPFC and significant task-related decreased activity in the DLPFC, with greater signal changes when the task required more cognitive load. In contrast, patients with schizophrenia showed activation in the more rostral regions, including bilateral DLPFC and FpC. Neither decreased activity nor greater activation in proportion to elevated cognitive load occurred.
  
  
  CONCLUSIONS
  This multi-channel NIRS study demonstrated that activation intensity did not increase in patients with schizophrenia associated with cognitive load changes, suggesting hypo-frontality as cognitive impairment in schizophrenia. On the other hand, patients had broader prefrontal activity in areas such as the bilateral DLPFC and FpC regions, thus suggesting a hyper-frontality compensatory response.
authors.affiliation: Department of Neuropsychiatry, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo 113-8655, Japan. skoike-tky@umin.ac.jp
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Koike
authors.forename: Ryu
authors.initials: R
authors.lastname: Takizawa
authors.forename: Yukika
authors.initials: Y
authors.lastname: Nishimura
authors.forename: Masaru
authors.initials: M
authors.lastname: Kinou
authors.forename: Shingo
authors.initials: S
authors.lastname: Kawasaki
authors.forename: Kiyoto
authors.initials: K
authors.lastname: Kasai
mesh_terms: D000328:Adult; D001931:Brain Mapping; D016022:Case-Control Studies; D005260:Female; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D008297:Male; D008569:Memory Disorders / Q000209:etiology*; D008570:Memory, Short-Term / Q000502:physiology*; D008875:Middle Aged; D009483:Neuropsychological Tests; D017397:Prefrontal Cortex / Q000378:metabolism / Q000503:physiopathology*; D012559:Schizophrenia / Q000150:complications* / Q000473:pathology*; D019265:Spectroscopy, Near-Infrared; D013223:Statistics as Topic
chemical_list: D006454:Hemoglobins
keywords: Frontopolar prefrontal cortex; Hierarchical network; Near-infrared spectroscopy (NIRS); Schizophrenia; Working memory