title: Reduction of cortical GABAergic inhibition correlates with working memory impairment in recent onset schizophrenia.
abstract: BACKGROUND
  Cognitive impairments are present during the early course of schizophrenia, and the contribution of GABAergic dysfunction to these cognitive impairments has received increasing attention. Cortical GABAergic inhibition can be assessed using short-interval intracortical inhibition (SICI) in a paired-pulse transcranial magnetic stimulation (ppTMS). The aim of this study was to examine the relationship between cortical GABAergic inhibition and cognitive function in recent onset schizophrenia patients using ppTMS and a neuropsychological battery.
  
  
  METHODS
  The subjects were 20 healthy controls (HC group) and 20 patients with schizophrenia whose duration of illness was less than three years (SZ group). All subjects underwent ppTMS measurements of SICI and intracortical facilitation (ICF), and cognitive performance of the SZ group was assessed using the Brief Assessment of Cognition in Schizophrenia Japanese-language version. We examined group differences in ppTMS measurements (resting motor threshold, SICI, and ICF). In the SZ group, we assessed the relationship between SICI and cognitive performance, and the relationships between SICI and age, duration of illness, medications, and psychopathology.
  
  
  RESULTS
  The SZ group showed a significant reduction of SICI compared to the HC group, and demonstrated a significant correlation between the reduction of SICI and impaired performance of a working memory task. The HC and the SZ groups did not differ significantly in resting motor threshold and ICF. The SZ group did not show any significant correlations between SICI and age, duration of illness, medications, or psychopathology.
  
  
  CONCLUSIONS
  Our results suggest that the reduction of cortical GABAergic inhibition is related to impairment of working memory in patients with recent onset schizophrenia.
authors.affiliation: Department of Neuropsychiatry, Wakayama Medical University, Wakayama, Japan. t-shun@wakayama-med.ac.jp
authors.forename: Shun
authors.initials: S
authors.lastname: Takahashi
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ukai
authors.forename: Asami
authors.initials: A
authors.lastname: Kose
authors.forename: Tadahiro
authors.initials: T
authors.lastname: Hashimoto
authors.forename: Jun
authors.initials: J
authors.lastname: Iwatani
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Okumura
authors.forename: Tomikimi
authors.initials: T
authors.lastname: Tsuji
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Shinosaki
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D014150:Antipsychotic Agents / Q000494:pharmacology / Q000627:therapeutic use; D001569:Benzodiazepines / Q000494:pharmacology / Q000627:therapeutic use; D002540:Cerebral Cortex / Q000503:physiopathology*; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000187:drug effects; D005260:Female; D006801:Humans; D008297:Male; D008569:Memory Disorders / Q000209:etiology*; D008570:Memory, Short-Term / Q000502:physiology*; D009044:Motor Cortex / Q000187:drug effects; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D009483:Neuropsychological Tests; D011569:Psychiatric Status Rating Scales; D012559:Schizophrenia / Q000150:complications* / Q000188:drug therapy / Q000473:pathology*; D012565:Schizophrenic Psychology; D050781:Transcranial Magnetic Stimulation; D014706:Verbal Learning / Q000187:drug effects / Q000502:physiology; D055815:Young Adult
chemical_list: D014150:Antipsychotic Agents; D001569:Benzodiazepines