title: P300 amplitude is insensitive to working memory load in schizophrenia.
abstract: BACKGROUND
  Working memory (WM) tasks usually elicit a P300 ERP component, whose amplitude decreases with increasing WM load. So far, this effect has not been studied in schizophrenics (SZs), a group that is considered to have an aberrant brain connectivity and impairments in WM capacity. The aim of this study was to determine the dependency of the P300 component on WM load in a sample of SZ subjects.
  
  
  METHODS
  We recorded 26 subjects (13 SZ patients and their matched controls) with an 80-channel electroencephalogram. Subjects performed an N-back task, a WM paradigm that manipulates the number of items to be stored in memory.
  
  
  RESULTS
  In healthy subjects, P300 amplitude was highest in the low WM load condition, and lowest in both the attentional control condition and the high WM load condition. In contrast, SZs evidenced low P300 amplitude in all conditions. A significant between group difference in P300 amplitude was evidenced only at the low WM load condition (1 -back), being smaller in SZs.
  
  
  CONCLUSIONS
  SZ subjects display a lower than normal P300 amplitude, which does not vary as a function of memory load. These results are consistent with a general impairment in WM capacity in these patients.
authors.affiliation: Clínica Psiquiátrica Universitaria, Hospital Clínico de la Universidad de Chile, Santiago, Chile. pgaspar@neuro.med.uchile.cl
authors.forename: Pablo A
authors.initials: PA
authors.lastname: Gaspar
authors.forename: Sergio
authors.initials: S
authors.lastname: Ruiz
authors.forename: Francisco
authors.initials: F
authors.lastname: Zamorano
authors.forename: Marcela
authors.initials: M
authors.lastname: Altayó
authors.forename: Carolina
authors.initials: C
authors.lastname: Pérez
authors.forename: Conrado A
authors.initials: CA
authors.lastname: Bosman
authors.forename: Francisco
authors.initials: F
authors.lastname: Aboitiz
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D002540:Cerebral Cortex / Q000503:physiopathology*; D004569:Electroencephalography; D018913:Event-Related Potentials, P300 / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D009483:Neuropsychological Tests; D012559:Schizophrenia / Q000503:physiopathology*; D012720:Severity of Illness Index