Impairment of sleep-related memory consolidation in schizophrenia: relevance of sleep spindles?
OBJECTIVE
Deficits in declarative memory performance are among the most severe neuropsychological impairments in schizophrenia and contribute to poor clinical outcomes. The importance of sleep for brain plasticity and memory consolidation is widely accepted, and sleep spindles seem to play an important role in these processes. The aim of this study was to test the associations of sleep spindles and picture memory consolidation in patients with schizophrenia and healthy controls.


METHODS
We studied 16 patients with schizophrenia on stable antipsychotic medication (mean age ± standard deviation, 29.4 ± 6.4 years) and 16 healthy controls matched for age and educational level. Sleep was recorded and scored according to American Academy of Sleep Medicine (AASM) standard criteria. We performed a picture recognition paradigm and compared recognition performance for neutral and emotional pictures in sleep and wake conditions.


RESULTS
Recognition accuracy was better in healthy controls than in patients with schizophrenia in the sleep and wake conditions. However, the memory-promoting effect of sleep was significantly lower in schizophrenia patients than in controls. Sleep spindle activity was reduced in patients, and sleep spindle density was correlated with sleep-associated facilitation of recognition accuracy for neutral pictures.


CONCLUSIONS
Reduced sleep spindles seem to play an important role as a possible mechanism or biomarker for impaired sleep-related memory consolidation in patients with schizophrenia, and are a new target for treatment to improve memory functions and clinical outcomes in these patients.
Department of Psychiatry and Psychotherapy, University Hospital Schleswig-Holstein, Kiel, Germany. Electronic address: robert.goeder@uksh.de.
Robert
R
Göder
Department of Psychiatry and Psychotherapy, University Hospital Schleswig-Holstein, Kiel, Germany.
Anna
A
Graf
Department of Psychiatry and Psychotherapy, University Hospital Schleswig-Holstein, Kiel, Germany.
Felix
F
Ballhausen
Department of Psychiatry and Psychotherapy, University Hospital Schleswig-Holstein, Kiel, Germany.
Sara
S
Weinhold
Department of Psychiatry and Psychotherapy, University Hospital Schleswig-Holstein, Kiel, Germany.
Paul Christian
PC
Baier
Department of Psychiatry and Psychotherapy, University Hospital Schleswig-Holstein, Lübeck, Germany.
Klaus
K
Junghanns
Department of Adolescent and Child Psychiatry and Psychotherapy, University Hospital Schleswig-Holstein, Kiel, Germany.
Alexander
A
Prehn-Kristensen
D000328:Adult; D001921:Brain / Q000503:physiopathology; D016022:Case-Control Studies; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008297:Male; D000069077:Memory Consolidation / Q000502:physiology*; D008569:Memory Disorders / Q000209:etiology; D017286:Polysomnography; D021641:Recognition, Psychology / Q000502:physiology; D012559:Schizophrenia / Q000150:complications / Q000503:physiopathology*; D012890:Sleep / Q000502:physiology*; D055815:Young Adult
Memory; Picture recognition; Schizophrenia; Sleep spindle