Sleep Spindles Are Related to Schizotypal Personality Traits and Thalamic Glutamine/Glutamate in Healthy Subjects

Abstract

Background: Schizophrenia is a severe mental disorder affecting approximately 1% of the worldwide population. Yet, schizophrenia-like experiences (schizotypy) are very common in the healthy population, indicating a continuum between normal mental functioning and the psychosis found in schizophrenic patients. A continuum between schizotypy and schizophrenia would be supported if they share the same neurobiological origin. Two such neurobiological markers of schizophrenia are: (1) a reduction of sleep spindles (12-15 Hz oscillations during nonrapid eye movement sleep), likely reflecting deficits in thalamocortical circuits and (2) increased glutamine and glutamate (Glx) levels in the thalamus. Thus, this study aimed to investigate whether sleep spindles and Glx levels are related to schizotypal personality traits in healthy subjects. Methods: Twenty young male subjects underwent 2 all-night sleep electroencephalography recordings (128 electrodes). Sleep spindles were detected automatically. After those 2 nights, thalamic Glx levels were measured by magnetic resonance spectroscopy. Subjects completed a magical ideation scale to assess schizotypy. Results: Sleep spindle density was negatively correlated with magical ideation (r = −.64, P < .01) and thalamic Glx levels (r = −.70, P < .005). No correlation was found between Glx levels in the thalamus and magical ideation (r = .12, P > .1). Conclusions: The common relationship of sleep spindle density with schizotypy and thalamic Glx levels indicates a neurobiological overlap between nonclinical schizotypy and schizophrenia. Thus, sleep spindle density and magical ideation may reflect the anatomy and efficiency of the thalamo-cortical system that shows pronounced impairment in patients with schizophrenia.

Schizotypal traits are associated with sleep spindles and rapid eye movement in adolescence

“…It is possible that the continuum of schizotypy is related to some neural features that do not present a clinically significant risk of schizophrenia onset. One previous study (Lustenberger et al., ) reported a significant negative correlation between schizotypy and sleep spindle density in 20 healthy male subjects (mean age 23 years), as well as an increase in thalamic glutamine/glutamate, which is a marker for schizophrenia. These findings suggest a neurobiological overlap between schizophrenia and non‐clinical schizotypy.…”

Reduced Sleep Spindles in Schizophrenia: A Treatable Endophenotype That Links Risk Genes to Impaired Cognition?

“…In chronic medicated SZ, residual positive symptoms have not responded to dopaminergic medications and may arise from GABA or NMDA hypofunction (111), while in early untreated SZ, positive symptoms generally respond to APDs and may reflect dopamine hyperactivity (112). In healthy individuals, spindle density inversely correlates with magical ideation, an index of liability to delusional beliefs, and with glutamine and glutamate levels in the thalamus (113). Schizotypal traits, such as magical ideation, exist on a continuum in the general population and may share neural substrates with the psychotic symptoms of SZ.…”

Reduced sleep spindle density in early onset schizophrenia: A preliminary finding

“…The other study investigating spindle density in healthy adults showed that higher scores on a magical ideation scale, reflecting a proneness to delusion-like beliefs, were associated with a reduction in sleep spindle density. Hereby a continuum model was proposed, suggesting that unusual non-clinical beliefs may represent a milder form of the positive symptoms found in severe mental illness (Lustenberger et al, 2015). Interestingly, first studies in adults with other mental diseases such as major depression reveal increased spindle density values (Plante et al, 2013), supporting a possible disease-specific character of sleep spindles.…”