Young people living with a genetic mutation that increases their risk of psychiatric disorders have different brain activity during sleep, a new study shows, with genes from about 30 genes on 22q11.2DS chromosome 22. It is caused by deletion and occurs in 1 in 3000 births. , It increases the risk of intellectual disability, autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD) and epileptic seizures.
It is one of the biggest biological risk factors for schizophrenia. However, the biological mechanisms underlying psychotic symptoms in 22q11.2DS remain unclear. “We have recently shown that the majority of youth with 22q11.2DS have sleep problems, particularly insomnia and sleep fragmentation, which are associated with psychiatric disorders,” said co-senior author Marianne van den Bree, at Cardiff University. Professor of Psychological Medicine. , Britain.
“However, our previous analysis was based on reporting by parents on their children’s sleep quality, and the neurophysiology of what is happening with brain activity is yet to be explored.” An established method of measuring brain activity during sleep is the electroencephalogram (EEG).
It measures electrical activity during sleep and consists of patterns called spindle and slow-wave (SW) oscillations. These features are hallmarks of non-rapid eye movement (NREM) sleep and are thought to aid in memory consolidation and brain development. “Since the sleep EEG is known to be altered in several neurodevelopmental disorders, the properties and coordination of these changes can be used as biomarkers for psychiatric disease” Lead Clinical Lecturer in General Adult Psychiatry at the University of Bristol, UK Writer Nick Donnelly explained.
To detect this in 22q11.2DS, the team recorded a nightly sleep EEG in 28 youth aged 6-20 years with a chromosome deletion and in 17 unaffected siblings, as part of the Cardiff University Experience of Children. recruited with copy number variants in (ECHO) Studies, Prof. Under the leadership of van den Bree. They measured correlations between sleep EEG patterns and psychiatric symptoms, as well as performance in a recall test the next morning.
They found that the group with 22q11.2DS had significant changes in sleep patterns, including N3 NREM sleep (slow-wave sleep) and a lower proportion of N1 (the first and lightest sleep stages) and rapid eye movement (REM) sleep . , compared to their siblings.
Those carrying chromosome deletions also had increased EEG power for both slow-wave oscillations and spindles. There was also an increase in the frequency and density of the spindle pattern in the 22q112.DS group and the strong coupling between the spindle and slow-wave EEG features. These changes may reflect changes in the relationships within and between the areas of the brain that generate these oscillations, the cortex and the thalamus.
Participants also took part in a pre-sleep 2D object location task, where they had to remember where the matching cards were on the screen. They were tested again in the morning on the same task, and the team found that in people with 22q11.2DS, higher axis and SW amplitudes were associated with lower accuracy. In contrast, in participants without chromosomal deletions, higher amplitudes were associated with higher accuracy in the morning recall test.
Finally, the team estimated the effect of differences in sleep patterns on psychotic symptoms in the two groups using a statistical method called mediation.
They calculated the total effect of genotype on psychiatric measures and IQ, the indirect (mediated) effect of EEG measures, and then the proportion of the total effect that could be mediated by EEG patterns.
They found that the effects on anxiety, ADHD and ASD driven by the 22q11.2 deletion were partially mediated by sleep EEG differences. “Our EEG findings together suggest a complex picture of sleep neurophysiology in 22q11.2DS and highlight differences that may serve as potential biomarkers for the neurodevelopmental syndrome associated with 22q11.2DS,” said co-authors. Senior author Matt Jones, Professorial Research Fellow in Neuroscience, University, concluded. of Bristol, UK.
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“Further studies will now be needed to elucidate the relationship between psychotic symptoms, sleep EEG measures, and neurodevelopment, to pinpoint markers of brain circuit dysfunction that can inform doctors which patients are most at risk.” and support treatment decisions.”