Abstract
BackgroundDown syndrome (DS) is the most common genetic cause of intellectual disability (ID) worldwide. Understanding electrophysiological characteristics associated with DS provides potential mechanistic insights into ID, helping inform biomarkers and targets for intervention. Currently, electrophysiological characteristics associated with DS remain unclear due to methodological differences between studies and inadequate controls for cognitive decline as a potential cofounder.MethodsEyes-closed resting-state EEG measures (specifically delta, theta, alpha, and beta absolute and relative powers, and alpha peak amplitude, frequency and frequency variance) in occipital and frontal regions were compared between adults with DS (with no diagnosis of dementia or evidence of cognitive decline) and typically developing (TD) matched controls (n = 25 per group).ResultsWe report an overall ‘slower’ EEG spectrum, characterised by higher delta and theta power, and lower alpha and beta power, for both regions in people with DS. Alpha activity in particular showed strong group differences, including lower power, lower peak amplitude and greater peak frequency variance in people with DS.ConclusionsSuch EEG ‘slowing’ has previously been associated with cognitive decline in both DS and TD populations. These findings indicate the potential existence of a universal EEG signature of cognitive impairment, regardless of origin (neurodevelopmental or neurodegenerative), warranting further exploration.
Highlights
Down syndrome (DS) is caused by an extra copy of chromosome 21 and is the most common genetic cause of intellectual disability (ID) worldwide, affecting 1 in 800 births [1]
Resting-state electroencephalography (EEG) paradigms provide a general measure of brain activity
That brain rhythms may operate across a wider frequency range than these discrete categories, with substantial intersubject variability [5]
Summary
Down syndrome (DS) is caused by an extra copy of chromosome 21 and is the most common genetic cause of intellectual disability (ID) worldwide, affecting 1 in 800 births [1]. As resting-state paradigms are passive, they are inherently free from the need for participants to understand and retain task instructions (e.g. pressing a Hamburg et al Journal of Neurodevelopmental Disorders (2021) 13:48 button in response to a target), reducing any confounding influences of individual differences in ID level and motor skills [3]. It is posited that these mechanisms enable the brain to integrate a large number of distributed local processes into global states [4] Such brain rhythms are characterised by distinct frequency bands, associated with differing underlying mechanisms of generation and brain functions; typically, delta (< 4 Hz), theta (4-8 Hz), alpha (8-13 Hz), beta (13-30 Hz) and gamma (> 30 Hz). Electrophysiological characteristics associated with DS remain unclear due to methodological differences between studies and inadequate controls for cognitive decline as a potential cofounder
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