ADMCI participants showed reduced reactivity of individual alpha power between wakefulness and light sleep stages compared to controls, while periodic and aperiodic signatures of sleep onset were relatively preserved, suggesting selective vulnerability of attentional thalamocortical systems in prodromal AD.
Key Findings
Results
ADMCI patients showed reduced reactivity of individual alpha power during the transition from quiet wakefulness to light sleep compared to cognitively unimpaired older adults.
EEG datasets of approximately 30 minutes were analyzed from 19 ADMCI patients and 18 matched cognitively unimpaired older adults (controls).
Vigilance stages were scored using a reduced version of Hori's system, distinguishing the alpha-dominant wakefulness stage and the theta-dominant light sleep (ripples) stage.
EEG spectra were parameterized using the specparam algorithm.
The reduced alpha reactivity in ADMCI suggests disrupted vigilance regulation at the prodromal stage of Alzheimer's disease.
Results
Both ADMCI and control groups showed comparable increases in fronto-central theta power during the transition from wakefulness to the light sleep (ripples) stage.
The theta-dominant ripples stage represents light sleep onset in Hori's vigilance scoring system.
The comparable theta power increases between groups indicate that periodic signatures of sleep onset are relatively preserved in ADMCI.
This finding suggests that the neural mechanisms generating frontal theta activity during sleep onset are not selectively disrupted in prodromal AD.
Results
Both ADMCI and control groups exhibited comparable steepening of the aperiodic EEG slope and offset during the transition from wakefulness to light sleep.
The aperiodic EEG component is described as reflecting global cortical arousal.
No group differences emerged in aperiodic exponent and offset between ADMCI and control participants.
The authors note that statistical power was limited by the modest sample size of 19 ADMCI and 18 control participants.
This finding is consistent with prior reports that the aperiodic rsEEG component remains unchanged in AD dementia.
Results
Aperiodic rsEEG signatures of sleep onset (slope and offset changes) were preserved in ADMCI, indicating that global cortical arousal dynamics during vigilance transitions remain intact.
The study is described as exploratory given the modest sample sizes.
The aperiodic component, reflecting global cortical arousal, showed comparable changes across groups during vigilance transitions.
The preservation of aperiodic dynamics contrasts with the disrupted periodic alpha reactivity observed in ADMCI.
Discussion
The pattern of disrupted alpha reactivity but preserved theta and aperiodic signatures during sleep onset suggests selective vulnerability of attentional thalamocortical systems in prodromal AD.
Alpha band disruptions (8–12 Hz) are interpreted as reflecting impaired vigilance regulation in ADMCI.
The authors describe the overall pattern as indicating 'selective vulnerability of attentional thalamocortical systems.'
Resting-state eyes-closed EEG was used, with datasets approximately 30 minutes in duration.
The study extends prior findings from AD dementia to the prodromal (mild cognitive impairment) stage.
What This Means
This research suggests that people in the early stages of Alzheimer's disease (called mild cognitive impairment, or MCI) show a specific pattern of abnormal brain activity as they transition from wakefulness into light sleep. Using EEG brain recordings lasting about 30 minutes, researchers compared 19 individuals with MCI due to Alzheimer's disease against 18 healthy older adults. They focused on how brain rhythms changed as participants moved from an alert, wakeful state into early sleep. The key finding was that the Alzheimer's MCI group showed a much smaller change in alpha brain waves (the rhythms associated with calm, alert wakefulness) during this transition, suggesting their brains are less able to properly regulate states of alertness and attention.
Importantly, not all brain activity patterns were disrupted. The slower theta brain waves associated with the onset of light sleep increased similarly in both groups, and a broader measure of brain arousal called the 'aperiodic' EEG component also changed in the same way for both groups as they drifted toward sleep. This means the basic machinery for falling asleep appears to be relatively intact in early Alzheimer's disease, while the systems specifically responsible for maintaining and regulating wakefulness are impaired.
This research suggests that in the prodromal (early) stage of Alzheimer's disease, the brain circuits involved in attention and vigilance — particularly those connecting the thalamus and cortex and operating through alpha rhythms — are selectively damaged. This could help explain why early Alzheimer's patients often have trouble sustaining attention. The authors caution that this was an exploratory study with a small sample size, and larger studies are needed to confirm these findings.
Carpi M, Henao Isaza V, Noce G, Salamone E, Del Percio C, Lopez S, et al.. (2026). Periodic and Aperiodic Electroencephalographic Rhythms During Vigilance Transitions in Alzheimer's Disease Mild Cognitive Impairment.. Annals of the New York Academy of Sciences. https://doi.org/10.1111/nyas.70194