data collection based on this study will allow us to collect and calibrate neurophysiological and cognitive data collected from in-ear EEG recordings of the initial baseline/reference population in Swiss healthy individuals that can be used as reference to data collected in other populations, for instance, to be compared with any other similar dataset in the future (e.g., Alzheimer patient cohorts).

There is solid neurophysiological evidence indicating that abnormal brain rhythms during sleep and noradrenergic dysfunction are core components of cognitive decline and AD onset, and their related pathophysiology. Crucially, irregularities in these neurophysiological mechanisms appear to occur in an asymptomatic and pre-symptomatic stage, but their potential to identify susceptibility for triggering neurodegeneration has yet to be established.

Thus, the possibility to identify such risk biomarkers in humans will require the acquisition of large-scale data related direct or indirect measurements of these physiological signatures. A possible key source to obtain such large-scale data related to sleep and noradrenergic function is the assessment of electroencephalographic recordings through non-obtrusive, low-cost, and reliable wearable sensors, alongside the use of advanced neuro-computational algorithms that link brain function and behavioral outcomes of LC function via pupilometry measurements.

Participants fulfilling all of the following inclusion criteria are eligible for the study:

• Informed Consent as documented by signature

• Healthy young adults group: Age range 20-40

• Healthy older adults group: Age range 50-75

• Normal physical and mental status:

  • Diseases or lesions of the nervous system (acute or residual included neurological and psychiatric diseases)
  • Clinically significant concomitant disease states (e.g., renal failure, hepatic dysfunction, cardiovascular disease, etc.)
  • Sleep disorders, known or suspected (e.g. Insomnia, sleep apnoea, restless leg syndrome, narcolepsy, etc.)
  • mini mental state examination (MMSE) score > 24)

• Native German speaker or good understanding of German

Participants are not eligible if the fulfil the following exclusion criteria:

• Direct relatives have not been diagnosed with neuropathological conditions associated with any form of dementia (e.g., AD, MCI)
• Participation in another study with investigational drug/therapy/interventions within the 30 days preceding and during the present study (start date adapted accordingly)
• Shift-work (e.g. work times 12am-5am)
• Suspected drug- or medication abuse, or on-label sleep medication use during time of the study
• Infection/disease of auditory canal or ear drum that could worsen with EAR-DREAM application, or allergies to in-Ear electrode materials (e.g., silver)
• Pregnancy (not safety related, but relevant for data interpretation procedures given that pregnancy can result in sleep patterns that are different from the baseline measurements that we intend to characterize) Additional non-medical exclusion criteria may be defined for certain cognitive tasks (e.g. no glasses during experiments involving pupillometry).

Data will be collected in healthy young adults (age range 20-40) and healthy older adults (age range 50-75).