The study utilizes investigational software, the SPARK Test, with an FDA-cleared electroencephalography (EEG) amplifier and EEG cap to collect and patient EEG data.

The aim of this study is to collect data to support development of an algorithm to determine whether applying machine-learning techniques to eyes open/eyes closed resting-state electroencephalography (EEG) can characterize patient's cognitive status and detect the presence or absence of AD on the basis of the patient's EEG.

Inclusion Criteria:

1. Age 55 to 85 at the time of consent
2. Informant available and willing (remotely or in-person) to provide information about sleep patterns and cognitive functioning who spends >8 hours per week with primary subject
3. Subject or Legally Authorized Representative (LAR) has the ability to provide informed consent and comply with the protocol.

Exclusion Criteria:

1. Unable to remain still for up to 30 minutes during EEG data recording

2. Subjects currently on and unable to wash out concomitant medications, including: 1) opiates; 2) benzodiazepines and nonbenzodiazepine hypnotics; 3) sedative antihistamines; 4) tricyclic anti-depressants; 5) skeletal muscle relaxants; 6) antiepileptics; 7) antipsychotics; 8) antimanic agents; 9) THC; 10) anticholinergics

3. Previous history of craniotomy

4. Medical or psychiatric illness that would interfere with study participation

5. History of epilepsy or chronic seizure disorder

6. Presence of non-dental metal in head

7. Currently experiencing a skin disease on scalp that would affect electrode contacts

8. Subject meets at least one of the following criteria:

   1. Diagnosis of cognitive impairment from various underlying pathologies as indicated by one of the diagnostic codes listed in Appendix A (protocol)
   2. MMSE score of 27 or less
   3. Treating physician or PI have documented that the patient is cognitively impaired, with judgment of cognitive impairment having been made within the 6 months prior to enrollment

9. Substance Use Disorder, including Alcohol