i. Ages 45-80 (inclusive) ii. Adequate sensorimotor function (including motor function of dominant hand to complete CCT) and verbal expressive abilities to complete all assessments. iii. Access to reliable Wi-Fi and a Bluetooth-enabled mobile phone or tablet with internet connection capable of supporting study procedures. iv. Self-reported change in cognitive functioning (e.g., memory, attention, thinking abilities) compared to prior functioning, persisting ≥ 6 months and associated with concern and/or impact on daily functioning. v. Is on fixed pharmacotherapy (i.e. stable dose of medication/s) for ≥ 4 weeks before enrollment, and expected to remain stable throughout study participation. This includes, but is not limited to, cholinesterase inhibitors, NMDA receptor antagonists, and antidepressants.

i. Prior diagnosis of Mild Cognitive Impairment or Dementia (NIA-AA) or Mild or Major Neurocognitive Disorder (DSM-5). ii. taVNS contraindications (e.g., history of seizures, history of trauma or damage to ear, reduced/impaired sensation in the ear). iii. MRI contraindications (e.g., ferromagnetic implants, claustrophobia). iv. Presence of a neurological, medical, or psychiatric condition that is acute, unstable, or severe, and that, in the judgment of the study investigators, would significantly interfere with safe participation, valid assessment of cognition or mood, or interpretation of study outcomes. v. Enrolled in a clinical trial or has received an investigational medication or device in the last 30 days that may impact cognition or mood. vi. For female participants, a positive pregnancy test if still menstruating within the past 12 months.