Cortical Disarray Measurement in Mild Cognitive Impairment and Alzheimer's Disease

PATIENT PARTICIPANTS Inclusion Criteria: * Diagnosis of mild cognitive impairment (MCI) or prodromal Alzheimer's Disease (AD) as defined by National Institute on Ageing/Alzheimer's Association (NIA/AA) diagnostic criteria for MCI/prodromal AD, NOT including MCI unlikely due to AD; OR, Diagnosis of Alzheimer's disease as defined by NIA/AA criteria for probable AD * Clinical dementia rating (CDR) scale global score of very mild or mild (0.5 or 1) impairment * Ability to undergo and tolerate MRI scans, with no contraindications to MRI * Ability to tolerate blood draws * Ability to give informed consent to participate in the study Exclusion Criteria: * Do not meet the inclusion criteria * No study companion available * Individuals with a non-progressive learning disability * Pregnant or intending to become pregnant during the study COMPANION PARTICIPANTS Inclusion Criteria: * Aged over 18 years * Sufficient knowledge on study participant's condition to complete companion assessments of the patient, in the investigator's judgement * Able and willing to attend all clinical visits for completion of companion assessments or provide the relevant assessments remotely via phone or video call Exclusion Criteria: * A condition or reason, in the investigator's judgement, that would question the validity of the acquired companion reported data * Individuals who are not fluent in English