• Community-dwelling adults
• Age ≥75 years
• English or Spanish as primary language
• Clinically evident cardiovascular disease defined as prior myocardial Infarction (MI), prior stroke, prior revascularization procedure, or a secondary prevention indication for a statin (clinician determined)
• Hospitalization for a primary diagnosis of heart failure in the prior 12 months (Note: History of heart failure in the absence of recent hospitalization or clinically evident cardiovascular disease is not an exclusion)
• Dementia (clinically evident or previously diagnosed)
• Dependence in any Katz Basic Activities of Daily Living [ADL] (with the exception of urinary or bowel continence)
• Severe hearing impairment (preventing phone follow up)
• Unable to talk (preventing phone follow up)
• Severe visual impairment (preventing cognitive testing)
• Statin use in the past year or for longer than 5 years previously (participant reported)
• Ineligible to take atorvastatin 40 mg (clinician determined)
• Documented intolerance to statins
• Active Liver Disease
• Long-term use of daily colchicine, verapamil at any dose, or diltiazem at a dose >240mg/day.

Key Core Treatment Period:
• Participant was participating in an aducanumab clinical study at the time of the announcement of early termination (feeder studies).
• Has one care partner who, in the Investigator's opinion, has adequate contact with the participant as to be able to provide accurate information about the participant's cognitive and functional abilities. LTE Treatment Period:
• Participant must have completed the Core study period (Week 102) and adequately tolerated 10 mg/kg of aducanumab during the Core study period in the opinion of the Investigator.
• Has one informant/care partner who, in the Investigator's opinion, has frequent and sufficient contact with the participant as to be able to provide accurate information about the participant's cognitive and functional abilities. Key Core Treatment Period:
• Any medical or neurological condition (other than Alzheimer's Disease) that might be a contributing cause of the participant's cognitive impairment.
• Stroke or any unexplained loss of consciousness within 1 year prior to Screening.
• Clinically significant unstable psychiatric illness in past 6 months.
• History of unstable angina, myocardial infarction, advanced chronic heart failure, or clinically significant conduction abnormalities within 1 year prior to Screening.
• A seizure event that occurred after the last visit of the feeder study and before Screening for this study.
• Evidence of impaired liver function as shown by an abnormal liver function profile at Screening.
• History of or known seropositivity for HIV.
• Clinically significant systemic illness or serious infection within 30 days prior to or during Screening.
• Contraindications to having a brain magnetic resonance imaging (MRI). LTE Treatment Period:
• Any medical or psychiatric contraindication or clinically significant abnormality that, in the opinion of the Investigator, will substantially increase the risk associated with the participant's enrollment in and completion of the study. Note- Other protocol defined Inclusion/Exclusion criteria may apply.

1. Age 50 and older 2. Fluent in English 3. Active diagnosis of MCI or dementia 1. Substance use disorder 2. Has metal fragments in head 3. Taking medications that may interact with the HD-tDCS effect (i.e., amphetamines, L-dopa, carbamazepine, sulpiride, pergolide, lorazepam, dextromethorphan, D-cycloserine, flunarizine, or ropinirole)

• Healthy
• Non-obese (body mass index less than 30 kg/m2)
• Body mass greater than or equal to 65 kg
• Subjects who have cardiac, respiratory, neurological and/or metabolic illnesses
• Any known history of renal or hepatic insufficiency/disease
• Pregnancy or breast feeding
• Current smokers, as well as individuals who regularly smoked within the past 3 years
• Positive urine drug screen
• Currently taking pain modifying medication(s)

• Adults age > = 18 years
• HF with left ventricular ejection fraction <= 40% within 3 months of screening who are not on optimal guideline directed medical therapy
• New York Heart Association class II, III, or IV symptoms
• Age < 18
• Systolic blood pressure < 120 mm Hg at enrollment
• Estimated glomerular filtration rate < 30 mL/min/1.73 m2 as measured by the simplified
• MDRD formula
• Serum potassium > 5.0 mEq/L
• Current need for inotropes
• Cardiac index < 2.2 L/min/m2
• History of revascularization within 30 days or plan for revascularization
• History of type 1 diabetes mellitus
• History of allergic reaction or contraindication to a beta-blocker (BB), mineralocorticoid receptor antagonist (MRA), or sodium glucose cotransporter 2 inhibitor (SGLT2i)
• Contraindication to receive any of the components of the polypill
• Pregnancy
• < 12 month expected survival
• Inability to provide written informed consent
• Persistent or permanent atrial fibrillation who may not have optimal MRI imaging
• Extreme obesity (BMI > 45 kg/m2)
• ICD/PAcemaker devices that are incompatible with MRI

Inclusion criteria: Subjects are eligible to participate if they are undergoing TAVR for aortic stenosis at the University of Texas Southwestern Medical Center. 1. The patient cannot or will not provide informed consent. 2. The patient is aged less than 18 years. 3. The patient's pre-procedural hematocrit is less than 25%. 4. The patient has known human immunodeficiency virus infection 5. The patient has known hepatitis C that has not been treated with antiviral medications 6. In the opinion of the principal investigator, the patient will be unlikely to complete long-term follow up for medical or social reasons (this includes transient patients and patients who have no fixed address).

Inclusion Criteria (all CN participants): 1. Participant with or without subjective memory complaints, verified by a study partner, beyond what one would expect for age 2. Normal memory function documented by scoring above education adjusted cutoffs on the Logical Memory II subscale (Delayed Paragraph Recall, Paragraph A only) from the Wechsler Memory Scale -Revised (the maximum score is 25): 1. 9 for 16 or more years of education 2. 5 for 8-15 years of education 3. 3 for 0-7 years of education 3. Mini-Mental State Exam score between 24 and 30 inclusive (Exceptions may be made for participants with less than 8 years of education at the discretion of the Project Director) 4. Clinical Dementia Rating = 0. Memory Box score must be 0 5. Cognitively normal, based on an absence of significant impairment in cognitive functions or activities of daily living 6. Stability of Permitted Medications for at least 4 weeks: 1. Stable doses of antidepressants lacking significant anticholinergic side effects (if they are currently adequately treated for depressive symptoms and do not have a history of major depression within the past 1 years) 2. Estrogen replacement therapy is permissible 3. Gingko biloba is permissible, but discouraged 4. Washout from psychoactive medication (e.g., excluded antidepressants, neuroleptics, chronic anxiolytics or sedative hypnotics, etc.) for at least 4 weeks prior to screening. Inclusion Criteria (all MCI participants): 1. Participant must express a subjective memory concern as reported by participant, or recalled by study partner or clinician. 2. Abnormal memory function documented by scoring below education adjusted cutoffs on the Logical Memory II subscale (Delayed Paragraph Recall, Paragraph A only) from the Wechsler Memory Scale -Revised (the maximum score is 25): a. < 11 for 16 or more years of education b. ≤ 9 for 8-15 years of education c. ≤ 6 for 0-7 years of education 3. Mini-Mental State Exam score between 24 and 30 inclusive (Exceptions may be made for participants with less than 8 years of education at the discretion of the Project Director) 4. Clinical Dementia Rating = 0.5. Memory Box score must be at least 0.5 5. General cognition and functional performance sufficiently preserved such that a diagnosis of Alzheimer's disease cannot be made by the site physician at the time of the Screening Visit 6. Stability of Permitted Medications for at least 4 weeks: 1. Stable doses of antidepressants lacking significant anticholinergic side effects (if they are currently adequately treated for depressive symptoms and do not have a history of major depression within the past 1 years) 2. Cholinesterase inhibitors and memantine are allowable if stable for 12 weeks prior to Screening Visit 3. Estrogen replacement therapy is permissible 4. Gingko biloba is permissible, but discouraged 5. Washout from psychoactive medication (e.g., excluded antidepressants, neuroleptics, chronic anxiolytics or sedative hypnotics, etc.) for at least 4 weeks prior to screening. Inclusion Criteria (all AD participants): 1. Participant must express a subjective memory concern as reported by participant, or recalled by study partner or clinician.n. 2. Abnormal memory function documented by scoring below education adjusted cutoffs on the Logical Memory II subscale (Delayed Paragraph Recall, Paragraph A only) from the Wechsler Memory Scale -Revised (the maximum score is 25): 1. ≤ 8 for 16 or more years of education 2. ≤ 4 for 8-15 years of education 3. ≤ 2 for 0-7 years of education 3. Mini-Mental State Exam score between 20 and 24 inclusive (Exceptions for scores of 24 and 25 may be made for participants with less than 8 years of education at the discretion of the Project Director) 4. Clinical Dementia Rating = 0.5 or 1.0 5. NINCDS (National Institute of Neurological and Communicative Disorders and Stroke) -ADRDA (Alzheimer's Disease and Related Disorders Association) criteria for probable AD 6. Stability of Permitted Medications for at least 4 weeks: 1. Stable doses of antidepressants lacking significant anticholinergic side effects (if they are currently adequately treated for depressive symptoms and do not have a history of major depression within the past 1 years) 2. Cholinesterase inhibitors and memantine are allowable if stable for 12 weeks prior to Screening Visit 3. Estrogen replacement therapy is permissible 4. Gingko biloba is permissible, but discouraged 5. Washout from psychoactive medication (e.g., excluded antidepressants, neuroleptics, chronic anxiolytics or sedative hypnotics, etc.) for at least 4 weeks prior to screening. Inclusion Criteria Specific to Newly Enrolled Participants 1. Geriatric Depression Scale score less than 6. 2. Age between 55-90 years (inclusive). 3. Study partner who has frequent contact with the participant (i.e., minimum average of 10 hours per week) and is available to accompany the participant to all clinic visits for the duration of the protocol. 4. Visual and auditory acuity adequate for neuropsychological testing. 5. Good general health with no diseases expected to interfere with the study. 6. Participant is not pregnant, lactating, or of childbearing potential (i.e. women must be two years post-menopausal or surgically sterile). 7. Willing and able to participate in a longitudinal imaging study. 8. Modified Hachinski Ischemic Score less than or equal to 4. 9. Completed six grades of education or has a good work history (sufficient to exclude mental retardation). 10. Must speak English or Spanish fluently. 11. Willing to undergo repeated MRIs (3Tesla) and at least two PET scans 12. Agrees to collection of blood for genomic analysis (including GWAS (genome-wide association study) sequencing and other analysis), APOE (Apolipoprotein E) testing and biospecimen banking. 13. Agrees to collection of blood for biomarker testing. 14. Agrees to at least one lumbar puncture for the collection of CSF. 15. Agrees to share genomic data and biomarker samples. Inclusion Criteria Specific to Rollover Participants" The following additional inclusion criteria apply to all diagnostic categories for rollover participants only: 1. Must have been enrolled and followed in ADNI-1, ADNI-GO, or ADNI-2 for at least one year. 2. Willing and able to continue to participate in an ongoing longitudinal study. A reduced battery of tests is allowable if the participant is not able/willing to complete the full battery. Exclusion Criteria (all CN participants): 1. Any significant neurologic disease, such as Parkinson's disease, multi-infarct dementia, Huntington's disease, normal pressure hydrocephalus, brain tumor, progressive supranuclear palsy, seizure disorder, subdural hematoma, multiple sclerosis, or history of significant head trauma followed by persistent neurologic deficits or known structural brain abnormalities Exclusion Criteria (all MCI participants): 1. Any significant neurologic disease other than suspected incipient Alzheimer's disease, such as Parkinson's disease, multi-infarct dementia, Huntington's disease, normal pressure hydrocephalus, brain tumor, progressive supranuclear palsy, seizure disorder, subdural hematoma, multiple sclerosis, or history of significant head trauma followed by persistent neurologic deficits or known structural brain abnormalities. Exclusion Criteria (all AD participants): 1. Any significant neurologic disease other than Alzheimer's disease, such as Parkinson's disease, multi-infarct dementia, Huntington's disease, normal pressure hydrocephalus, brain tumor, progressive supranuclear palsy, seizure disorder, subdural hematoma, multiple sclerosis, or history of significant head trauma followed by persistent neurologic deficits or known structural brain abnormalities. Exclusion Criteria (all participants): The following additional exclusion criteria apply to all diagnostic categories: 1. Screening/Baseline MRI brain scan with evidence of infection, infarction, or other focal lesions or multiple lacunes or lacunes in a critical memory structure 2. Subjects that have any contraindications for MRI studies, including the presence of cardiac pacemakers, or metal fragments or foreign objects in the eyes, skin or body. 3. Major depression, bipolar disorder as described in DSM-IV within the past 1 year. Psychotic features, agitation or behavioral problems within the last 3 months that could lead to difficulty complying with the protocol. 4. Currently treated with medication for obsessive-compulsive disorder or attention deficit disorder. 5. History of schizophrenia (DSM IV criteria). 6. History of alcohol or substance abuse or dependence within the past 2 years (DSM IV criteria). 7. Any significant systemic illness or unstable medical condition, which could lead to difficulty complying with the protocol. 8. Clinically significant abnormalities in B12 or thyroid function tests (TFTs) that might interfere with the study. A low B12 is exclusionary, unless follow-up labs (homocysteine (HC) and methylmalonic acid (MMA)) indicate that it is not physiologically significant. 9. Residence in a skilled nursing facility. 10. Current use of specific psychoactive medications (e.g., certain antidepressants, neuroleptics, chronic anxiolytics or sedative hypnotics). Current use of warfarin or other anticoagulants such as dabigatran, rivaroxaban and apixaban (exclusionary for lumbar puncture). 11. Current use of any other exclusionary medications 12. Investigational agents are prohibited one month prior to entry and for the duration of the trial. 13. Participation in clinical studies involving neuropsychological measures being collected more than one time per year. Exclusion Criteria Specific to AV-1451 PET: The following criteria are exclusionary only for the AV-1451 scanning portion of the study: 1. History of risk factors for torsades de pointes (a cardiac dysrhythmia associated with sudden death) or taking medications known to prolong the QT interval. A list of restricted medications will be provided. 2. Have an ECG obtained prior to the AV-1451 PET scan that in the opinion of the investigator is clinically significant with regard to the subject's participation in the study. Bazett's corrected QT (QTcB) interval must be evaluated and must not exceed 458 msec in males, or 474 msec in females.