An Open Positron Emission Tomography Study to Assess the Effects of Varying Mass of AZD4694 on Radioligand Binding Parameters in Healthy Volunteers and Patients With Alzheimer's Disease

Inclusion Criteria: * Body Mass Index between 18 and 30 kg/m2 and weigh at least 50kg and no more than 100 kg. * Mini Mental State Examination score \>28 (healthy volunteers only) * Mini Mental State Examination score 16-28 (Alzheimer's Disease patients only) * Hachinski Ischemic Score =4 (Alzheimer's Disease patients only) * Clinical diagnosis of probable Alzheimer's Disease according to National Institute of Neurology and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association criteria (Alzheimer's Disease patients only) Exclusion Criteria: * Significant Neurological disease or dementia, as defined clinically or by imaging, other than Alzheimer's Disease that may affect cognition or ability to complete the study (Alzheimer's Disease patients only). * Possible, probable or definite vascular dementia in accordance with the National Institute of neurology and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders association criteria (Alzheimer's Disease patients only). * Current major depressive disorder or other major psychiatric disorders according to Diagnostic and Statistical Manual of Mental Disorders, edition 4, American Psychiatric Association 1994 criteria (Alzheimer's disease patients only). * Depression: Cornell Depression Rating \>9 (Alzheimer's disease patients only). * Abnormal vital signs defined as any of the following: Systolic blood pressure \>180 mmHg, Diastolic blood pressure \>90 mmHg, heart rate \<40 or\>85 beats per minute (Alzheimer's disease patients only). * Myocardial infarction or acute coronary syndrome within the last year (Alzheimer's disease patients only). * Had Positron Emission Tomography measurements for scientific purposes within the last 12 months. * History of any clinically significant disease or disorder which, in the opinion of the investigator, may either put the subject at risk because of participation in the study, or influence the results or the subject's ability to participate in the study (healthy volunteers only). * History or presence of gastrointestinal, hepatic or renal disease or any other condition known to interfere with absorption, distribution, metabolism or excretion of drugs (healthy volunteers only). * History of previous (within the last 5 years) or ongoing psychiatric disease/condition including psychosis, affective disorder, anxiety disorder, borderline state and personality disorder according to the criteria in to Diagnostic and Statistical Manual of Mental Disorders, edition 4, American Psychiatric Association 1994, as assessed by the Mini international neuropsychiatric interview (healthy volunteers only). * Any clinically significant illness, medical/surgical procedure or trauma within 4 weeks of the first administration of Investigational Product (healthy volunteers only). * Any clinically significant abnormalities in clinical chemistry, haematology or urinalysis results as judged by the investigator (healthy volunteers only). * Healthy volunteers\<65 years: abnormal vital signs defined as any of the following: Systolic blood pressure \>140 mmHg, Diastolic blood pressure \>90 mmHg, heart rate \<40 or\>85 beats per minute. * Healthy volunteers≥65 years: abnormal vital signs defined as any of the following: Systolic blood pressure \>160 mmHg, Diastolic blood pressure \>90 mmHg, heart rate \<40 or \>85 beats per minute. * Central Nervous system infarct, infection of focal lesions of clinical significance on MRI scans as judged by the investigator.