This study uses imaging to evaluate how LY3372689 binds to a protein in the brain. This study will be conducted in healthy participants and will last up to about 10 weeks. Screening must be completed within four weeks prior to enrollment.

Inclusion Criteria:

• Overtly healthy males or females who do not have child-bearing potential
• Have a body mass index (BMI) of greater than (>)18 to less than or equal to (≤32) kilograms per square meter (kg/m²), inclusive, at screening
• Have normal blood pressure, pulse rate, electrocardiogram (ECG, heart tracing), blood and urine laboratory test results that are acceptable for the study
• Have venous access sufficient to allow for blood sampling

Exclusion Criteria:

• Have a history of head injury or contraindications to undergoing magnetic resonance imaging (MRI) examination
• Are currently participating in or completed a clinical trial within the last 30 days or any other type of medical research judged to be incompatible with this study
• Have previously participated or withdrawn from this study
• Have had prior participation in other research protocols or clinical care in the preceding year in addition to the radiation exposure expected from participation in this clinical study, such that radiation exposure exceeds the effective dose of 50 milliSievert (mSv), which would be above the acceptable annual limit established by the US Federal Guidelines
• Are current smokers or have used tobacco or nicotine-containing products as determined by the cotinine test
• Have or used to have health problems or laboratory test results or ECG readings that, in the opinion of the doctor, could make it unsafe to participate or could interfere with understanding the results of the study
• Participate in regular vigorous exercise