All participants in Set A will be asked to take single oral dose of TAK-831 suspension on Day 1. In Set A, each of the participant will receive a maximum of 3 PET scans with [18F]PGM299; 1 at baseline 2 following a single oral dose of TAK-831 on Day 1 and 5. In Set B, each of the participant will receive 2 PET scans with [18F]PGM299 on Day 1 and 5. Set B will be conducted after the confirmation of blockade of [18F]PGM299 binding by TAK-831 in 2 to 4 participants of Set A.