Introduction; Part I. Approaches to Society within the Brain: 1. A case of rapidly aging society and its dementia population Jeanyung Chey; 2. Social network positions and health status in older adults Yoosik Youm and Junsol Kim; 3. Social brain and how it links social intelligence and well-being Sunhae Sul and Isu Cho; 4. Genomics of cognitive aging in social isolation Sung-Ha Lee and Seyul Kwak; Part II. Society Interacting with Brain, Cognition, and Health in Late Life: 5. Life course approach to cognitive aging and dementia Jeanyung Chey and Seyul Kwak; 6. Enriched social network and brain function Seyul Kwak, Jeanyung Chey, and Yoosik Youm; 7. Psychoneuroimmunology linking social isolation with cognitive aging Sung-Ha Lee; 8. Loneliness and brain health in late life Hairin Kim and Jeanyung Chey; Part III. An Individual's Cognitive Aging with Others: Key Findings, Issues, and Implications: 9. Social relation and cognitive function in older adults Hoyoung Kim; 10. Social network and the brain Yoosik Youm and Junsol Kim; 11. Origins of individual differences in social behavior and social brain Isu Cho and Sunhae Sul; 12. Preventing dementia with social connection Jeanyung Chey, Isu Cho, Hairin Kim, Hoyoung Kim, Seyul Kwak, Sunhae Sul, Sung-Ha Lee, and Yoosik Youm.