Scientists have created a detailed map of genetic activity in the **prefrontal cortex**, a part of the brain essential for decision-making, emotional control, planning, and adapting behavior. This map has improved understanding of how the brain develops normally and how it is affected by serious conditions like **Alzheimer's disease**, **Parkinson's disease**, and **schizophrenia**. In total, nine studies looked at how different types of brain cells change with age, aiming to uncover the molecular processes behind these disorders. The brain tissue samples were taken from 1,494 donors, ranging in age from early childhood to 108 years. Multiple studies have found that this brain region is often affected in various neurodegenerative and psychiatric conditions. Dr. Panos Roussos, director of the Center for Neurogenomics of Diseases at the Icahn School of Medicine at Mount Sinai in New York, said that these studies help explain where disease-related changes happen and which biological processes need more attention. He noted that for a treatment to be effective, it must target the correct biological process in the right type of cell. This mapping allows researchers to identify vulnerable cell populations, discover processes that support brain function, and find potential targets for new treatments. Through the research, scientists found that genetic activity related to the development of nerve cells overlaps in specific ways. By comparing brain tissues from donors of different ages, researchers identified molecular changes that occur from early development through to adulthood. The data suggest that around the age of 24, a transition phase occurs after which most cell populations in this brain region stabilize. Dr. Roussos emphasized that this does not mean the brain suddenly finishes developing at 24 or that decline begins at that age. Other parts of brain biology continue to change throughout a person's life. The team also identified specific cellular patterns linked to differences in cognitive abilities and depression seen in **Alzheimer's disease**. Researchers have connected hereditary genetic risks for diseases with specific genes and cell types, mapping the genetic influences on the activity of more than 14,000 genes. Dr. Roussos suggested that this indicates aging may alter the daily biological rhythms in the brain. Whether restoring these rhythms could improve brain health remains an important question for future research.