Advanced single-cell and spatial transcriptomics studies have deepened understanding of brain aging and neurodegenerative conditions such as Alzheimer’s disease and Lewy body dementia. Noteworthy discoveries include brain hemisphere asymmetry in tau and amyloid protein deposits and links between air pollution exposure and alpha-synuclein pathology. These molecular insights illuminate disease progression pathways and potential biomarkers critical for developing targeted interventions in neurodegenerative diseases.