The chapter discusses the trends and unresolved issues in the cognitive neuroscience of aging, focusing on the relationship between brain activity and cognitive performance in older adults. It highlights the challenges in interpreting age-related differences in brain activity, such as increased or decreased activity, and explores various hypotheses to explain these differences, including compensation, dedifferentiation, and changes in brain structure and neurotransmitter levels. The chapter also examines the impact of factors like dopamine, APOE genotype, and physical activity on cognitive function and brain activity in older adults. Additionally, it reviews the influence of training on the aging brain, suggesting that short-term behavioral training can reduce age differences in brain activity and improve cognitive performance. Overall, the chapter emphasizes the complexity of understanding age-related changes in cognition and the need for further research to uncover the underlying mechanisms.The chapter discusses the trends and unresolved issues in the cognitive neuroscience of aging, focusing on the relationship between brain activity and cognitive performance in older adults. It highlights the challenges in interpreting age-related differences in brain activity, such as increased or decreased activity, and explores various hypotheses to explain these differences, including compensation, dedifferentiation, and changes in brain structure and neurotransmitter levels. The chapter also examines the impact of factors like dopamine, APOE genotype, and physical activity on cognitive function and brain activity in older adults. Additionally, it reviews the influence of training on the aging brain, suggesting that short-term behavioral training can reduce age differences in brain activity and improve cognitive performance. Overall, the chapter emphasizes the complexity of understanding age-related changes in cognition and the need for further research to uncover the underlying mechanisms.