What is the current evidence for adult hippocampal neurogenesis?

• A. It is robust in humans and uncontroversial.
• B. Animal studies show ongoing creation of new hippocampal neurons; environmental enrichment enhances this; human evidence is limited but suggestive.
• C. There is evidence for adult hippocampal neurogenesis in animals; in humans it is robust.
• D. Neurogenesis occurs only in the hippocampus of humans, not animals.

Answer: (B)

The main idea here is what current research shows about adult hippocampal neurogenesis. In animals, there is clear and ongoing creation of new neurons in the hippocampus, especially in the dentate gyrus. This process can be increased by environmental factors such as physical exercise and environmental enrichment, showing that adult neurogenesis is not just a developmental phenomenon but can be modulated in adulthood. When we look at humans, the evidence is more limited and debated. Some studies suggest there might be some neurogenesis in adulthood, but the rate appears to be much less robust than in many animals, and findings can depend on age, health, and the methods used to detect new neurons. Taken together, this pattern matches the statement that animal studies show ongoing neurogenesis with enhancement from enrichment, while human evidence is limited but suggestive.