Figure 2. Factors influencing neurogenesis during aging. (From left to right) Factors and stimuli influencing neurogenesis, their physiological increase (yellow arrows) or decrease (blue arrows) during aging, as well as effects on neurogenesis through, primarily, a change in NSCs proliferation (arrows) or neuronal survival (arrowhead) are indicated. Red ticks indicate factors whose manipulation has been shown to correlate with cognitive function. nd=not determined; na=not applicable.