For a long time it was simply assumed that there was no production of new neurons after birth. More and more evidence shows that this is not the case. Certain areas of the brain, such as the hippocampus (an area critical for memory formation), produce new neurons throughout adulthood. We also know that dendritic branching and synaptic development can occur throughout the lifespan. Neurogenesis (the creation of new neurons) can be bolstered by physical exercise, diet, appropriate levels of rest and relaxation, mental stimulation, and by certain medications, such as antidepressants, that act on the neurotransmitter known as serotonin.