Another theory about how new cells become incorporated into the existing neuronal networks and participate in processes of learning suggests that the new cells are used to replace existing mature cells in the dentate gyrus [86].
The presence of new neurons in the adult hippocampus indicates that this structure incorporates new neurons into its circuitry and uses them for some function related to learning and/or related thought processes. Their generation depends on a variety of factors ranging from age to aerobic exercise to sexual behavior to alcohol consumption.
Neurogenesis and the spacing effect: learning over time enhances memory and the survival of new neurons. Learning & Memory. 2007;14:368–75. [PMC free article][PubMed] [Google Scholar]
To unleash the full potential of neural networks, we can use the the output of one neuron as the input of other neurons, whose outputs can be the input to yet other neurons, and so on. The output of the whole network is obtained as the output of a certain subset of the neurons, which are called the output layer.