ABOVE: © lisa clark
In recent years, images and videos taken with state-of-the-art microscopy techniques have shown that new neurons in the dentate gyrus of the hippocampus go through a series of changes as they link up to existing networks in the brain.
 © lisa clark | A neural stem cell divides to generate a new neuron (green). |
 © lisa clark | As the new neuron grows, it rotates from a horizontal to a vertical position and connects to an interneuron (yellow) in a space called the hilus that sits within the curve of the dentate gyrus. The young neuron also starts making connections with well-established dentate gyrus neurons (blue) as well as neurons in the hippocampus (red). |
 © lisa clark | Once connections are formed, mature neurons send signals into the new neuron, and the cell starts firing off more of its own signals. At around four weeks of age, the... |
© lisa clark | A neural stem cell divides to generate a new neuron (green). |
© lisa clark | As the new neuron grows, it rotates from a horizontal to a vertical position and connects to an interneuron (yellow) in a space called the hilus that sits within the curve of the dentate gyrus. The young neuron also starts making connections with well-established dentate gyrus neurons (blue) as well as neurons in the hippocampus (red). |
© lisa clark | Once connections are formed, mature neurons send signals into the new neuron, and the cell starts firing off more of its own signals. At around four weeks of age, the adult-born neuron gets hyperexcited, sending electrical signals much more often than its well-established neuronal neighbors do. |
 © lisa clark | As the new neuron connects with still more neurons, interneurons in the hilus start to send it signals to tamp down its activity. |
How adult-born neurons function in a circuit
Researchers think neurogenesis helps the brain distinguish between two very similar objects or events, a phenomenon called pattern separation. According to one hypothesis, new neurons’ excitability in response to novel objects diminishes the response of established neurons in the dentate gyrus to incoming stimuli, helping to create a separate circuit for the new, but similar, memory.
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