There have been multiple studies performed to understand the birth of new neurons is substantial to memory formation. Specifically, scientists believe that neurogenesis are a component to pattern separation- the ability to distinguish between similar experiences or events based on senses such as smell or a visual landmark.
Now, scientists are able to produce deficits in pattern separation in animals by blocking neurogenesis using x-ray radiation to kill certain population of cells in the brain where the dentate granule neurons are located. However, this technique does not pinpoint which actual cells of which are being recorded from.
A new study with mice explains how newly born neurons and mature dentate granule neurons differ in activity. Researchers at Columbia University used mice that have been genetically engineered to convey fluorescent molecules of neurons up to 6 weeks old. Scientists blocked the newly born neurons with the technique of optogenetics- a tool used to pretty much turn a cell on and off like the switch of a light. When scientists performed this technique, the mice were not able to distinguish which between 2 different chambers; one where they were mildy zapped on their leg and the other where no zapping occurred. The experimental mice expressed distress when placed in either chambers, whereas the control group only expressed it within the chamber they were shocked- which supports the idea that neurogenesis corresponds to pattern separation.
Another study was conducted when the mice were placed on a treadmill and given specific stimuli as running through different environments with the use of different sounds, visual clues, and scents. After examining the activity in the mices' brains, the researchers observed that mature cells' firing were fine tuned into a specific location, whereas the locations of the young cells firing were arbitrary, in which presumes that as they mature the cells will develop a more designated firing location. It's not surprising that the mature cells had specific firing locations, for it corresponds to the model of neurogenesis and memory formation. The task for the young neurons isn't so much to carry new information about spatial location and environmental context in certain occurrences, but moreso temper the activity the older cells responding to that information.
Research is now suggesting that deficits in pattern separation- likely in people with anxiety, depression, and PTSD may undergo difficulty in distinguishing between past fearful and sad events and novel experiences. Other evidence suggests that treatments such as antidepressants and exercise can help people with these conditions to maintain a better separation between the past and the present.