It was once believed that the adult human brain no longer generated new neurons to replace those that were old or injured, though neuroscientists now know that to be untrue. However, the full implications of this adult neurogenesis are not well understood. A new paper published in Trends in Cognitive Sciences by Maya Opendak and Elizabeth Gould, both of Princeton University, proposes that neurogenesis in the hippocampus aids in the ability to adapt to one’s environment as it changes.
"New neurons may serve as a means to fine-tune the hippocampus to the predicted environment," Opendak said in a press release. "In particular, seeking out rewarding experiences or avoiding stressful experiences may help each individual optimize his or her own brain. However, more naturalistic experimental conditions may be a necessary step toward understanding the adaptive significance of neurons born in the adult brain.”
There has been a great deal of research into the plasticity of the adult brain in recent years, as it has been demonstrated that it can be shaped by a number of things—such as physical activity, reading, and playing video games, among others—but both positive and negative experiences have been shown to significantly affect the hippocampus, altering memory, tendency toward anxiety, and more. All of these factors play into an individual’s perception of the environment.
"Because the past is often the best predictor of the future, a stress-modeled brain may facilitate adaptive responses to life in a stressful environment, whereas a reward-modeled brain may do the same but for life in a low-stress, high-reward environment," Gould added.
When negative experiences outnumber the positive ones, the function of the hippocampus becomes compromised. The ability to cope with changes in the environment diminishes, and anxiety, depression, and other performance-inhibiting disorders take over.
"Such a scenario could represent processes that are engaged under pathological conditions and may be somewhat akin to what humans experience when exposed to repeated traumatic stress,” continued Opendak.
In order to expedite the amount of information taken in every second, the brain has to expedite and take shortcuts in order to minimize the amount of effort used with interpreting the environment. However, neurogenesis is required for making new connections and adapting to changes from those well-entrenched neuronal connections. While the studies performed to date have been under strict laboratory settings, they hope to move forward with real-world case studies in order to better understand how these new connections are integrated into the perception of environment.
"This more realistic setting has revealed individual differences in adult neurogenesis, with more new neurons produced in dominant versus subordinate male rats," Gould concluded. "Taking findings from laboratory animals to the next level by exploring complex social interactions in settings that maximize individual variability, a hallmark of the human experience, is likely to be especially illuminating.”