Enrichment of Neurogenesis in the Hippocampus via the Environment

Lay Summary

Can memory improve by exploring stimulating environments in reality and in 3-D video games?

Intriguing research in young adults suggests that their memory can be improved by the act of exploring richly stimulating environments in 3-D video games. Importantly, the memory improvements seen so far are not confined to simply playing the same 3-D video games more effectively with practice. Rather, the improvements appear to transfer to independent memory tasks, suggesting that their memory functions overall are better.

The research has been so promising, in fact, that the investigators now plan to get preliminary evidence on whether older adults derive the same memory benefits from engaging in these 3-D games, in which players navigate their way through richly stimulating environments. Additionally, they will see whether the same memory benefits accrue to older adults navigating in enriched real-world environments, by participating in scavenger hunts in the park.

The research is based on several findings from memory research. For instance, we know that the brain’s hippocampus, which is essential for making and storing memories, continues to produce new neurons throughout life in a part of the hippocampus called the “dentate gyrus.” With advancing age, though, the number of new neurons produced decreases. Those that are produced are less likely to differentiate into specialized brain cells, and more likely to die. This impaired process probably contributes to the memory deficits common in older people and animals.

Yet research also has shown that rodents exploring rich environments produce new neurons and synapses (junctions used by brain cells to communicate with one another) in the hippocampus. Moreover, these changes are thought to help the hippocampus encode the experience as a whole, suggesting that neurons integrate into neural networks by virtue of the learning experience. This process may strengthen memory.

Since we now also know that the brain’s hippocampus has its own GPS, composed of “grid cells” that are active while a person navigates a virtual as well as a real-world environment, it appears that hippocampal navigation likely operates similarly in both environments. So, based on all these factors, the investigators sought to determine whether young adults playing 3-D video games that focused on navigating through interesting environments performed better on general memory tests compared to those who played 2-D video games and those who played no video games at all.

They did. The 3-D video gamers performed better on two types of memory tests that are specific to assessing hippocampal function. One of these tests (called MST) is highly sensitive to hippocampal damage, aging, and to aged-related changes in both the activity of dentate gyrus (which produces new neurons) and to mild cognitive impairment (MCI). The other test is specific to spatial memory performance.

Now, the investigators will extend their research to healthy adults between the ages of 65-75, where memory performance and development of new neurons is already in decline. They will enroll 90 adults into three groups of 30 participating in either: 3-D video training, 2-D video training, or real-world navigation in scavenger hunts in the park. They will see whether environmental enrichment through 3-D video games and/or a real-world exploration experience can improve and ameliorate cognitive deficits in the hippocampus that are already present in the older population, and gain a preliminary indication of whether the cognitive improvements are associated with demonstrable changes in the volume, shape, or connectivity of the hippocampus. One reason for extending the study to scavenger hunting in the park is to address the issue that controlled 3-D video environments are less rich than exploring real-world settings; another reason is that the physical activity of scavenger hunting also may play a role in the effects.

Prior to participating in the video games or scavenger hunt, all participants will take tests assessing their memory, attention, and executive function, and undergo MRI imaging of the brain’s hippocampus and MRI-DTI imaging of “white matter” (connections between brain regions). These tests and imaging will then be repeated after participants undergo four weeks of video-game practice or scavenger hunts.

The investigators predict an improvement in the generalized memory testing in those participating in 3-D video gaming and in those participating in the real-world scavenger navigation game. They also anticipate that adults in these two groups will show changes in neural connections and volume (a proxy for increased numbers of neurons) in the hippocampus.

If this preliminary study suggests that environment-rich navigation training in older adults shows a generalized effect on memory improvement, the study will lead to expanded research on whether the training has an effect on the generation of new neurons in the dentate gyrus and how this neuroplasticity is associated with networks in the hippocampus that are involved in memory.

Significance: This study will provide preliminary evidence of whether training to navigate stimulating environments has an effect on improving memory in older people by aiding the production of new neurons and their integration into networks involved in memory.