Decreased use of spatial pattern separation in contemporary lifestyles may contribute to hippocampal atrophy and diminish mental health

The spatial pattern separation process has not yet been proposed as a pivotal neural activity affecting hippocampal volume, a metric of mental health. The dentate gyrus/CA3 region is increasingly implicated in hippocampal atrophy, its putative role in spatial pattern separation appears to be impaired in mental health disorders, and performance on a task indicative of pattern separation correlates with dentate gyrus/CA3 volume. Spatial pattern separation is thought to utilize the heightened neural plasticity of newborn neurons in the dentate gyrus to distinguish highly similar aspects of scene so that these remain distinct in memory rather than lost. The level of such activity associates with BDNF secretion, which may affect neuroplasticity and therefore hippocampal volume. Distinguishing fine-grained aspects of surroundings was likely of great importance during hunting and gathering for survival in nature. However the need to make subtle environmental discriminations is much reduced in modern survival activity. Ancestrally, exploration and utilization of the spatial pattern separation process may have resulted in detection of potential food items, an activity that was likely followed by intensive effort-based reward (EBR) activity to obtain the food. EBR activity and restorative walking in nature demonstrate positive mental health benefits, while their lack indicates negative effects on mental health. Data support the hypothesis that spatial pattern separation activity and neural circuitry are separate from, and may precede, those of EBR as well as restorative walking in nature. Spatial pattern separation therefore represents an additional nature-related neural process whose modern decrease in use may negatively affect mental health. Interventions that increase spatial pattern separation experiences may enhance BDNF secretion, neuroplasticity, hippocampal volume and mental health.