Effect of environmental enrichment on complex olfactory behavioral readouts in male and female mice

Abstract

Brain plasticity is the phenomenon by which the neural circuits rewire due to the impact of various environmental cues and stimuli, which helps in adapting to the environment. From dendritic spine modulations to the birth of new neurons in adults, many processes contribute to the brain’s plasticity. Adult neurogenesis is the phenomenon by which new neurons are differentiated from neural stem cells during adulthood. It is known to happen in the dentate gyrus in the hippocampus and the subventricular zone (SVZ). This study highlights the role of adult neurogenesis in both these regions, as the hippocampus aids in learning and adult-born neurons in the olfactory bulb refine responses to olfactory stimuli. Adult neurogenesis can be modulated by the environment and stress, and both genders show differences in stress resilience. This project aimed to see how such factors would affect adult neurogenesis in mice and thereby their olfactory learning abilities in a complex behavioral task. A go/nogo 10-component mixture task was performed and the learning pace of the animals and the time taken for each group to discriminate between rewarded and non-rewarded odors were compared. The learning is slower and discrimination time is longer when the mice perform a complex 10-component task compared to that when they perform a simple task involving two odors as rewarding and non-rewarding. The number of adult-born neurons was quantified to correlate learning with adult neurogenesis. We found out that there is no gender-dependent variability in learning. No difference between male and female mice has been observed in the adult neurogenesis in OB and DG or cell proliferation in SVZ. With limited number of animals, we didn’t observe significant differences in learning abilities between enriched versus control mice. However, we need to repeat these experiments with more experimental animals to draw firm conclusions.