Developmental effects of environmental enrichment on selective and auditory sustained attention

Abstract

Environmental enrichment (EE) has been used as a positive manipulation in different disease models. However, there is conflicting evidence reported in the literature about the effects of EE. Additionally, the time period that would be most beneficial in implementing environmental enrichment as an intervention is not clear. Our study aimed to systematically compare the prenatal, juvenile, mid-adolescence, and adulthood developmental trajectory to further the understanding of enriched environment's effects on selective and auditory sustained attention, corresponding to behavioral (conceived) and physiological-reflexive (non-conceived) measures. Rats were exposed for 21 days to enriched environment during various developmental periods and compared to age-matched controls. All groups were tested for long-term effects (at postnatal day 120 and onward) on selective and sustained attention. We found that the exposure to enriched environment during mid-adolescence has yielded the most significant and long-term pattern of effects, including selective and auditory sustained attention performance, increased foraging-like behavior and a significant decrease in corticosterone level. Similarly, the exposure to EE at juvenile period improved selective attention, increased foraging-like behavior, and reduced anxiety levels as reflected in the open field as well as in low corticosterone levels. These results specify a crucial period along the developmental trajectory for applying environmental enrichment. Mid-adolescence is suggested, in future basic and translational studies, as the sensitive time period that induces the most beneficial and long-term effects of EE on attention. The current findings suggest that the exposure to EE during mid-adolescence should be further considered and studied as behavioral alternative intervention, or as adjuvant behavioral therapy, aimed to decrease the probability to develop ADHD in post-adolescence period. This suggestion is highly relevant due to the debate regarding the pros and cons of screens usage (e.g. Facebook, online games, etc.) during early life that decreases environmental enrichment, especially, direct social interaction.

Keywords: Anxiety; Auditory sustained attention; Corticosterone; Environmental enrichment; Object recognition; Selective attention.