Differential effects of social and physical environmental enrichment on brain plasticity, cognition, and ultrasonic communication in rats

Abstract

Environmental enrichment (EE) exerts beneficial effects on brain plasticity, cognition, and anxiety/depression, leading to a brain that can counteract deficits underlying various brain disorders. Because the complexity of the EE commonly used makes it difficult to identify causal aspects, we examined possible factors using a 2 × 2 design with social EE (two vs. six rats) and physical EE (physically enriched vs. nonenriched). For the first time, we demonstrate that social and physical EE have differential effects on brain plasticity, cognition, and ultrasonic communication. Expectedly, physical EE promoted neurogenesis in the dentate gyrus of the hippocampal formation, but not in the subventricular zone, and, as a novel finding, affected microRNA expression levels, with the activity-dependent miR-124 and miR-132 being upregulated. Concomitant improvements in cognition were observed, yet social deficits were seen in the emission of prosocial 50-kHz ultrasonic vocalizations (USV) paralleled by a lack of social approach in response to them, consistent with the intense world syndrome/theory of autism. In contrast, social EE had only minor effects on brain plasticity and cognition, but led to increased prosocial 50-kHz USV emission rates and enhanced social approach behavior. Importantly, social deficits following physical EE were prevented by additional social EE. The finding that social EE has positive whereas physical EE has negative effects on social behavior indicates that preclinical studies focusing on EE as a potential treatment in models for neuropsychiatric disorders characterized by social deficits, such as autism, should include social EE in addition to physical EE, because its lack might worsen social deficits.

Studying Socio‐Affective Communication in Rats through Playback of Ultrasonic Vocalizations

“…Finally, USV emission by the subject rat in response to playback of 50-kHz USVs can be determined (Avisoft Bioacoustics). By this means, it has been consistently shown that 50-kHz USVs lead to social approach behavior in juvenile and adult male rats (Wöhr and Schwarting, 2007, 2009, 2013Brenes et al, 2016;Seffer et al, 2015) as well as in female rats (Willadsen et al, 2014; Fig. 8.35.2), supporting the notion that they serve an affiliative function as social contact calls.…”

“…No social deficits were seen when long-term social isolation was implemented after the rough-and-tumble play period. In the second study (Brenes et al, 2016), the effects of social versus physical environmental enrichment on social approach behavior in response to playback of 50-kHz USVs were compared. While rats housed in groups of two displayed social approach behavior, more prominent approach behavior was seen in rats housed in groups of six.…”

“…In two recent studies, the housing conditions were systematically manipulated and the effects of post-weaning social isolation (Seffer et al, 2015;Fig. 8.35.3) and social versus physical environmental enrichment (Brenes et al, 2016) were investigated. In the first study (Seffer et al, 2015;Fig.…”

The effects of environmental enrichment objects on behaviors ofJapanese quails at different cage stocking densities

“…(Newberry, 1995;Young, 2003). EE exerts beneficial effects on brain, behavior and cognition, for instance by affecting endocrinologic, immunologic, and neuroplastic parameters (Buscherta et al, 2016;Brenes et al, 2016). EE applications are often discussed within the context of welfare of animals hosted in cages (Wolfie, 2005).…”

Extinction of Contextual Fear with Timed Exposure to Enriched Environment: A Differential Effect

“…However, our understanding of the effect of EE on connectivity between brain regions is rudimentary. Studies have shown that EE can influence brain plasticity in the hippocampus [19] , amygdala [20], and prefrontal cortex [21] . However, these studies have failed to provide information about neuronal oscillations which have functional relevance to the behavior of animals.…”