A growing body of empirical evidence from recent psychological research supports the beneficial implications of interacting with the natural world for patients suffering from psychiatric illness (1,2).
It has been repeatedly shown that interacting with nature increases prosocial behavior and with it the sense of social connectedness (3-5), increases pro-environmental behavior and promotes emotional connection towards the natural environment (6,7), as well as Improves cognition and affect in individuals with depression and anxiety (8-14).
However, the biological underpinnings of these observations remain largely unknown.
Oxytocin (OT) is a neuropeptide involved in modulating a wide variety of social behavior in diverse species, ranging from nematodes to humans. In humans, OT is related to high levels of social sensitivity necessary for human sociality, increased facial recognition and emotional sensitivity to facial expressions, and enhanced prosocial behavior (15-18).
Intranasal administration of OT has been shown to increases trust in humans (19,20), modulate social value representations in the amygdala (21), and it is currently prescribed for treating anxiety, depression and social dysfunctions.
Taken together, these observations suggest that the oxytocinergic system has evolved to mediate social inter-dependence behavior.
By their nature, neural systems optimally adapt to represent the environment in which an organism lives (22). As such, behaviorally relevant stimuli such as facial expressions, or tree species native to one’s natural habitat (23-25), are learned and amplified though evolutionary and developmental processes, such as experience-dependent pruning during childhood (26). Accordingly, the representations of such complex natural stimuli are processed in categorically-specialized, high order cortices, with their associated value represented in downstream subcortical regions (27-31).
Since human survival is directly dependent on our relationship with the immediate natural environment, we hypothesize a potential evolutionary link between the natural perceptual category of trees and the oxytocinergic system.
We suggest that activating these functional networks, using a high-resolution video of trees in natural landscapes, similarly to the way natural scenes are used in fMRI experiments, could evoke internal representations of primal valence and their associated emotional representations, potentially balancing the oxytocin levels and naturally inducing prosocial tendency. This approach promotes exposure to nature as a potential treatment for modern psychopathologies rooted in aberrant social functioning such as anxiety, depression, addiction and autism.