The neural and physiological mechanisms of animal assisted interventions (AAI)

Background: Animal-Assisted Interventions (AAIs) have demonstrated therapeutic benefits across diverse clinical populations and settings. However, the underlying neurological and physiological mechanisms that produce these effects remain poorly understood. While previous research has examined physiological responses to human-animal interactions, there is limited integration of central nervous system processes with peripheral biomarkers, and most studies have focused predominantly on dog-assisted interventions. Objectives: This systematic review aims to synthesize evidence on both neural and physiological mechanisms underlying AAI effects. Specifically, we will integrate findings from neuroimaging studies (fMRI, EEG, NIRS) with physiological biomarker research (cortisol, oxytocin, heart rate, blood pressure) to develop a comprehensive theoretical framework. The review will examine interactions with diverse animal species across various clinical populations. Methods: Following PRISMA guidelines, we will systematically search ProQuest, PubMed, PsycINFO, and Scopus databases using three concept groups: animal intervention terms, neurological measurement terms, and physiological measurement terms. This review reports the results of a search conducted through March 2025. Inclusion criteria require peer-reviewed empirical studies in English that measure neurological or physiological outcomes from structured AAIs involving live animals. Studies using non-live animals, unstructured exposure, or non-empirical designs will be excluded. Data extraction will document measurement techniques, animal species, population characteristics, intervention parameters, and study outcomes.Expected Contributions: This review will provide the first comprehensive integration of central and peripheral biological mechanisms in AAI research, establish a theoretical framework connecting neural changes to physiological outcomes, identify promising mechanisms warranting further investigation, and inform evidence-based practice by clarifying how and why AAIs may be effective for specific populations and conditions. Keywords: Animal-assisted interventions, neuroscience, physiological mechanisms, stress, emotion regulation, oxytocin and cortisol