Neuroimaging methods in Aromatherapy research of human studies: a scoping review protocol

Aromatherapy has been increasingly investigated for its potential effects on cognition, emotion, stress, behavior, and clinical outcomes; however, the neurobiological mechanisms underlying these effects remain only partially understood. Several neuroimaging and neurophysiological techniques have been applied to investigate neural responses to aromatherapy, but the methodological landscape of this research remains fragmented and heterogeneous. This scoping review aims to systematically map and characterize the neuroimaging and neurophysiological methods used to investigate the neural effects of aromatherapy in humans and to develop a methodological framework to support the selection and application of these techniques in future research. The review will include primary studies involving human participants that investigate aromatherapy using essential oils administered through interventions involving olfactory exposure, including inhalation and topical application, and that employ at least one neuroimaging or neurophysiological method to assess brain responses or other neurobiological outcomes. Studies using oral or non-olfactory routes, as well as studies evaluating only behavioral, physiological, biochemical, or psychological outcomes without neuroimaging or neurophysiological assessment, will be excluded. The review will follow the Joanna Briggs Institute methodology for scoping reviews and will be reported according to PRISMA-ScR. Searches will be conducted in PubMed/MEDLINE, EMBASE, Web of Science Core Collection, Scopus, CINAHL Complete, PsycINFO, LILACS, and SciELO, without restrictions on publication year or language. Two reviewers will independently conduct study selection and data extraction. Findings will be synthesized descriptively through evidence mapping, summary tables, and graphical representations to characterize methodological approaches, neurobiological outcomes, strengths, limitations, and knowledge gaps, and to identify underexplored neuroimaging approaches established in olfactory neuroscience.