Sandro Aparecido-Kanzler, Department of Neuroscience, Center of Biological Sciences, Federal University of Santa Catarina (UFSC), Florianopolis, Brazil Francisco J. Cidral-Filho, Experimental Neuroscience Laboratory (LaNEx), University of Southern Santa Catarina (UNISUL), Palhoça, Santa Catarina, Brazil Rui D. Prediger, Department of Neuroscience, Center of Biological Sciences, Federal University of Santa Catarina (UFSC), Florianopolis; Department of Pharmacology, Center of Biological Sciences, Federal University of Santa Catarina (UFSC), Florianopolis. Brazil

This systematic review is dedicated to deepening the study of two phenomena: binaural beats and isochronic tones. Data from the scientific literature suggest the existence of a promising therapeutic potential in neurology and psychophysiology due to their influence on specific frequencies of brain waves and their implications for mental health and homeostasis of brain neurotransmitters. Prolonged audio stimuli in repetitive and synchronized manner may induce changes in brain waves patterns and, consequently, modulating neurophysiological, and behavioral responses. The literature review was conducted using PUBMED, MEDLINE, LILLACS, and SCIENCE DIRECT online platforms using the search words: “audio brain entrainment,” “auditory beat stimulation, ” “binaural beats,” “brainwave entrainment (BWE),” and “isochronic tones.” The search yielded 674 studies, of which 49 were in duplicate, and 592 were out of the scope of this review, and, therefore, were excluded from the study. The remaining studies were analyzed according to the Cochrane Handbook for Systematic Reviews, resulting in 33 randomized, controlled clinical trials that were then evaluated by the Jadad scale. From that, 17 studies obtained a score of three points or more on the Jadad scale. These studies were fully read and critically analyzed. Binaural beats were used in 15 studies (88.25%), whereas isochronic tones were used only in two studies (11.76%). Although most of the studies reviewed here indicated audio BWE effectiveness, some positive outcomes may require further investigation, with more refined and appropriate evaluation tools, better suited for each specific type of intervention and/or therapeutic target. Considering these limitations, the performance of additional studies with more adequate experimental design and data analysis is recommended, particularly focusing on the neurophysiological and behavioral effects of brain wave entrainment on mental states.

Keywords: Audio brain entrainment. Binaural beats. Brainwave entrainment. Isochronic tones.