Department of Psychology, University of Duisburg-Essen, Essen, Germany.
PLoS One. 2023 May 19;18(5):e0286023. doi: 10.1371/journal.pone.0286023. eCollection 2023.
Binaural beats are an auditory phenomenon that occurs when two tones of different frequencies, which are presented separately to each ear, elicit the sensation of a third tone oscillating at the difference frequency of the two tones. Binaural beats can be perceived in the frequency range of about 1-30 Hz, a range that coincides with the main human EEG frequency bands. The brainwave entrainment hypothesis, which assumes that external stimulation at a certain frequency leads to the brain's electrocortical activity oscillating at the same frequency, provides the basis for research on the effects of binaural beat stimulation on cognitive and affective states. Studies, particularly in more applied fields, usually refer to neuroscientific research demonstrating that binaural beats elicit systematic changes in EEG parameters. At first glance, however, the available literature on brainwave entrainment effects due to binaural beat stimulation appears to be inconclusive at best. The aim of the present systematic review is, thus, to synthesize existing empirical research. A sample of fourteen published studies met our criteria for inclusion. The results corroborate the impression of an overall inconsistency of empirical outcomes, with five studies reporting results in line with the brainwave entrainment hypothesis, eight studies reporting contradictory, and one mixed results. What is to be noticed is that the fourteen studies included in this review were very heterogeneous regarding the implementation of the binaural beats, the experimental designs, and the EEG parameters and analyses. The methodological heterogeneity in this field of study ultimately limits the comparability of research outcomes. The results of the present systematic review emphasize the need for standardization in study approaches so as to allow for reliable insight into brainwave entrainment effects in the future.
双耳节拍是一种听觉现象，当两个不同频率的音调分别呈现给每只耳朵时，会产生第三个音调以两个音调的差频振荡的感觉。双耳节拍可在约 1-30 Hz 的频率范围内感知，该频率范围与主要的人类 EEG 频带相吻合。脑波同步假说假设外部刺激在某个频率下会导致大脑的皮层电活动以相同的频率振荡，为研究双耳节拍刺激对认知和情感状态的影响提供了依据。研究，特别是在更应用的领域，通常参考神经科学研究，证明双耳节拍会引起 EEG 参数的系统变化。然而，乍一看，关于双耳节拍刺激引起的脑波同步效应的可用文献似乎最多也只是不确定的。因此，本系统综述的目的是综合现有的实证研究。符合纳入标准的十四项已发表研究被纳入样本。结果证实了实证结果总体不一致的印象，五项研究的结果与脑波同步假说一致，八项研究的结果与假说相悖，一项研究的结果则混合。值得注意的是，本综述中纳入的十四项研究在双耳节拍的实施、实验设计以及 EEG 参数和分析方面非常多样化。该研究领域的方法学多样性最终限制了研究结果的可比性。本系统综述的结果强调了在研究方法上标准化的必要性，以便将来能够对脑波同步效应有可靠的了解。
