Auditory nerve fibers leaving the cochlea converge with the vestibulocochlear nerve and enter the cochlear nucleus (CN) in the brainstem and bifurcate.
Auditory information is further processed at a number of subcortical structures. This is the first order of auditory processing prior to sound waves being encoded (or rather re-encoded) by the primary auditory cortex. Neurophysiology of Auditory Beat ProcessingĪcoustic stimuli are heard when the peripheral components of the auditory pathway (ears, cochlea, and inner hair cells) convert pressure waves into neural action potentials via mechano-electrical transduction. This indicates that beat carrier frequencies have to be sufficiently low enough to be temporally encoded by the cortex ( 9). Oster reported that the binaural beats were detected only when the carrier frequency was below 1000 Hz, a finding that confirmed an earlier study by Licklider and colleagues ( 8). Dove in 1839 and outlined in detail by Oster over five decades ago ( 7). The binaural beat percept was first reported by H. For example, when the 400 Hz tone is presented to the left ear and the 440 Hz tone to the right, a beat of 40 Hz is perceived, which appears subjectively to be located “inside” the head. Binaural beats are generated when the sine waves within a close range are presented to each ear separately. The beat corresponds to the difference between the two frequencies (in this case 40 Hz). Monaural beats are physical beats, which are objectively heard when the combination of two sine waves at neighboring frequencies (e.g., 400 and 440 Hz) are summated and presented to each ear at the same time resulting in an amplitude modulated (AM) signal. Monaural and binaural beats are generated when sine waves of neighboring frequencies and with stable amplitudes are presented to either both ears simultaneously (monaural beats) or to each ear separately (binaural beats). The main differences between binaural and monaural beats are listed in Table Table1. The effects of ABS have been predominantly investigated using monaural and binaural beats (Figure (Figure1). During the construction of the manuscript, several other references were added, mainly referring to basic neurophysiological findings. After screening, a total of 30 articles were selected.
BINAURAL AUDIO MEDITATION FULL
Abstracts were screened for relevance and then full texts were assessed against inclusion criteria. Exclusion criteria were other study designs (case reports and case series), non-original studies including editorials, book reviews, and letters to the editor, and studies not specifically designed and focused on monaural and/or binaural-beat stimulation. Manuscripts in English, original articles, and experimental studies were considered. Articles that presented a combination of at least two terms from the list of search terms, “auditory beat stimulation, monaural beat, binaural beat, cognition, memory, attention, mood, vigilance, anxiety and creativity” were included. Analysis of the papers followed the inclusion and exclusion criteria recommended by the PRISMA Guidelines. A total of 920 articles were identified in the initial search. In addition to the electronic search strategy, the reference lists of the manuscripts that were reviewed were examined to identify any additional articles not captured by the main search strategy. The electronic databases PubMed and MEDLINE were searched initially using the single search terms “auditory beat stimulation, monaural beat, binaural beat, auditory steady-state response,” and then the combination of these search terms with the terms “cognition, memory, attention, mood, vigilance, anxiety, and creativity.” The strategy was not limited to human studies. This review was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria ( 6).
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