Introduction
In modern neuroscience there are several areas of sleep disorders; including physiotherapy, including of noninvasive brain stimulation (non-invasive brain stimulation). In the review (Gorgoni et al. 2013), proves the importance of development of physiotherapeutic methods of treatment of neurological diseases, including sleep disorders, as an alternative drug therapy.
The greatest attention is paid, of course, the deeper stages (slow-wave) sleep, in connection with its proven importance for the implementation of the restorative functions of the body. A substantial part of scientific research, until recently, was devoted to the so-called "contact" physiotherapeutic methods, e.g., transcranial electric stimulation. Most consistently such work is conducted in laboratories, led by Professor Jan Born (Germany) and Giulio Tononi (USA), who investigated the influence of different types of magnetic and electrical stimulation of the brain of people during Delta sleep in the processes of learning and memory. In Russia also developed and patented original technology of the peripheral subthreshold electrical stimulation of the hand during the period of non-REM sleep is implemented in the form of industrial prototypes of the respective devices (Indursky and others 2013). The authors have shown that the use of these devices deepens and prolong the stage of non-REM sleep, improving, including, the condition of subjects with reduced emotional tone.
However, there are known limitations described above physiotherapy methods.
First, contact non-invasive methods are not always suitable for creating devices designed for mass use. In addition, their safety with long-term use is still controversial. Therefore, it also explores the possibility of correction of the sleep process with distant stimuli. Particularly effective in this regard showed acoustic stimulation that the hypothesis (Tononi et. al., 2014) related to the ability of subliminal audio stimuli to synchronize cortical activity of large neuronal populations through activation selenitovyj ways.
Secondly, deep sleep cannot be viewed separately from the process of falling asleep, because if you have problems falling asleep, attempt to impact on further process lose their meaning. Therefore, it is not less important is the parallel development of means of non-pharmacological exposure and the stage of falling asleep.
Given these two observations, asked a direction of this work, namely: a search for advanced acoustic means: a) to accelerate the process of falling asleep; b) to make more predictable the time of falling asleep, that is, the period through which it becomes effective use of already developed means of influence on non-REM sleep.
Publications related to the use of instrumental methods of influence it is on the process of sleep, not enough. This is due to the complexity of such studies, due to the large variability sonographically parameters in different subjects at sleep (J. A. Hobson, 2001; Santamaria J.,1987; Hori T., 1985).
A meta-analysis of studies using sound to facilitate the process of falling asleep showed a clear effectiveness of music for this purpose (G. De Niet et al., 2009). However, setting the correct physiological studies using music complex, as noted in the above review (De Niet G. et al., 2009).
Sound effects are also used in various devices light and sound stimulation (Tang et al., 2015), some software (
http://www.transparentcorp.com/products/np/) and devices of a biological feedback, and recordings of psychotherapeutic orientation. As one of the types of sound effects in them, including applied monaural and binaural beats. Despite the presence of some encouraging publications (Abeln et al., 2014) and a well-deserved popularity of the above-mentioned products among the practitioners, the effect of sound beats for sleep are still largely unexplored in scientific terms. Although the results of our preliminary studies (Dorokhov, Noise, etc., 2001), technology, for example, the binaural beat has a great potential for non-invasive sleep therapy.
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Here it is necessary to clarify the nature and differences of the terms "binaural" and "monaural" beats.
So, according to (G. Oster, 1973), if at the same time slack to bring two tuning forks of slightly different frequencies, the loudness of the sound resultimage periodically increases and decreases. Such modulation is called a monaural beat; the frequency of beats is equal to the difference frequencies of the original tones. For example, the tuning fork frequencies of 440 Hz (the note of the first octave), excited simultaneously with the tuning fork frequencies of 434 Hz, produces beats of frequency 6 Hz. In modern studies, the tuning forks are replaced by electronic oscillators. In this case, the beating happens when the electrical signals from the outputs of the two generators are mixed and fall into a sound source (speaker). But these same signals can be simultaneously submit to two different dynamics and also hear the beats. Therefore, place of mixing signals in the phase of electrical oscillations or acoustic – does not affect the final result.
It is quite a different phenomenon is observed in the case of using the stereo headphones and the signals separately to each ear. In this case, if one ear is hearing a tone with a frequency of 440 Hz and another tone with a frequency of 434 Hz, under certain conditions also appear aural the beats with a difference frequency of 6 Hz, which has, however, a largely subjective nature. These are called binaural beats. They were discovered in 1839 by a German experimenter, G. V., Dofe, but until 1915 it was considered a special case of the normal, monaural, beats that can be heard in one ear (G. Oster, 1973).
Binaural beats are usually seen in the range of 2 to 30 Hz (Perrott and Nelson, 1969) . At a smaller frequency difference between channels, there is simply a change in spatial localization of sound (the stereo field), at most – each ear hears a separate tone. With regard to the carrier frequency (tones, against which the felt heartbeat), it is optimal for perception is considered to range from 200 to 900 Hz (Wahbeh et al., 2007; Pratt et al., 2010).
That is the subjective nature of binaural beats is by design, at the same time as generating interest in their use and the difficulties in scientific research.
As to the first, is that commercial products that use binaural beats, have a strong demand on the market of modern technological tools for relaxation. This is partly the result of marketing, not always adequately referencing scientific data, but more than a million references issued by, for example, the search engine google for this query, - a very eloquent testimony (
http://www.google.com search on 30 Jan 2015). In addition, efforts by some representatives of media business have formed a common opinion about the possibility of the use of binaural beats to achieve the so-called "altered States of consciousness" (F. H. Atwater, 1997), which not only contributed to the commercial success of such technologies, but also had some "side effects", like the "audioerotica" (NADEZHDIN, A. V. et al., 2013).
As for the second remark, or difficulties in study, the main one is, obviously, the instrument check the physiological changes caused by binaural beats. They cause a physiological response is woefully weak (Schwarz D. W. F. and others, 2005, Goodin, J., and others 2012), so there are naturally disagreements about the effectiveness of the use of this technology. In addition, results from different studies is sometimes contradictory, although in General, interest in the topic in the scientific environment is maintained, including in recent years.
So, a number of studies indicates the positive effect of listening to binaural beats on the behavior and cognitive processes. For example, the indicators of attention (Lane et al., 1998) and memory (Kennerly, 1996), the level of hypnotic susceptibility (Brady and Stevens, 2000). There are also data reduction in subjective feelings of anxiety (Le Scouarnec et al., 2001; Padmanabhan et al., 2005) and ringing in the ears (David et al., 2010); the improvement of the indices of cardiac activity (Palaniappan R., 2015). But there is evidence to the contrary: (Stevens et al.,2003) did not find an influence of binaural beats on the hypnotic susceptibility, also not marked changes under the influence of their blood pressure and heart rate (Carter,2008) or decrease caused by the hyperactivity symptoms of attention deficit disorder (Kennel et al., 2010).
The theoretical basis describing the influence of binaural beats on human and largely determines the direction of scientific research is the hypothesis of frequency-guided response (CWA, brainwave entrainment) in the brain in response to resonance effect of the monotonous stimulus, in this case – the beating of constant frequency (see review Vernon D. And others 2014). This hypothesis has not received clear confirmation in force, at least, of the weakness of CVA from binaural beats, however, based on it, we can assume that the stimulation with binaural beats at the frequency of Delta - and theta-rhythm should speed up the process of falling asleep due to pump power fluctuations in the brain in this area from other bands of the EEG, i.e. to advance at least 1 stage of sleep. This assumption is confirmed by preliminary publications (Rhodes, L. 1993, Wilson, E. S. 1990). In addition, there is work (V. Abeln et al., 2014) showing a positive effect of binaural beats on sleep and performance after awakening from a professional sportsmenov. There is also a publication (Tang, H-Y. J., 2015) about the positive effects on people suffering from insomnia, audiovisual stimulation with the same hypothetical mechanism of action.