The aim of the study was to investigate whether visual stimuli have the same potency to increase electroencephalography (EEG) delta wave power density during non-rapid eye movement (NREM) sleep as do auditory stimuli that may be practical in the treatment of some sleep disturbances. Nine healthy subjects underwent two polysomnography sessions—adaptation and experimental—with EEG electrodes positioned at Fz–Cz. Individually adjusted auditory (pink noise) and visual (light-emitting diode (LED) red light) paired 50-ms signals were automatically presented via headphones/eye mask during NREM sleep, shortly (0.75–0.90 s) after the EEG wave descended below a preset amplitude threshold (closed-loop in-phase stimulation). The alternately repeated 30-s epochs with stimuli of a given modality (light, sound, or light and sound simultaneously) were preceded and followed by 30-s epochs without stimulation. The number of artifact-free 1.5-min cycles taken in the analysis was such that the cycles with stimuli of different modalities were matched by number of stimuli presented. Acoustic stimuli caused an increase (p < 0.01) of EEG power density in the frequency band 0.5–3.0 Hz (slow waves); the values reverted to baseline at post-stimuli epochs. Light stimuli did not influence EEG slow wave power density (p > 0.01) and did not add to the acoustic stimuli effects. Thus, dim red light presented in a closed-loop in-phase fashion did not influence EEG power density during nocturnal sleep.

Background Standard treatments for mental, cognitive and psychosomatic disorders do not work for everyone or have undesirable side effects. In fact, there are few or no satisfying solutions for up to 35% of patients. Brainwave entrainment (BWE) has the potential to safely and effectively fill this gap. The term brainwave entrainment refers to the use of rhythmic stimuli with the intention of producing a frequency-following response of brainwaves to match the frequency of the stimuli. The stimulus is usually either visual (flashing lights) or auditory (pulsating tones) or tactile (vibrating subwoofers) on a reclining chair. By those in the industry, it is also commonly called “brain entrainment,” “audiovisual entrainment (AVE),” “audio-visual-tactile entrainment (AVTE),” “audiovisual stimulation (AVS),” “auditory entrainment,” or “photic stimulation.” Preliminary evidence suggests that BWE is effective in several cognitive domains and can relieve acute and long-term stress, reduce pain, headaches, migraines, and PMS and improve behavior [Huang, Charyton, 2008; Thut et al., 2011; see also Basar, 2008]. The AVTE is also reported as effective method with relaxing effect used for neurotechnological correction of psychosomatic disorders, (Stebliuk, 2012, Morse, 1993). It is wll known that AVTE influence sleep, anxiety, neurological disorders (Le Scournec, 2001; Thayer, 2012). In a previous an 8-week study of 28 hypertensives (under drug therapy) the audiovisual entrainment (AVE) in the sub-delta frequency (0.5–1 Hz) and alpha frequency ranges had marked effects on blood pressure, reducing the systolic 20 points and diastolic 15 points. It was also demonstrated that AVE in the low alpha range produced a strong normalizing affect autonomic activity and rate variability (Siever, Berg, 2002). Accordingto our previous investigation the add-on AVTE therapy pharmacotherapy of hypertension led to significantly more efficient correction of abnormal day and night arterial blood pressure (BP) dynamics accompanied by a two-fold reduction of enalapril or propranolol intake in children and teenagers (Aftanas et al., 2013). In view of above, today the AVTE therapy seems to be a safe and promising option as an add-on therapy to pharmacological treatment in uncontrolled hypertension. The goal of this research was to study the effects of the AVTE stimulation course on blood pressure regulation in adult patients with pharmacologically uncontrolled essential hypertension in a randomized, single-blind, placebo-controlled, parallel-group study. Methods Twenty eight in-patients of the A1 Clinic of Novosibirsk’s Scientific Research Institute of Physiology & Basic Medicine” (M±m, M=51,56±1,4 years, 8 men and 15 women) with uncontrolled essential hypertension (1st- and 2nd stages, 10th International Classification of Diseases) were recruited into this study. Patients with a history of significant atrial or ventricular arrhythmia, pacemaker implantation, significant valvular heart disease, primary kidney disease, diabetes mellitus, metabolic syndrome, pregnancy were excluded from the study. The study was approved by the Local Ethics Committee of Clinical Research and the written informed consent was obtained from all of the patients before the study. Ambulatory blood pressure monitoring (ABPM) were made before and after of the treatment course. The measurements were taken with an oscillometric monitor (Spacelabs Healthcare", model 90217А) every 15 min to record the systolic BP, diastolic BP and heart rate in the day interval and 30 min in the night interval continuously over a 24-h period. Patients were instructed to follow their normal routines of daily life, to immobilize their arms during cuff inflation and to record their daytime activities in the diary. Wake and sleep times were determined using a physiological actigraph monitoring. Uncontrolled hypertension was defined according to current ABPM thresholds approved of the European Society of Hypertension and of the European Society of Cardiology (Mancia et al., 2007), specifically awake systolic (SBP)/diastolic (DBP) BP means ≥135/85 mm Hg and/or asleep SBP/DBP means ≥120/70 mm Hg. Sleep-time relative BP decline was defined as percent decline in mean BP during nighttime sleep relative to mean BP during daytime activity. The patients were randomly assigned to either an actively treated (rhythmic stimulation pattern, n = 14) or a sham-stimulation (random stimulation pattern, n=9) group using an automated stratified procedure. The AVTE stimulation course was designed for 7 days with two 30 min morning and afternoon sessions per day yielding 14 overall. Eah session consisted of a rhythmic AVTE, based on the synchronous application of flashings LEDs, binaural beats and vibrations, delivered over dorsal surfices od the thorax and legs via two subwoofers in the varying frequency EEG ranges (i.e., 1.5 - 20 Hz), individually adjusted to the individual alpha peak frequency (APF). For each patient the individual APF was determined immediately before the study [Bazanova, Aftanas, 2010]. Sham AVTE stimulation course was delivered according to the same schedule with the same stimulation parameters. Results Out of 28 intended-to-treat patients, only 23 completed the study. Five patients from the sham-treated group did not finish the study because of reasons unrelated to the study. Within-group repeated measures ANOVAs evidenced that over 14 sessions active stimulation decreased night blood pressure [F (1,13) =6,9, p = 0.02] whereas sham stimulation did not (p>0.05). The active stimulation group manifested significant decrease of 7 points (122 – 115 mm.Hg) in systolic night blood pressure [F(1,13)=6,9, p = 0.02] and a four point (74,5 – 70,5 mm. Hg) decrease in diastolic night blood pressure [F(1,13)=4,7, p=0,04]. The sleep time relative SBP decline significantly went up from 7,69% to 12,4% [F (1,13) = 5,08, p=0,04] in the active...