Sleep disorders are increasing in their incidence and prevalence in the general population and pose enormous public health issues. An effective therapy for the most common sleep disorders could bring massive public health benefits in terms of physical health, psychological well-being, and productivity. Indeed, sleep disorders have been strongly associated with depression and anxiety.
The normal sleep cycle is divided into two main phases each embodying characteristic physiological constellations.
Sleep centers in the nervous system regulate the rhythm of circadian sleep/wake cycles. The suprachiasmatic (SNC) nucleus of the anterior hypothalamus receives impulses from retinal nerves and other special senses. The SNC projects nerve fibers into the hypothalamus which, in turn, has influence over locomotor activity, food and water intake, body temperature, and hormone levels. It is apparent, therefore, that sleep functions actively weave into the spectrum of basic bodily functions.
In one of these phases, a salient feature is the emergence of rapid eye movement (REM). This phase is called REM sleep. In the other phase, eye movements are relatively absent. This phase is called non-REM, or NREM sleep. During the course of the night, there are several periods of alternating REM and NREM sleep phases.
REM periods are associated with, in addition to eye motions, EEG rhythms found in the waking state such as alpha waves (8 to 12 cycles per second), the inhibition of muscle activity, the engagement of the autonomic nervous system as expressed in blood pressure and heart rate fluctuations, and with dreaming. 20% to 25% of sleep time is devoted to REM sleep. In normal sleep, an initial NREM phase of approximately 70 to 100 minutes duration is followed by the first REM period. Depending upon total sleep time, this cycle is repeated 4 to 6 times during the night.
NREM cycles do not show the characteristic horizontal and vertical eye motions found in REM sleep. In the beginning of the nightly sleep cycle, alpha waves begin to give way to low-voltage, theta, 4 to 7 cycles per second brain waves. This is identified as stage 1 sleep.
Stage 2 sleep usually occurs less than a minute later, but may be delayed for several minutes. 12 to 14 cycle spindle tracings appear with occasional slow triphasic waves, known as K complexes.
Soon thereafter, cycles ranging from 4 to 0.5 cycles per second appear. These are known as delta waves. When occupying less than 50% of the tracing, this is designated as stage 3 sleep. When delta waves account for more than 50% of the EEG tracing, stage 4 is achieved. Taken together, stages 3 and 4 are known as delta sleep or slow wave sleep (SWS).
In the transition from full wakefulness to somnolence, drowsiness, slumber, and finally sleep, waking EEG patterns give way to stages 1 through 4 NREM sleep. Delta sleep provides the most recuperative, highly quality sleep.
Individuals afflicted with initial insomnia have difficulties transitioning from the waking state to stages 1 and 2, and on to stages 3 and 4.
The disclosed method and apparatus aim to assist in the therapy of the most common manifestation of sleep dysfunction, namely the difficulty in falling asleep, so-called initial insomnia.
A way of doing so would be to prompt sleep-generating brain waves in brain sleep centers by stimulating sensory organs such as the skin, the visual senses, and the auditory senses with delta rhythms.
The delta wave prompting, importantly, is preferably individualized. Indeed, individuals show important variations in their preferences for the frequencies and the properties of the vibrations, and their translation into sound and color.
Electroencephalographic (EEG) studies have delineated, with ever-increasing precision, the architecture of normal and abnormal sleep patterns. A unifying principle applicable to the nervous system is that every neuron in the nervous system finds connections to every other neuron.
As an example, a stimulus applied to the skin, such as a vibration, will travel through nervous system networks, eventually impacting upon and resonating into all cortical and subcortical structures, including the sleep centers.
The initial stages of sleep show characteristic brain wave configurations, namely slow waves and delta waves. Encephalographically-speaking, individuals afflicted with initial insomnia have difficulties in making the transition from waking brain wave patterns to patterns associated with the onset of normal sleep.
The method and apparatus may encourage this transition using vibrational prompting. In addition, auditory, visual, and electrophysiological stimulation contribute to impel the waking brain into adopting theta, and eventually, delta brain wave configurations.
Neurophysiological prompting is a process by which an external stimulus acts as an inducer for a desired physiological response. In this case, the desired response is the generation and the maintenance of delta sleep waves.
In order to facilitate the transition from the waking state to sleep, vibrational prompting can be synchronized to theta and delta wave frequencies. This vibrational prompting may be supplemented or supplanted by auditory, visual, and subliminal or para-subliminal electro-physiological stimulation.
The ability to perceive vibrational stimulation is called pallesthesia. Receptors in the skin and deeper tissues, including Pacinian corpuscules, relay their messages to the dorsal columns of the spinal cord, making their way to the thalamus and from there to somesthetic cortical areas for detailed recognition.
Along this trajectory, communications are made with multiple areas of the brain, including deeper structures. These include the hypothalamic sleep centers. In addition, once having reached the somesthetic cortex, vibrational impulses freely extend their reach into other cortical areas including the frontal, temporal, and occipital lobes. For example, it is appreciated that vibrations applied to the skin may be perceived visually.
Synesthesia is the phenomenon which describes such cross-sensory perception. The significance of this cross-sensory phenomenon is that, for example, a vibrational stimulus applied anywhere on the body will, given adequate time and repeated applications, create neural reverberations into many areas of the nervous system. If this vibrational stimulus is given a delta frequency, the effect will eventually make its way into brain sleep centers, which will be prompted to mimic this sleep-inducing rhythm.
The apparatus generates a desired brain wave frequency through a microprocessor unit. The frequency may be selected by the user, or may be predetermined. Thus, the unit frequency setting may be set anywhere from 8 to ½ cycles per second. Some individuals find that inducing theta waves (8 to 4 cycles per second) automatically paves the way for delta wave production. Others will prompt delta waves from the start.
Other options are possible. The unit, for example, may emit a sequential progression of frequencies which mimic the transition from the waking state (descending from 12 to 8 cycles per second), to stage 2 sleep (descending from 8 to 4 cycles per second), then on to delta sleep, from 4 to ½ cycles per second. Each of these stages may be programmed as to their respective durations.
The frequencies generated by the microprocessor are capable of driving different modalities of stimuli, either individually, or in combination. Among them:
Thus, an apparatus and method can assist in the transition from wakefulness to sleep by means of theta and/or delta brain wave rhythmic prompting via vibrational stimulation applied to the skin. The apparatus is capable of supplementing or supplanting the vibrational stimulation with visual, auditory, and electrophysiological stimulation.
According to a preferred embodiment, the apparatus may comprise:
A preferred embodiment of a method may provide:
The anatomy and physiology of sensory mechanoreceptors. Physiological factors are useful to consider in determining the therapeutic functions to be provided according to the method and apparatus.
The skin generates a constant flow of information, sending it to the spinal cord and the central nervous system for instantaneous processing and response. This information is essential for the organism's function and survival. Sensing the shape and feel of objects, their temperature, their movements and their possible injurious nature requires skin sensors that quickly translate many forms of mechanical energy in the environment into neurological signals.
Skin sensors are microorgans that inform on texture, pressure, heat, cold, vibration, and, importantly, on trauma and inflammation. For the latter, they generate pain signals.
Beyond skin, in deeper connective tissues of muscles, tendons and joints, other microorgans (e.g., spindles) also convey neurological information on body position and motion.
Several types of skin sensors convey specific neurological information to the spinal cord and the central nervous system. Many receptors, however, while specialized, show some degree of cross-function. A touch sensor, for example, given a certain stimulus may, in addition to producing a signal of touch, also generate feelings of pressure.
The speed of nerve transmission from skin sensors to the spinal cord, and eventually to the brain, depends on the diameter of conducting nerve fibers, and on the degree to which they are sheathed in myelin, an insulating complex lipid.
The highly myelinated A fibers are large neuronal cables with conduction velocities of 70 to 120 meters/second. They carry sensation of proprioception, touch and pressure. C fibers, on the other hand, thin and unmyelinated, have conduction velocities approximating 1 meter/second. They carry pain sensations.
Sensory fibers with various conduction velocities conveying qualitatively different messages converge to the dorsal columns of the spinal cord, where they ascend to the medulla oblongata, the pons, the midbrain, and on to the thalamus, an ancient evolutionary brain structure. There, raw sensations gain conscious perception. Thalamic projections forward data to the post central gyms in the cortex, where sensations are distilled into their finer subtleties via association networks. By way of cortical connections to the speech areas, for example, pain may be described as burning, aching, throbbing, dull, sharp or lancinating; and vibrations may be perceived as soothing, relaxing, or annoying.
The skin transmits to the brain a variety of signals that give information on touch, vibration, cold, heat, pressure, and injury (which may be mechanical, chemical or electrical).
All skin and deeper tissue sensors convert stimuli in the environment into nerve impulses, which are basically electrochemical signals. How stimuli are presented (e.g., intensity, duration, quality) and perceived, forms the science of Psychophysics. How these electrical stimuli are eventually converted into the dimension of consciousness, for conscious perception, is unknown.
To achieve the task of translating a complex and fast-changing environment into sensory language, specialized tissue sensors have been developed.
These sensors are fairly specific (e.g. light touch is only perceived as light touch and not as cold). However, given greater stimulation (e.g. such as pressure, added to vibration), many more receptors will be stimulated to fire and signals will thus have more representation and input impact in the brain.
The signals from the skin receptors course through the spinal cord to reach the posteroventral nucleus of the thalamus. From there, they are projected, via the thalamo-cortical projections, to the 6 layers of the post-central gyms of the parietal lobe of the cortex, where they are given elaborate conscious meaning (e.g., differentiating the touch of velour from the touch of silk).
The central nervous system is completely interconnected via direct, circuitous, and feedback connections. In the thalamus, for example, the posteroventral nucleus of the thalamus has connections to all other thalamic and other nuclei, including the suprachiasmatic nucleus, involved in circadian rhythms and sleep. In other words, (pleasant) stimulation to the posteroventral nucleus will, especially if persistently continuous and rhythmical—for example at a rhythm of 1 to 8 Hz—make their way to the suprachiasmatic nucleus. The neurons in that nucleus will be prompted by these signals to generate neural signals in synchrony with them, sending signals having relevance to sleep to many regions of the brain. The signals it sends to the cortex will translate into delta and theta brain waves.
The above phenomenon invokes principles of neural synchronicity (where rhythmic signals have added power to involve more and more neurons), recruitment and neural entrainment, where neurons are increasingly coaxed into participation.
In this method and apparatus, optimal and pleasant vibrational stimuli are proposed to stimulate the posteroventral nucleus. With the addition of skin pressure, these stimuli come to have greater impetus.
Skin sensors work by mechanical deformation of their membranes. This deformation causes ion channels to open, thus creating depolarization and impulse discharge.
Several types of sensors found in the human skin and in deeper tissues provide a remarkable array of instantaneous information about many of the environment's variegated features:
An intrinsic component of vibrational stimuli is pressure, which allows vibrations to displace tissues. In order to be maximally effective for a particular clinical task, vibration and pressure are adjusted to interface with the dynamics of skin receptor function, and with the mechanical properties of skin tissues, such as firmness and elasticity. At a pressure of 50 g/cm2, for example, only a limited number of receptors will be stimulated. At a pressure of 1 kg/cm2, many more receptors will be activated. The device preferably has a capacity to apply pressures to skin ranging from 25 g/cm2 to 1 kg/cm2 while generating vibrations.
Vibration and pressure can be adjusted separately. At a given vibratory rate, for example, light pressure will impart vibrations to superficial tissues only. At greater pressures, vibrations will impact deeper tissue depths.
Lateral displacement of vibrational stimuli, or vibrational amplitude, is important for stimulating skin receptors that are far apart. The minimal amplitude, corresponding to two-point skin discrimination is about 1 mm. The device is preferably capable of generating vibrations with amplitudes ranging from 1 mm to 1.5 cm.
Irregular surface features on the device may augment the effectiveness of the stimulus. Indentations or corrugations may be linear, wavy, or circular, with a depth for example of 5 mm and a separation of about 1 mm to 1 cm.
Neuronal recruitment and sensory loading describe situations where the transmission of one modality, such as vibration, is assisted and even augmented by the stimulation of other receptors that use adjacent pathways to the spinal cord and brain (e.g., pressure, heat). The selective loading of sensory networks will produce increased traffic to the brain, involving more of its circuits, thus enhancing the influence of stimuli.
In view of the foregoing considerations, the disclosed method and apparatus provide vibrational stimuli configured to elicit selected mechanoreceptor skin responses in subjects. In addition, provision is made in the portion of the device that actually apposes itself to the skin surface of the subject, the interface. This interface, aside from the main vibrational stimulus it imparts (e.g., ½ to 8 Hz), may also impart subliminal and other vibrations of other frequencies concomitantly (8 to 250 Hz), in order to enhance neural recruitment. Additionally, the interface may also transmit heat to recruit warmth sensors; and it may be made of material whose surface is designed to stimulate touch and texture receptors in optimal fashion.
Thus, the method and apparatus create vibrational stimuli that are adapted to the physiology and neurology of the human skin; and to the properties of the nervous system, namely neural recruitment and sensory loading.
Different receptors may respond best to horizontal, vertical, or circular motions. This is due to their anatomy and their orientation in the skin. Vibrational stimuli, therefore, are best provided so that they can involve all these planes. Horizontal circular motions may be made to possess a vertical component so that vibrational stimuli may adopt a smooth repetitive 3-dimensional oscillation.
Other features and advantages of the disclosed method and apparatus will become apparent from the following description of embodiments, which refers to the accompanying drawings.
The programmable microprocessor has a variety of functions. Foremost is the rhythm function programmed through control (5a). The rhythm selection is shown on the LCD display (3). The rhythm control may select a fixed rhythm, or may select a sequence of rhythms, such as a rhythm progression from alpha (12 to 8 cycles per second), to theta (8 to 4 cycles per second), on to delta (4 to ½ cycles per second), for example.
As indicated above, frequency ranges of ½ to 8 Hz and preferably including 8-250 Hz are provided. The motor unit (10) is preferably capable under control of the microprocessor (7) of horizontal, vertical, circular and 3-dimensional movements, or at least some of these in combination.
The respective rhythms may be generated for variable corresponding lengths of time. The timer control (5f) programs the desired time parameters of the unit including automatic shut off and re-start.
The apparatus presents as a flat pad made of pliable and electroconductive material, such as, for example, carbon silicone. It is thin and comfortable enough to rest one's head upon it. Yet, it may be apposed to any part of the body. In the illustration in
The functions of the sleep pad of greatest therapeutic value are believed to be the vibrational capacity of the motor unit (10), and the warmth-generating heater (14). However, in addition, it has the capacity, predicated upon individual choice or therapeutic preference, to express rhythmic light, rhythmic sound, and rhythmic electrophysiological stimuli.
The sleep pad is provided with an energy source, a battery,
The microprocessor may be programmed to:
In a preferred embodiment, shown in
In the embodiment of
Preferably, a suitable heater (not shown) may be provided, for maintaining the medium 2 at a comfortable temperature, as already described.
The embodiment of
Although embodiments have been described in some detail, it will be understood by those skilled in the art that changes and modifications may be practiced without departing from the spirit and scope thereof
The present application is a continuation-in-part of U.S. Ser. No. 11/075,075 filed Mar. 8, 2005, incorporated herein by reference.
Number | Date | Country | |
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Parent | 11075075 | Mar 2005 | US |
Child | 12723363 | US |