Patent No. 5899922 Manipulation of nervous systems by electric fields

 

Patent No. 5899922

Manipulation of nervous systems by electric fields (Loos, May 4, 1999)

Abstract

Apparatus and method for manipulating the nervous system of a subject through afferent nerves, modulated by an externally applied weak electric field. The field frequency is to be chosen such that the modulation causes excitation of a sensory resonance. The resonances found so far include one near 1/2 Hz which affects the autonomic nervous system, and a resonance near 2.4 Hz that causes slowing of certain cortical processes. Excitation of the 1/2 Hz autonomic resonance causes relaxation, sleepiness, ptosis of the eyelids, or sexual excitement, depending on the precise frequency used. The weak electric field for causing the excitation is applied to skin areas away from the head of the subject, such as to avoid substantial polarization current densities in the brain. Very weak fields suffice for bringing about the physiological effects mentioned. This makes it possible to excite sensory resonances with compact battery powered devices that have a very low current consumption. The method and apparatus can be used by the general public as an aid to relaxation, sleep, or sexual arousal, and clinically for the control and perhaps the treatment of tremors and seizures, and disorders of the autonomic nervous system, such as panic attacks.

Notes:

SUMMARY

Experiments have shown that weak electric fields of frequency near 1/2 Hz applied externally to the skin of a subject can cause relaxation, doziness, ptosis of the eyelids, or sexual excitement, depending on the precise frequency used. In these experiments the electric field was applied predominantly to skin areas away from the head, thereby avoiding substantial polarization current densities in the brain. Apparently, the external electric field somehow influences somatosensory or visceral afferent nerves, which report the effect to the brain. Although the mechanism whereby the field acts on the afferents is unknown, the effect must take the form of a slight modulation of the firing patterns of the nerves, because the polarization current densities induced by the field are much too small to cause firing of the nerve. If the applied external field is periodic, so will be the modulation of the firing patterns of affected afferent fibers, and the brain is then exposed to an evoked periodic signal input. Apparently, this signal input influences certain resonant neural circuits, the state of which has observable consequences. Since the resonances are excited through somatosensory or visceral afferents, they are here called "sensory resonances".

Besides the resonance near 1/2 Hz that affects the autonomic nervous system, we have also found a resonance near 2.4 Hz which slows certain cortical processes. For both resonances the external electric field on the skin must lie in a certain range of values for the physiological effects to occur. This "effective intensity window" can be determined accurately for the 2.4 Hz resonance, by measuring the time needed to count silently backward from 100 to 70.

The effective intensity window depends on the number of afferents modulated by the field. This "bulk effect" is important for the proper use of the invention, and has therefore been explored in preliminary experiments. At the lower boundary of the window the external field strengths are very small, down to 10 mV/m when a large skin area is exposed to the field. The fact that very small external field strengths suffice for the excitation of sensory resonances through modulation of afferents allows the use of small battery-powered electric field generators that can be used conveniently by the general public as an aid to relaxation, sleep, or sexual excitement, and clinically for the control and perhaps a treatment of tremors and seizures, and disorders of the autonomic nervous system such as panic attacks.

Compliance of the devices with the MPRII guidelines on field limits in the ELF and VLF frequency bands is easily achieved.

The field generators shown involve simple low voltage generators based on 555 type timer chips, and field electrodes that are small enough to fit in a single small casing, such as a powder box.

Although the mechanism of electric field modulation is unknown, candidates for cutaneous receptors that may be susceptible to this modulation are indicated.

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The invention is not limited by the embodiments shown in the drawings and described in the specification, which are given by way of example and not of limitation, but only in accordance with the scope of the appended claims.

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