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Patent No. 6167304  Pulse variability in electric field manipulation of nervous systems (Loos, Dec 26, 2000)

Abstract

Apparatus and method for manipulating the nervous system of a subject by applying to the skin a pulsing external electric field which, although too weak to cause classical nerve stimulation, modulates the normal spontaneous spiking patterns of certain kinds of afferent nerves. For certain pulse frequencies the electric field stimulation can excite in the nervous system resonances with observable physiological consequences. Pulse variability is introduced for the purpose of thwarting habituation of the nervous system to the repetitive stimulation, or to alleviate the need for precise tuning to a resonance frequency, or to control pathological oscillatory neural activities such as tremors or seizures. Pulse generators with stochastic and deterministic pulse variability are disclosed, and the output of an effective generator of the latter type is characterized.

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 skin area of application and the precise frequency used. In these experiments the electric field was applied predominantly to selected skin areas away from the head, thereby avoiding substantial polarization current densities in the brain. Apparently, the external electric field 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 modulation of the spiking patterns of the nerves, because the electric current densities induced in the tissue are much too small to cause firing of a normally quiescent nerve. If the applied external field is periodic, so will be the modulation of the spiking patterns of affected afferent fibers, and the brain is thus exposed to an evoked periodic signal input. It appears that this signal excites certain neural circuits to resonance, with observable consequences. Since the resonances are excited through somatosensory or visceral afferents, they are 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 strength of the external electric field on the skin must lie in a certain range for the physiological effects to occur. This range, which is called the "effective intensity window", depends on the number of afferents modulated by the field. When a large skin area is exposed, the field strengths at the lower window boundary are very small. The effectiveness of weak fields 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 control and perhaps 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, because reliance on the resonance mechanism allows the use of weak fields.

The field generators shown involve simple low voltage pulse generators based on 555-type timer chips. The field electrodes can be made small enough to fit, together with the generator, in a single small casing.

Habituation of the nervous system to the electric field stimulation can be thwarted to a considerable extent by introducing variability into the field pulses. Simple circuits are shown that provide stochastic and deterministic pulse variability. The output of a circuit with the latter variability has been measured and characterized. In experiments, the small battery-powered device with this circuit has consistently induced in a male subject sexual excitement for up to an hour duration.
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The method is expected to be effective also on certain animals, and applications to animal control are therefore envisioned. The nervous system of humans is similar to that of other mammals, so that sensory resonances are expected to exist in the latter, albeit with somewhat different frequencies. Accordingly, in the present invention, subjects generally are mammals.

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 limitaion, but only in accordance with the scope of the appended claims.

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