Diverse studies have shown that the behavioural, cellular and physiological functions of animals can be affected by magnetic stimuli. Weak magnetic fields exert a variety of biological effects ranging from alterations in cellular ion flux to modifications of animal orientation and learning, and therapeutic actions in humans.
There are several theories addressing the mechanism of the effect of low frequency magnetic field exposure on tissues. For example, low frequency magnetic field exposures have been proposed to exert their effect(s) through the induction of electric currents. Weak magnetic fields have also been proposed to be detected by particles of magnetite in tissue and by virtue of this detection, have a physiological effect; however, this magnetite based mechanism is not widely believed (Prato, F. S.; Kavaliers, M.; Carson, J. L. L. (1996) Behavioral evidence that magnetic field effects in the land snail, Cepaea nemoralis, might not depend on magnetite or induced electric currents. Bioelectromagnetics. 17:123-130.).
Extremely low frequency (ELF) magnetic fields are a physical agent which have little attenuation in tissue and therefore, can be used to alter endogenous processes provided they can be detected and their detection coupled to a physiological process. It has now been shown that magnetic fields may be designed as time varying signals such that they can be used to alter specific targeted physiological processes and in this manner can be used to treat/modify various neurological and physiological conditions and behaviours. U.S. Pat. No. 6,234,953 to Thomas et al., the contents of which are incorporated herein by reference, discloses such a method of using low frequency magnetic pulses to treat physiological, neurological and behavioural disorders.
Devices for generating electromagnetic waveforms to stimulate a subject are also known. For example, U.S. Pat. No. 6,312,376 to Koren et al. discloses an apparatus for generating electromagnetic waveforms that includes a signal generator and a selector. The selector applies mathematically-derived waveforms generated by the processor of the signal generator onto selected channels in response to channel select input. The generated waveforms are applied to electromagnetic devices thereby to expose a subject wearing the electromagnetic devices to the generated electromagnetic waveforms. Although this apparatus is satisfactory, improvements are desired.
PCT Application Publication No. WO 96/11723 to Edwards et al. discloses an electromagnetic therapy device that stores waveform parameters such as pulse width, duration, duty cycles and frequency, execution order, change table and various counters in order to effect implementations of varying sequences of square waveforms. During operation, a microprocessor imports these operational parameters and produces a corresponding sequence of digital values. The digital values, together constituting a square waveform, are then converted into electrical current by a waveform generator and applied to an inductor in order to produce the resultant magnetic fields. The Edwards et al. device requires its microprocessor to execute several instructions in order to generate each digital value in real-time. In doing so, the microprocessor is occupied for several cycles per digital value produced and is accordingly restricted in terms of the frequency at which it can produce those values. As a result, Edward's device is inherently limited by its design to producing waveforms with frequencies far below the clock speed of its microprocessor, and a much faster and accordingly expensive microprocessor is required in order to overcome the limitation. Furthermore, Edward's device recalculates a change in waveform characteristics only after a session counter has reached a certain parameter value as reflected in a change table. Thus, the device is restricted to producing square waveforms in the interim, and uses up cycles when constantly comparing the counter to the change table, further restricting the frequency of the resultant waveforms.
It is therefore an object of the present invention to provide a novel portable electrotherapy device for generating specific low frequency pulsed magnetic fields that are used to modify a variety of physiological, neurological and behavioural conditions in vertebrates and invertebrates.