Abstract:
An apparatus for generating electromagnetic waveforms to stimulate a subject includes an electromagnetic waveform signal generator to generate analog signals representing desired electromagnetic waveforms. A selector responsive to channel select input applies the analog signals to selected output channels of the selector. Electromagnetic devices are coupled to the output channels of the selector to convert analog signals into electromagnetic waveforms. The electromagnetic devices coupled to the selected output channels are driven by the analog signals to expose a subject wearing the electromagnetic devices to the desired electromagnetic waveforms.

Description:
FIELD OF THE INVENTION 
     The present invention relates to neuropsychology and in particular to a method and apparatus for generating electromagnetic waveforms to stimulate a subject. 
     BACKGROUND OF THE INVENTION 
     Diverse studies have shown that the behavioral, 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 that magnetic field exposure has on tissues. For example, low frequency magnetic field exposures have been proposed to exert their effect(s) through induction of electric currents. Although not widely believed, it has also been proposed that weak magnetic fields are detected by particles of magnetite in tissue and by virtue of this detection have a physiological effect. 
     Although the mechanism of the effects of magnetic field exposure on tissues is uncertain, it is clear that magnetic fields are a physical agent which have little attenuation in tissue and therefore, can be used to alter endogenous processes provided the magnetic fields can be detected and their detection coupled to a physiological process. In view of this, it is desired to expose subjects to magnetic fields to treat physiological, neurological and behavioral disorders and to determine the effect of a variety of magnetic stimuli on subjects. 
     It is therefore an object of the present invention to provide a novel method and apparatus for generating electromagnetic waveforms to stimulate a subject. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention there is provided an apparatus for generating electromagnetic waveforms to stimulate a subject. The apparatus includes an electromagnetic signal generator generating analog signals corresponding to electromagnetic waveforms. A selector is responsive to channel select input and applies the analog signals output by the electromagnetic signal generator onto selected output channels thereof. Electromagnetic devices are coupled to the output channels of the selector and convert the analog signals into electromagnetic waveforms to expose a subject wearing the electromagnetic devices to the electromagnetic waveforms. 
     Preferably, the electromagnetic waveform signal generator is programmable. In a preferred embodiment, the electromagnetic waveform signal generator includes a processing unit to generate digital representations of the desired electromagnetic waveforms and an analog to digital converter coupled to the processing unit to convert the digital representations into corresponding analog signals. The processing unit preferably is coupled to the selector and provides the channel select input. 
     Preferably the processing unit is programmable to set a desired delay between successive digital samples of the digital representations output by the processing unit. It is also preferred that the processing unit is programmable to set a sequence of selected output channels on which the analog signals are to be applied. The processing unit is programmable to repeat the sequence a desired number of times, to set the duration the analog signals are output on each selected output channel in the sequence, to set a desired delay between repetition of the sequence, and to set a desired acceleration sequence. The acceleration sequence determines a change in the duration the analog signals are applied to each successive selected output channel in the sequence. 
     Preferably, the electromagnetic devices are arranged in pairs with each pair being coupled to a respective output channel of the selector. The electromagnetic devices are attached to head wear to be worn by the subject and are in the form of solenoid assemblies. Selected pairs of the solenoid assemblies are in phase and selected other pairs of the solenoid assemblies are out of phase. 
     According to another aspect of the present invention there is provided an apparatus for generating electromagnetic waveforms to stimulate a subject that comprises a processing unit having memory storing at least one digital representation of a desired electromagnetic waveform. A digital analog to converter is coupled to the processing unit to convert digital representations of electromagnetic waveforms received from the processing unit into corresponding analog signals. A selector is responsive to channel select input from the processing unit to apply the analog signals onto selected output channels of the selector. Electromagnetic devices are coupled to the output channels of the selector to convert analog signals into electromagnetic waveforms. The electromagnetic devices that are coupled to the selected output channels are driven by the analog signals to expose a subject wearing the electromagnetic devices to the electromagnetic waveforms. The processing unit is programmable to expose the subject to a desired sequence of tailored electromagnetic waveforms to provide a desired stimulus to the subject. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     An embodiment of the present invention will now be described more fully with reference to the accompanying drawings in which: 
     FIG. 1 is a schematic diagram of an apparatus for generating electromagnetic waveforms in accordance with the present invention; 
     FIG. 2 a  is a table of points along a digital representation of an electromagnetic waveform; 
     FIG. 2 b  is an illustration of an analog conversion of the digital representation of FIG. 2 a;  and 
     FIG. 3 is a table showing a digital to analog conversion of points along a digital representation of an electromagnetic waveform. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIG. 1, an apparatus for generating electromagnetic waveforms to which a subject is to be exposed is shown and is generally indicated to by reference numeral  10 . As can be seen, apparatus  10  includes a processing unit in the form of a personal computer  12 . Connected to a parallel port  12   a  of the personal computer  12  is an interface  14  including an 8-bit digital to analog converter  16  such as that manufactured by National Semiconductor under part No. DAC0800LCN, and a two-stage direct coupled operational amplifier circuit  18  utilizing LM741CN operational amplifiers. Operational amplifier circuit  18  is powered by an ELPAC WM113 DC power supply (+5 v@860 ma;+/−12 v@300 ma)  20 . 
     The output of the digital to analog converter  16  is conveyed to a one-of eight channel selector  24  including a plurality opto-couplers. Selector  24  is also powered by power supply  20  and is responsive to input received from the parallel port  12   a  of personal computer  12  to enable output channels of the selector  24  on which the output of digital to analog converter  16  is to be applied. 
     Each output channel of the selector  24  is electrically coupled to a pair of solenoid assemblies  30  (only one pair of which is shown) in parallel, by a shielded cable  32 . The connections between the selector output channels and the solenoid assemblies are such that some of the pairs of solenoid assemblies  30  are in phase (i.e. the solenoid assemblies are connected in North to North magnetic polarity) and some of the pairs of solenoid assemblies  30  are out of phase (i.e. the solenoid assemblies are connected in North to South magnetic polarity). The solenoid assemblies  30  of each pair are attached to a headband  34  to be worn by a subject and are positioned on the headband so that the solenoid assemblies of each pair are diametrically opposed. Adjacent solenoid assemblies  30  are separated by a distance equal to approximately 0.8 inches. 
     Each solenoid assembly  30  includes a solenoid constructed from a reed relay (Intertan 275-232) with the reed switch removed and replaced by a steel nail core. The solenoids are housed within casings attached to the headband  34  by way of hook and loop fabric. 
     The electromagnetic waveforms to which subjects are to be exposed are digitally stored in the personal computer  12  as DAC (see FIG. 2 a ) files  40  and can be derived from mathematical equations, spoken words or custom designed. Each DAC file  40  includes a list of individual points  42  representing points along the corresponding electromagnetic waveform together with a header  44  indicating the number of individual points that are stored in the DAC file. The DAC file is either in the form of a DOS-text or ASCII-text file with one individual point entry per line. Each individual point has a value in the range of 0 to 255 represented as an 8-bit binary number. FIGS. 2 a  and  2   b  illustrate an example of a DAC file  40  that is a digital representation of an electromagnetic square waveform and its analog equivalent. As can be seen, the DAC file header  44  indicates that eight individual points  42  are in the DAC file  40 . 
     The value assigned to each individual point in a DAC file corresponds to an analog output voltage. FIG. 3 shows the conversion of individual point values to analog voltage levels. As can be seen, value  255  (binary “11111111”) corresponds to an analog voltage equal to 6 volts, value  127  (binary “01111111”) corresponds to an analog voltage equal to 0 volts, and a value  0  (binary “00000000”) corresponds to an analog voltage equal to −6 volts. 
     Stored within the personal computer  12  is a computer program which when executed, outputs DAC files  40  to the digital to analog converter  16  and enables selected channels of the selector  24  to drive selected pairs of the solenoid assemblies  30  thereby exposing the subject to electromagnetic waveforms. The computer program allows a user to: 
     (i) select the form of the electromagnetic waveforms to be generated by creating DAC files; 
     (ii) determine the delay between each individual point of an electromagnetic waveform being generated (i.e. set the frequency of the electromagnetic waveform); 
     (iii) determine the number of times the electromagnetic waveform is to be repeated; 
     (iv) determine the delay between each repeat of the electromagnetic waveform; 
     (v) determine the channel sequence on which the electromagnetic waveform is to be output (i.e. sequence limit); 
     (vi) determine the duration the electromagnetic waveform is to be applied to each channel (i.e. sequence interval); and 
     (vii) determine a sequence acceleration for the repeated electromagnetic waveform. 
     For example, if the sequence limit is set equal to four, the sequence acceleration is set equal to −2 msecs, the sequence interval is set equal to 10 msecs, and a DAC file  40  is selected to be repeated three times, the electromagnetic waveform would firstly be presented on channel  1  for 10 msecs, then on channel  2  for 8 msecs, and then on channel  3  for 6 msecs and then lastly on channel  4  for 4 msecs. After that the above sequence would be repeated until the sequence had been output a total of four times. 
     In use, an operator creates DAC files  40  representing the desired electromagnetic waveforms to which a subject is to be exposed. Once the operator has created the DAC files, the operator assigns values to the above described parameters. 
     Once the parameters have been assigned values, the headband  34  is placed on the head of a subject. The computer program is then executed by the personal computer  12  causing the computer program to select the DAC file  40  to be processed and causes the personal computer to output the individual points with the set delay between individual points as 8-bit binary values to the digital to analog converter  16  via the parallel port  12   a.  The personal computer  12  also outputs 3-bit values representing the channel sequence via the parallel port  12   a  that are conveyed to the selector  24 . The selector  24  in turn enables the desired channels. 
     As the digital to analog converter  16  receives the output 8-bit binary values, it converts the binary values to corresponding analog signals and supplies the analog signals to the selector  24 . The selector in turn passes the analog signals onto its enabled output channels. 
     As the analog signals appear on the channels, the selector output solenoid assemblies  30  are driven to expose the subject wearing the headband to the desired electromagnetic waveforms. By using parameter passing and batch processing, the subject can be exposed to a series of different electromagnetic waveforms for different durations and on different channels. 
     Although a preferred embodiment of the present invention has been described, those of skill in the art will appreciate that variations and modifications may be made without departing from the spirit and scope thereof as defined by the appended claims.