Patent No. 7033312 Magnetic field stimulation techniques
Patent No. 7033312
Magnetic field stimulation techniques (Rohan, et al., Apr 25, 2006)
Abstract
The invention involves enhancing brain function by stimulating the brain using magnetic fields. Applications of the new methods include improving the condition of individuals with cognitive disorders, such as depression, and studying the effects of neural stimulation using induced electric fields. These techniques can avoid deleterious effects of psychotropic pharmaceutical treatments, and provide a relatively safe, comfortable, inexpensive means of direct cranial stimulation.
Notes:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation of incorporates by reference U.S. patent
application Ser. No. 09/839,258, filed Apr. 20, 2001, which now is U.S. Pat.
No. 6,572,528.
TECHNICAL FIELD
This invention relates to magnetic stimulation techniques, and more particularly
to neural stimulation using a magnetic field.
BACKGROUND
Repetitive transcranial magnetic stimulation (rTMS) has been used with the goal
of treating depression, see, e.g., George et al., The Journal of Neuropsychiatry
and Clinical Neurosciences, 8:373, 1996; Kolbinger et al., Human Psychopharmacology,
10:305, 1995.
One example of an rTMS technique uses a figure-8 surface coil with loops that
are 4 cm in diameter (Cadwell, Kennewick, Wash.). This coil is placed next to
the scalp, and is usually positioned to direct the magnetic field at the prefrontal
cortex of the brain, see, e.g., George et al., The Journal of Neuropsychiatry
and Clinical Neurosciences, 8:373, 1996. An electric current is run through
the magnetic coil to generate a magnetic field, specifically a sequence of single-cycle
sinusoidal pulses where each pulse has a frequency of approximately 1800 Hz
(or about 560 microseconds per pulse). These pulses are delivered at a repetition
rate of 1 to 20 Hz (i.e., one pulse every 0.05 to 1 second), see, e.g., George
et al, Biological Psychiatry, 48:962, 2000; Eschweiler et al, Psychiatry Research:
Neuroimaging Section, 99:161, 2000.
Some subjects have declined participation in rTMS studies due to pain induced
in the scalp. In addition, seizures have been reported as a result of rTMS treatment,
see, George et al, Biological Psychiatry, 48:962, 2000; Wasserman, Electroencephalography
and Clinical Neurophysiology 108:1, 1998.
SUMMARY
The invention concerns enhancing brain function using novel magnetic field techniques.
These magnetic field techniques use low field strengths, high repetition rates,
and uniform gradients to improve brain function.
In one aspect of the present invention, a subject is selected for enhancement
of brain function using a magnetic field. The subject's head is then subjected
to a time-varying magnetic field having a maximum strength of less than about
50 G.
Advantages of this aspect of the invention include the following. Subjects with
cognitive impairments may benefit from the new treatment by the lessening of
the severity of the condition. Treatment techniques using this method can be
administered inexpensively with relative safety and comfort, and offer a substitute
for or complement to treatment by medication. Applications of the new methods
include improving the condition of individuals with cognitive disorders, such
as depression, and studying the effects of brain stimulation using induced electric
fields.
Embodiments of this aspect of the invention can include one or more of the following
features. After treating the subject (e.g., a human patient), the subject can
be evaluated for enhanced brain function. The magnetic field can have a maximum
strength of less than about 10 G. The field can also be a gradient magnetic
field that is substantially uniform (i.e., a magnetic field one or more of whose
x, y, or z direction components varies approximately linearly in space; that
is, has a constant gradient to within, e.g., 10%) and unidirectional over the
relevant volume (e.g., the entire brain, or a region of interest of the brain
such as the prefrontal cortex). The gradient of the magnetic field can be less
than about 5 G/cm. The magnetic field can be generated using a sequence of trapezoidal
pulses of alternating polarity, where each pulse has a duration of about 1 millisecond.
In another aspect of the present invention, a subject is selected for enhancement
of brain function using a magnetic field. The subject's head is then subjected
to a time-varying gradient magnetic field that is substantially uniform and
unidirectional.
In another aspect of the present invention, a subject is selected for enhancement
of brain function using a magnetic field. The subject's head is then subjected
to a time-varying magnetic field generating by a sequence of pulses, each having
a duration of less than about 10 milliseconds.
Unless otherwise defined, all technical and scientific terms used herein have
the same meaning as commonly understood by one of ordinary skill in the art
to which this invention belongs. Although methods and materials similar or equivalent
to those described herein can be used in the practice or testing of the present
invention, suitable methods and materials are described below. All publications,
patent applications, patents, and other references mentioned herein are incorporated
by reference in their entirety. In case of conflict, the present specification,
including definitions, will control. In addition, the materials, methods, and
examples are illustrative only and not intended to be limiting.
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