U.S. patent application number 14/223887 was filed with the patent office on 2014-07-24 for methods and apparatus for transcranial stimulation.
This patent application is currently assigned to ElectroCore, LLC. The applicant listed for this patent is ElectroCore, LLC. Invention is credited to Bruce J. Simon.
Application Number | 20140207224 14/223887 |
Document ID | / |
Family ID | 41432010 |
Filed Date | 2014-07-24 |
United States Patent
Application |
20140207224 |
Kind Code |
A1 |
Simon; Bruce J. |
July 24, 2014 |
METHODS AND APPARATUS FOR TRANSCRANIAL STIMULATION
Abstract
The present invention provides systems, apparatus and methods
for applying electric current to neurons in the brain to treat
disorders and to improve motor and/or memory functions in a
patient. In a method according to the invention, an electrode is
positioned adjacent to and spaced from the skin surface of the
patient's head and an electric current is applied through the
electrode to a target region in the brain to modulate one or more
neurons in the target region. The electrode is housed within an
enclosure and spaced from the skin surface so that the electrode
does not directly contact the patient's tissue, which reduces the
potential for collateral tissue damage or necrosis and shields the
electrode from the patient's tissue which substantially inhibits
Faradic products (e.g., H.sup.+, OH.sup.-, H.sub.2O.sub.2) of the
electrode from reaching the target site.
Inventors: |
Simon; Bruce J.; (Mountain
Lakes, NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ElectroCore, LLC |
Basking Ridge |
NJ |
US |
|
|
Assignee: |
ElectroCore, LLC
Basking Ridge
NJ
|
Family ID: |
41432010 |
Appl. No.: |
14/223887 |
Filed: |
March 24, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12548569 |
Aug 27, 2009 |
8682449 |
|
|
14223887 |
|
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Current U.S.
Class: |
607/153 ;
607/115 |
Current CPC
Class: |
A61N 1/36025 20130101;
A61N 1/0472 20130101; A61N 1/205 20130101; A61N 1/40 20130101; A61N
1/0408 20130101; A61N 1/36021 20130101; A61N 1/0456 20130101 |
Class at
Publication: |
607/153 ;
607/115 |
International
Class: |
A61N 1/04 20060101
A61N001/04 |
Claims
1. A method for improving motor and/or memory function in a patient
comprising: positioning an electrode adjacent to and spaced from a
skin surface of a head of a patient; and applying an electrical
impulse through the electrode to a target region in a motor cortex
of a brain of the patient, wherein the electrical impulse is
sufficient to modulate one or more neurons in the target region and
to improve a motor function in the patient.
2. The method of claim 11 further comprising housing the electrode
within an enclosure and contacting an outer wall of the enclosure
to the skin surface.
3. The method of claim 11 further comprising electrically coupling
the electrode to the skin surface.
4. The method of claim 3 wherein the electrically coupling step is
carried out by delivering an electrically conductive fluid between
the electrode and the skin surface.
5. The method of claim 4 further comprising: contacting the skin
surface with a contact element of an enclosure housing the
electrode; and delivering an electrically conductive fluid to an
interior of the enclosure to electrically couple the electrode to
the contact element.
6. The method of claim 1 wherein the electrical impulse is a direct
current between about 0.01 to 100 mA.
7. The method of claim 1 wherein the positioning step includes
spacing the electrode at least 3 cm away from the skin surface.
8. The method of claim 1 wherein the positioning step includes
spacing the electrode at least 8 cm from the skin surface.
9. The method of claim 5 wherein the electrically conductive fluid
comprises a gel material.
10. The method of claim 1 further comprising: positioning a second
electrode adjacent to and spaced from the skin surface; and
applying the electrical impulse from the first electrode through
the target region to the second electrode.
11. The method of claim 1 wherein the electrode is an anode.
12. The method of claim 1 wherein the electrode is a cathode.
13. The method of claim 1 wherein the electrical impulse is a
direct current from about 1 to about 10 mA.
14. The method of claim 1 wherein the electrical impulse is
sufficient to alter a firing rate of the one or more neurons in the
target region.
15. The method of claim 5 wherein the electrically conductive fluid
is saline.
16. The method of claim 5 wherein the electrically conductive fluid
is a buffered conductive solution.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a Continuation of U.S.
application Ser. No. 12/548,569 filed 27 Aug. 2009 now U.S. Pat.
No. 8,682,449 issued 25 Mar. 2014; which is incorporated herein by
reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to the delivery of electrical
energy to bodily tissues for therapeutic purposes, and more
specifically to devices and methods for treating various disorders
resulting from nerve transmissions in the brain.
[0003] The use of electrical stimulation for treatment of medical
conditions has been well known in the art for nearly two thousand
years. Electrical stimulation of the brain and the peripheral
nervous system and/or direct stimulation of malfunctioning tissue
are generally a completely reversible and non-destructive treatment
and holds significant promise for the treatment of many
ailments.
[0004] Transcranial direct current stimulation (tDCS) is being
studied for treatment of a number of conditions, such as improving
motor performance in healthy people, improving memory
consolidation, accelerating recovery from major stroke and the
treatment of migraines, bipolar disease, epilepsy, schizophrenia
and major depression. tDCS typically involves the application of
low frequency oscillatory currents or weak direct currents (e.g.,
about 1-2 mA) to modulate the activity of targeted neurons in the
brain. Typically, the electrode associated with the positive pole
or anode causes an increase in nerve activity while the electrode
associated with the negative pole or cathode causes a decrease in
nerve activity.
[0005] Several generations of neurophysiologic experiments have
shown that neurons respond to static (DC) electrical fields by
altering their firing rates. Firing increases when the anode is
located near the cell body and decreases when the field is
reversed. However, when the electrodes are placed on the scalp, the
current density produced in the brain is exceedingly small,
changing membrane potentials only by a fraction of a millivolt.
tDCS typically only influences the area of the brain directly
underneath the electrode that is close to the skull and thus is
more selective than other methods of brain stimulation.
Transcranial direct current stimulation is not "stimulation" in the
same sense as transcranial magnetic stimulation or the stimulation
of the brain and nerves with conventional techniques. It does not
appear to cause nerve cell firing on its own and does not produce
discrete effects such as the muscle twitches associated with
classical stimulation.
[0006] Schizophrenics often have what are called negative symptoms.
Negative symptoms include apathy, poor attention, poor grooming
habits and poor motivation. These symptoms have been associated
with under activity of the frontal lobes, particularly a brain area
called the left dorsolateral prefrontal cortex (LDPFC). Positive
schizophrenic symptoms such as hallucinations may be associated
with over activity in different brain areas, like the temporal
cortex. Thus, tDCS may be able to up regulate activity in the left
dorsolateral prefrontal cortex while simultaneously decreasing
activity in the temporal cortex. This could have a substantial
impact on a range of schizophrenic symptoms. For depression, tDCS
may be able to up regulate activity in the left dorsolateral
prefrontal cortex while simultaneously decreasing activity in the
right dorsolateral prefrontal cortex. This will likely have a more
robust antidepressant effect.
[0007] One of the limitations of current tDCS is that the electric
current can only be applied for a limited period of time and at a
limited power or voltage because the electrodes will begin to
damage the tissue they are in contact with. In light of this,
improved systems, devices and methods for the treatment of
disorders associated with nerve transmissions in the brain are
desired.
SUMMARY OF THE INVENTION
[0008] The present invention provides systems, apparatus and
methods for selectively applying electrical energy to body tissue.
Specifically, the present invention includes systems and methods
for applying low frequency oscillatory and/or direct current to
neurons in the brain to treat disorders or to improve motor and/or
memory functions in a patient.
[0009] In one aspect of the invention, an electrode is positioned
adjacent to and spaced from the skin surface of the patient's head
and a low frequency oscillatory or direct current is applied
through the electrode to a target region in the brain to modulate,
stimulate and/or inhibit one or more neurons in the target region.
In a preferred embodiment, the electrode is housed within an
enclosure and a portion of the enclosure is positioned in contact
with the skin surface. Thus, the electrode does not directly
contact the patient's tissue, which reduces the potential for
collateral tissue damage or necrosis and/or excessive electric
fields in the tissue. The enclosure physically shields the
electrode from the patient's tissue which substantially inhibits
Faradic products (e.g., H+, OH-, H2O2) of the electrode from
reaching the target site. In this manner, an electric current can
be applied to the electrode(s) without the danger of such Faradic
products reaching excessively high concentrations at the tissue
site. In addition, electric current can be delivered for a longer
period of time and/or at higher power levels than is conventionally
considered safe.
[0010] In certain embodiments, the electrode is the positive pole
or anode which causes an increase in firing of neurons located
close to the electrode. This up regulates these neurons and
increases their overall activity. In other embodiments, the
electrode is the negative pole or cathode which causes a decrease
in firing of neurons or down regulation of these neurons. In yet
other embodiments, the invention includes both an anode and a
cathode to increase the activity of certain neurons while
simultaneously decreasing the activity of other neurons within the
brain.
[0011] In a preferred embodiment, one or more enclosure(s) are
positioned against the patient's head and conductive fluid is
delivered within the interior of each enclosure. Electrical energy
is applied to the conductive fluid such that the electrical energy
passes through an ion-permeable section of one portion of the
enclosure to the target region within the brain. In an exemplary
embodiment, the electrical energy is applied to an electrode
positioned within a fluid passage or tube coupled to an
electrically conductive contact element, such as a conducting
gel-like material (e.g., hydrogel or the like). The contact element
is designed to conform to the patient's head and provide good
electrical contact to the skin surface. The fluid passage extends
away from the contact element to space the electrode from the
patient's tissue. The electrode may be spaced from about 1-20 cm,
preferably between about 3-8 cm, from the contact element.
[0012] In certain embodiments, the treatment electrode and the
enclosure are placed adjacent to or near the motor cortex of the
brain. In these embodiments, an electrical signal is applied to
neurons within the motor cortex to improve motor performance in
healthy people and/or to accelerate recovery from motor function
loss (e.g., major stroke).
[0013] In other embodiments, the treatment electrode and the
enclosure are placed adjacent to or near a target region in the
brain that is underactive or overactive, thereby resulting in a
disorder such as acute pain, epilepsy, fibromyalgia, schizophrenia
and major depression. In one such embodiment, an anode electrode is
placed near the left dorsolateral prefrontal cortex (LDPFC) to
increase the activity of the neurons in this region to treat
schizophrenia. In this embodiment, a cathode electrode may also be
placed adjacent to or near the temporal cortex to decrease activity
in this area. In the exemplary embodiment, the electrodes will up
regulate activity in the LDPFC while simultaneously down regulating
activity in the temporal cortex to treat a range of schizophrenia
symptoms.
[0014] In yet another embodiment, an anode electrode is placed
adjacent to or near the left dorsolateral prefrontal cortex and a
cathode electrode is placed adjacent to or near the right
dorsolateral prefrontal cortex. This will increase activity in the
LDPFC while decreasing activity in the RDPFC to treat major
depression.
[0015] In one embodiment, the device further includes a vacuum
source for aspirating the electrically conductive fluid from the
interior of the enclosure(s). The vacuum source may be a positive
source of aspiration with an aspiration passage coupled to the
interior of each enclosure or the device may be designed to simply
allow the fluid to evacuate the enclosure(s) through the same fluid
passage it entered through pressure differential, gravity, or the
like. Evacuating the conductive fluid deflates the enclosure(s) and
allows any excess Faradic products and/or heat to be evacuated from
the device. In this manner, the enclosure(s) may be periodically
evacuated to allow for periodic evacuation of excess Faradic
products and heat, which allows for higher power levels and/or
longer continuous use of the device in the patient. In some
embodiments, the device may be adapted for continuous circulation
of the electrically conductive fluid to reduce any build-up of heat
or Faradic products and ensure uniform temperatures at the outer
surface of the enclosure(s). These embodiments will allow the
device to use much higher power levels as the heat generated around
the electrode(s) and within the conductive fluid from the higher
power levels will be continuously evacuated from the interior of
the enclosure(s).
[0016] The source of electrical energy is preferably an electrical
signal generator that operates to generate either a low frequency
oscillatory current (e.g., less than 100 Hz, preferably between
about 0 to 60 Hz) or a direct current of between about 0.01 to 100
mA, more preferably between about 1-10 mA inclusive.
[0017] Other aspects, features, advantages, etc. will become
apparent to one skilled in the art when the description of the
invention herein is taken in conjunction with the accompanying
drawings.
INCORPORATION BY REFERENCE
[0018] Hereby, all issued patents, published patent applications,
and non-patent publications that are mentioned in this
specification are herein incorporated by reference in their
entirety for all purposes, to the same extent as if each individual
issued patent, published patent application, or non-patent
publication were specifically and individually indicated to be
incorporated by reference.
[0019] This application refers to the following patents and patent
applications, the entire disclosures of which are hereby
incorporated by reference for all purposes: Continuation-in-part of
U.S. patent application Ser. No. 12/394,972, filed Feb. 27, 2009,
which claims the benefit of provisional patent applications Ser.
Nos. 61/043,805 and 61/043,802, filed Apr. 10, 2007, and which is a
continuation-in-part of U.S. patent application Ser. No.
12/338,191, filed Dec. 18, 2008 the complete disclosures of which
are incorporated herein by reference for all purposes. This
application is also related to commonly assigned co-pending U.S.
patent Ser. Nos. 11/555,142, 11/555,170, 11/592,095, 11/591,340,
11/591,768, 11/754,522, 11/735,709 and 12/246,605 the complete
disclosures of which are incorporated herein by reference for all
purposes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] For the purposes of illustrating the various aspects of the
invention, there are shown in the drawings forms that are presently
preferred, it being understood, however, that the invention is not
limited by or to the precise arrangements and instrumentalities
shown.
[0021] FIG. 1 is a cross-sectional view of an electrode device in
accordance with one or more aspects of the present invention;
[0022] FIG. 2 is a schematic diagram of an electrical signal
generating system for use with the electrode device of FIG. 1;
and
[0023] FIGS. 3A and 3B illustrate a method of treating nerve
disorders in the brain according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] In the present invention, electrical energy is applied to
one or more electrodes in the presence of an electrically
conductive fluid to deliver an electrical signal to a patient. For
convenience, the remaining disclosure will be directed specifically
to the application of a low frequency oscillatory and/or weak
direct current to one or more target regions within a patient's
brain to treat the symptoms of certain disorders, such as epilepsy,
depression, Parkinson's disease, stroke and schizophrenia and/or
improve motor functions, improve working or declaratory memory
and/or memory consolidation. Suitable methods for performing such
transcranial current stimulation are described in W. Paulus,
"Transcranial Magnetic Stimulation and Transcranial Direct Current
Stimulation" (Supplements to Clinical Neurophysiology, volume 56)
and US Patent Application Publication No. 20080208287 to Palermo,
the complete disclosures of which are incorporated herein by
reference. However, it will be appreciated that the systems and
methods of the present invention can be applied equally well to
other tissues and nerves of the body, including but not limited to
cranial nerves, such as parasympathetic nerves, sympathetic nerves,
spinal nerves, facial nerves, vestibulocochlear nerves, enteric
nerves and the like.
[0025] With reference to FIG. 1, an exemplary device 100 for
delivering an electrical signal to a patient will now be described.
Device 100 is designed to be positioned in contact with an outer
skin surface of a patient at a location that (when activated)
achieves a therapeutic result. The device 100 includes an enclosure
for shielding the electrode(s) from direct contact with the
patient's skin. In the exemplary embodiment, the enclosure includes
a contact element 104 fluidly coupled to a fluid tube 106. An
electrode 110 is located within the interior of fluid tube 106. In
certain embodiments, electrode 110 will comprise a positive pole or
anode that typically causes an increase in firing of neurons
located close to the electrode 110. This up regulates these neurons
and increases their overall activity. In other embodiments,
electrode 110 will comprise a negative pole or cathode that
typically causes a decrease in firing of neurons or down regulation
of these neurons.
[0026] For convenience, only one device 100 has been illustrated.
However, it will be understood by those skilled in the art that
multiple devices 100 may be employed. For example, in certain
embodiments, the invention will utilize two devices 100 each having
an electrode 110 of opposite polarity (i.e., an anode and a
cathode) such that the electric current will pass from one of the
electrodes through the patient to the other electrode. In exemplary
embodiments, the invention includes both an anode and a cathode to
increase the activity of certain neurons while simultaneously
decreasing the activity of other neurons within the brain.
[0027] In other embodiments, one of the electrodes (either the
cathode or the anode) may act as a non-treatment electrode if up
regulation and/or down regulation of only one area of the brain is
desired. This can be accomplished by a variety of means known in
the art (i.e., electrodes with large surface areas act as suitable
non-treatment or return electrodes as they tend to have low current
densities). In such embodiments, the non-treatment or return
electrode may be positioned such that the electric current flows
from treatment electrode 110 through a specific target location in
the patient's brain (near treatment electrode 110) directly to the
non-treatment electrode. In other embodiments, the non-treatment or
return electrode may be positioned such that when applied to the
patient, the current passes out from electrode 110 in a
substantially radial pattern--in other words, the pattern of the
electro-magnetic field emanating from the electrode 110 is not
focused on any particular point, or small, localized region of the
patient's anatomy. This is preferably achieved by applying the
return electrode to an external portion of the patient, such as to
at least one of the upper-back, the chest, and/or the stomach
[0028] The contact element 104 preferably comprises an electrically
conductive material that will conform to the patient's head. By way
of example, contact element 104 may be substantially formed from a
biocompatible electrically conductive gel-like material, such as a
hydrogel. However, it will be recognized by those skilled in the
art that a variety of commercially available materials may be used
to carry out the present invention.
[0029] As shown in FIG. 1, fluid tube 106 includes an internal
lumen 116 coupled to a source of electrically conductive fluid (not
shown) and to contact element 104. At least one electrode 110 is
positioned within lumen 116 and coupled thereto (such as by a UV
curable adhesive, such as Dymax 204-CTH). Fluid tube 106 may be of
a standard type formed out of polyurethane with a length sufficient
to couple contact element 104 to the fluid source, and having an
inside diameter of about 5 mm (although other lengths, diameters,
and materials may be employed). Electrode 110 is preferably coupled
to internal lumen 116 about 1-20 cm away from contact element 104,
preferably about 3-8 cm. Spacing electrode 110 a suitable distance
from contact element 104 ensures that Faradic products from
electrode 110 do not pass through contact element 104 to the
patient's tissue. The greater the distance between contact element
104 and electrode 110, the longer it will take for these Faradic
products to move along lumen 116 to contact element 104.
[0030] Electrode 110 may be of a general annular or cylindrical
shape and may extend around the internal surface of passage 116.
Although there are a number of sizes and shapes that would suffice
to implement the electrode 110, by way of example, the at least one
electrode 110 may be between about 1.0-1.5 mm long (such as 1.27
mm) and may have an inside diameter of between about 2.5-2.75 mm
(such as 2.67 mm). A suitable electrode 110 may be formed from
Ag/AgCl or Pt-IR (90%/10%), although other materials or
combinations or materials may be used, such as platinum, tungsten,
gold, copper, palladium, silver or the like.
[0031] Those skilled in the art will also recognize that a variety
of different shapes and sizes of electrodes may be used. By way of
example only, electrode shapes according to the present invention
can include ball shapes, twizzle shapes, spring shapes, twisted
metal shapes, annular, solid tube shapes or the like.
Alternatively, the electrode(s) may comprise a plurality of
filaments, rigid or flexible brush electrode(s), coiled
electrode(s) or the like. Alternatively, the electrode may be
formed by the use of formed wire (e.g., by drawing round wire
through a shaping die) to form electrodes with a variety of
cross-sectional shapes, such as square, rectangular, L or V shaped,
or the like.
[0032] A conductor 122 extends through the lumen 116 of tube 106
and electrically connects to the electrode 110. By way of example,
the conductor 122 may be a solid silver wire of about 0.25 mm
diameter insulated with a PTFE material of about 0.33 mm diameter.
The diameter of the insulating material of the conductor 122 should
be less than the internal diameter of tube 106 such that fluid may
freely flow therein despite the presence of the conductor 122. The
conductor 122 may be laser welded to the electrode 110 using known
procedures.
[0033] A fluid, preferably a saline solution, passes into the tube
106 to substantially fill lumen 116 and provide a conductive
pathway from electrode 110 to contact element 104. This
configuration has several advantages over conventional electrode
configurations, such as: (i) the metal of the electrode 110 is not
too close to, and never comes in contact with, the patient's
tissue, which means that there is no concern about tissue necrosis
or excessive electric fields in the tissue; (ii) the electrode 110
may be used with direct current signal sources since any Faradic
Products (e.g. H+, OH-, H2O2) would not reach excessively high
concentrations at the tissue site; and (iii) the material of the
contact element 104 is preferably very soft and flexible such that
it gently conforms to the surrounding tissue.
[0034] The electrical properties of the electrode 110, the
conductive fluid, and the material of the contact element 104 are
preferably designed such that a resistance therethrough is no more
than about 1000 Ohms, preferably no more than 500 Ohms and more
preferably 200 Ohms or less. In an exemplary embodiment, the
impedance through the electrode 110, the fluid, and the material of
the contact element 104 should be no more than about 200 Ohms at
1000 Hz. The electrical properties of the fluid may be as important
as those of the electrode 110 in this regard. The electrically
conducting fluid should have a threshold conductivity to provide a
suitable conductive path between electrode 110 and contact element
104. The electrical conductivity of the fluid (in units of
milliSiemans per centimeter or mS/cm) will typically be between
about 1 mS/cm and 200 mS/cm and will usually be greater than 10
mS/cm, preferably will be greater than 20 mS/cm and more preferably
greater than 50 mS/cm. In one embodiment, the electrically
conductive fluid is isotonic saline, which has a conductivity of
about 17 mS/cm. Applicant has found that a more conductive fluid,
or one with a higher ionic concentration, will usually provide
optimal results. For example, a saline solution with higher levels
of sodium chloride than conventional saline (which is on the order
of about 0.9% sodium chloride) e.g., on the order of greater than
1% or between about 3% and 20%, may be desirable. A fluid of about
5% saline (e.g., approximately 100 mS/cm) is believed to work well,
although modifications to the concentration and the chemical
make-up of the fluid may be determined through simple
experimentation by skilled artisans. In certain embodiments, for
example, a buffered conductive solution may be used to further
mitigate contact between Faradic Products and the patient's
skin.
[0035] In an alternative embodiment, the electrode 110 may be
implemented via the fluid itself. Although a 5% saline solution
would have a relatively high resistance compared to a metal
electrode 110 implementation, those skilled in the art would
appreciate that higher conductivity fluid solutions may be employed
for such purposes or a larger diameter and/or shorter tube may be
utilized to increase the conductivity. Additionally or
alternatively, the conductor 122 may be implemented using the
conductive fluid; indeed, such fluid is within the lumen 116
anyway. Again, relatively high conductivity fluid would be
desirable.
[0036] With reference to FIG. 2, a complete system for using the
device 100 includes an electrical source 300, such as an impulse
generator. In this embodiment, source 300 is configured to apply
either a low frequency oscillatory current or a relatively weak
direct current to device 100. Source 300 operates to apply at least
one electrical signal to the conductors 122, 123 such that, when
the contact element 104 is positioned at the target region on the
patient, an electrical impulse passes through the electrode(s) 110,
111 to the anatomy of the patient in the vicinity of the target
region to achieve a therapeutic result.
[0037] In certain embodiments, electrical source is designed to
apply a low frequency oscillatory current through connectors 122,
123 to electrode(s) 110, 111 (e.g., less than 100 Hz, preferably
between about 0 to 60 Hz). In these embodiments, the source 300 may
be tailored for the treatment of a particular ailment and may
include an electrical impulse generator 310, a power source 320
coupled to the electrical impulse generator 310, and a control unit
330 in communication with the electrical impulse generator 310 and
the power source 320 (see FIG. 2). Electrodes 110, 111 provide
source and return paths for the at least one electrical signal
to/from the electrodes 110, 111. The control unit 330 may control
the electrical impulse generator 310 for generation of the signal
suitable for amelioration of the ailment when the signal is applied
via the electrodes 110, 111 to the device 100. For example, the
signal may have a pulse duration of between about 10-1000 us and an
amplitude of between about 1-20 volts.
[0038] The control unit 330 may control the electrical impulse
generator 310 for generation of the signal suitable for
amelioration of the ailment when the signal is applied via the
connectors 122, 123 to the electrodes 110, 111. It is noted that
source 300 may be referred to by its function as a pulse
generator.
[0039] In other embodiments, electrical source 300 is a direct
current source for applying a direct current through lead conductor
122 to electrode(s) 110, 111. The direct current is preferably
between about 0.1 mA to about 100 mA, more preferably between about
1-10 mA inclusive.
[0040] In a preferred embodiment of the present invention, a device
for mild brain stimulation is disclosed. Recent studies have
indicated that motor skill learning may be enhanced by applying a
mild electrical current to a motor control area of the brain (see
study conducted by the National Institute of Health and presented
in the Jan. 20, 2009 early online edition of the Proceedings of the
National Academy of Sciences). Patients receiving this current were
significantly better able to learn and perform a complex motor task
than those in the control groups. The findings could hold promise
for enhancing rehabilitation for people with traumatic brain
injury, stroke and other conditions. Motor skills which are used
for activities from typing to driving, to sports, require practice
and learning over a prolonged period of time. During practice, the
brain encodes information about how to perform the task, but even
during periods of rest, the brain is still working to strengthen
the memory of doing the task. This process is known as
consolidation. During practice, one group received 20 minutes of
transcranial direct current stimulation (tDCS), which involves mild
electrical stimulation applied through surface electrodes on the
head, and works by modulating the excitability of cells in the
brain's outermost layers, such as the primary motor cortex.
[0041] Transcranial direct current stimulation is being studied for
treatment of a number of conditions, such as improving motor
performance in healthy people, accelerating recovery from major
stroke (in combination with occupational therapy) and the treatment
of acute pain, epilepsy, fibromyalgia, schizophrenia and major
depression. Schizophrenics often have what are called negative
symptoms. Negative symptoms include apathy, poor attention, poor
grooming habits and poor motivation. These symptoms have been
associated with under activity of the frontal lobes, particularly a
brain area called the left dorsolateral prefrontal cortex (LDPFC).
Positive schizophrenic symptoms such as hallucinations may be
associated with over activity in different brain areas, like the
temporal cortex. Thus, tDCS may be able to up regulate activity in
the left dorsolateral prefrontal cortex while simultaneously
decreasing activity in the temporal cortex. This could have a
substantial impact on a range of schizophrenic symptoms. For
depression, tDCS may be able to up regulate activity in the left
dorsolateral prefrontal cortex while simultaneously decreasing
activity in the right dorsolateral prefrontal cortex. This will
likely have a more robust antidepressant effect.
[0042] Transcranial direct current stimulation typically involves
the application of weak electrical currents (e.g., 0.5-10 mA,
preferably about 1-2 mA) to modulate the activity of targeted
neurons in the brain. Several generations of neurophysiologic
experiments have shown that neurons respond to static (DC)
electrical fields by altering their firing rates. Firing increases
when the positive pole or electrode (anode) is located near the
cell body or dendrites and decrease when the field is reversed.
However, when the electrodes are placed on the scalp, the current
density produced in the brain is exceedingly small, changing
membrane potentials only by a fraction of a millivolt. tDCS
typically only influences the area of the brain directly underneath
the electrode that is close to the skull and thus is more selective
than other methods of brain stimulation. Transcranial direct
current stimulation is not "stimulation" in the same sense as
transcranial magnetic stimulation or the stimulation of the brain
and nerves with conventional techniques. It does not appear to
cause nerve cell firing on its own and does not produce discrete
effects such as the muscle twitches associated with classical
stimulation.
[0043] Transcranial direct current stimulation has also been shown
to modulate excitability in the motor, visual, and prefrontal
cortex. Periods rich in slow-wave sleep (SWS) not only facilitate
the consolidation of declarative memories, but in humans, SWS is
also accompanied by a pronounced endogenous transcortical DC
potential shift of negative polarity over frontocortical areas. To
induce widespread extracellular negative DC potentials, it has been
shown that application of anodal tDCS (0.26 mA/cm2) repeatedly
(over 30 min) bilaterally at frontocortical electrode sites during
a retention period rich in SWS can result in increased retention of
declarative memories (word pairs) and also nondeclarative memories
(mirror tracing skills) learned previously. It has been speculated
that the effects of tDCS involve enhanced generation of slow
oscillatory EEG activity considered to facilitate processes of
neuronal plasticity. Shifts in extracellular ionic concentration in
frontocortical tissue (expressed as negative DC potentials during
SWS) may facilitate sleep-dependent consolidation of declarative
memories.
[0044] One of the limitations of current tDCS is that the direct
current can only be applied for a limited period of time and at a
limited power or voltage because the electrodes will begin to
damage the tissue they are in contact with. The present invention
solves this problem by providing an electrode device designed to
space the electrode from the patient's tissue.
[0045] Referring now to FIGS. 3A and 3B, a general method for
treating brain disorders or for improving motor and/or memory
functions will now be described. One or more target regions 400 of
the brain 402 are first located by the physician. The target
regions 400 will of course depend on the desired treatment as
described above. The target regions 400 may be identified with
reference to anatomical features of the patient, such as the
patient's nose or ears. In other embodiments, the target regions
400 may be indentified with reference to fiducials 404 positioned
in the patient's skull 406, as shown in FIG. 3A. The location of
the fiducials 404 can appear on the image (or other display formats
known in the art) used to present the neural activity information
and identify the desired target regions 400.
[0046] Referring now to FIG. 3B, an exemplary stimulation device
410 is shown having two contact elements 412, 414 (such as a
hydrogel) configured for placement on the outer surface of the
patient's skull 406. Fluid tubes 416, 418 extend from contact
elements 412, 414, respectively, and are coupled to an electrically
conductive fluid source (not shown). In this embodiment,
stimulation device 410 further includes two electrodes 424, 426 of
opposite polarity positioned within the interior of fluid tubes
416, 418. In the exemplary embodiment, fluid tube 416 houses the
anode and fluid tube 418 houses a cathode, although many other
configurations are possible as discussed above. Internal electrical
leads (not shown) couple electrodes 424, 426 to a source of
electrical energy (not shown). Fluid tubes 416, 418 may also
include a vacuum source (not shown) for periodically aspirating the
conductive fluid.
[0047] In use, contact elements 412, 414 are positioned on the
patient's skull 406 adjacent or near target regions 400 in the
brain 402. In the exemplary embodiment, contact element 412 with
the anode is placed adjacent a target region that is underactive
(for example, the left dorsolateral prefrontal cortex or LDPFC in a
patient suffering from schizophrenia) and contact element 414 with
the cathode is placed adjacent a target region that is overactive
(e.g., the right dorsolateral prefrontal cortex or RDPFC). An
electrically conductive fluid is then delivered through fluid tubes
416, 418 to electrically couple electrodes 424, 426 to contact
elements 412, 414. Contact elements 412, 414 may be attached to
skull 406 in any suitable manner known to those in the art.
[0048] An electrical current is then applied to the electrodes,
which flows from the electrodes 424, 426 through the conductive
fluid and contact elements 412, 414 into the target regions 400 of
the patient's brain 402. The current will increase the activity of
nerves adjacent to the anode, while decreasing the activity of
nerves adjacent to the cathode. Since the electrodes do not
directly contact the tissue of the patient, the present invention
reduces the potential for collateral tissue damage or necrosis
and/or excessive electric fields in the tissue. In addition, the
enclosures physically shield the electrode from the tissue of the
patient's head, which substantially inhibits Faradic products
(e.g., H+, OH-, H2O2) of the electrodes from contacting this
tissue. Thus, the direct current can be applied to the patient's
brain without the danger of such Faradic products reaching
excessively high concentrations at the tissue site, allowing for a
longer treatment time and/or higher current levels than is
currently considered safe for the patient.
[0049] In yet another embodiment of the present invention, the
electrode device may be used to amplify motor memory and/or enhance
declaratory memory by delivering current oscillations in the REM
bandwidth during REM sleep. In this embodiment, an oscillatory
current is delivered through an electrode device as described
above. The frequency of the oscillatory current will vary depending
on the desired treatment. For example, to amplify motor memory, the
preferred frequency range is between about 20-60 Hz. To enhance
declarative memory, the preferred frequency range is between about
0-4 Hz.
[0050] In other embodiments, the invention may be used to disrupt
epileptic seizures by entraining circuits at lower frequencies than
supported by the epileptic neural circuit. The device may be used
to desynchronize brain activity, as in the case of an epileptic
patient where oversynchronization has occurred.
[0051] Although the invention herein has been described with
reference to particular embodiments, it is to be understood that
these embodiments are merely illustrative of the principles and
applications of the present invention. It is therefore to be
understood that numerous modifications may be made to the
illustrative embodiments and that other arrangements may be devised
without departing from the spirit and scope of the present
invention as defined by the appended claims.
* * * * *