Transcranial direct current stimulation
Encyclopedia
Transcranial direct current stimulation (tDCS) is a form of neurostimulation
which uses constant, low current delivered directly to the brain area of interest via small electrodes. Currently, tDCS is used as therapy for certain psychological disorders such as anxiety disorder
s and depression, as well as a tool for motor rehabilitation in stroke
patients.
to stimulate the area of interest, has been around for over 100 years. There were a number of rudimentary experiments completed before the 19th century using this technique that tested animal and human electricity. Luigi Galvani
and Alessandro Volta
were two such researchers that utilized the technology of tDCS in their explorations of the source of animal cell electricity. It was due to these initial studies that tDCS was first brought into the clinical scene. In 1804, Aldini started a study in which he used the technique of direct current stimulation and was successful in improving the mood of melancholy patients. Unfortunately, this discovery did not receive much attention and was forgotten in the light of other types of neurostimulation
. When electroshock therapy was developed in the 1930s and was found to be a relatively effective treatment against depression, therapy using tDCS was abandoned.
It wasn’t until recently that tDCS was rediscovered for a third time. This time, the rediscovery was fueled by an increase of interest and understanding of basic brain functioning as well as new brain stimulation and brain imaging techniques such as TMS
and fMRI. Now, Transcranial direct current stimulation is beginning to be used more frequently as a brain stimulation technique because safety protocol has shown that tDCS is extremely safe for human use.
through the electrode
s. When these electrodes are placed in the region of interest, the current induces intracerebral current flow. This current flow then either increases or decreases the neuronal excitability in the specific area being stimulated based on which type of stimulation is being used. This change of neuronal excitability leads to alteration of brain function, which can be used in various therapies as well as to provide more information about the functioning of the human brain.
electrode to the cathodal
electrode, creating a circuit
. The device that delivers the current has controls that set the current as well as the duration of stimulation.
. The careful placement of the electrodes is crucial to successful tDCS technique. The electrode pads come in various sizes with benefits to each size. A smaller sized electrode achieves a more focused stimulation of a site while a larger electrode ensures that the entirety of the region of interest is being stimulated. If the electrode is placed incorrectly, a different site or more sites than intended may be stimulated resulting in faulty results. One of the electrodes is placed over the region of interest and the other electrode, the reference electrode, is placed in another location in order to complete the circuit
. This reference electrode is usually placed on the neck or shoulder of the opposite side of the body than the region of interest. Since the region of interest may be small, it is often useful to locate this region before placing the electrode by using a brain imaging technique such as fMRI or PET
. Once the electrodes are placed correctly, the stimulation can be started. Many devices have a built-in capability that allows the current to be “ramped up” or increased slowly until the necessary current is reached. This decreases the amount of stimulation effects felt by the person receiving the tDCS. After the stimulation has been started, the current will continue for the amount of time set on the device and then will automatically be shut off.
, cathodal
, and sham. The anodal stimulation is positive stimulation that increases the neuronal excitability of the area being stimulated. Cathodal stimulation decreases the neuronal excitability of the area being stimulated. An example of how cathodal stimulation could be used is as a therapy for a psychological disorder caused by the hyper-activity of a particular area of the brain. Cathodal stimulation would decrease the neuronal excitability to reach a more stable level of activity. Sham stimulation is important because it is the control stimulation. This stimulation emits a brief current but then remains off for the remainder of the stimulation time. With sham stimulation, the person receiving the tDCS does not know that they are not receiving prolonged stimulation; this provides a control condition for experiments, which can be double-blinded. Without this type of stimulation, the effects of the positive or negative stimulation could not be proven.
or hyperpolarize. When positive stimulation is delivered, the current causes a depolarization of the resting membrane potential, which increases neuronal excitability and allows for more spontaneous cell
firing. When negative stimulation is delivered, the current causes a hyperpolarization of the resting membrane potential. This decreases neuron excitability due to the decreased spontaneous cell firing.
Neuroplasticity
refers to the ability of the brain to change throughout life based on experiences. The way that transcranial direct current stimulation functions could be due to the plasticity concepts of long term potentiation and long term depression since the two share some basic similarities. Long term potentiation is the strengthening between two neuron
s while long term depression is the weakening between two neurons. These effects are achieved mainly through an alteration of synaptic transmission ability. LTP enhances transmission and LTD hinders transmission. Likewise, tDCS stimulation involves the alteration of synaptic transmission ability through modifications of intracellular
cAMP
and calcium
levels. Also, both LTP, LTD, and the effects of tDCS are protein synthesis dependent. It is for these reasons that LTP and LTD are proposed mechanisms of the function of tDCS.
(TMS). This technique of brain stimulation utilizes a electric coil held above the region of interest on the scalp that uses rapidly changing magnetic fields to induce small electrical currents in the brain. There are two types of TMS: repetitive TMS and single pulse TMS. Both are used in research therapy but effects lasting longer than the stimulation period are only observed in repetitive TMS. Similar to tDCS, an increase or decrease in neuronal activity can be achieved using this technique, but the method of how this is induced is very different. Transcranial direct current stimulation has the two different directions of current that cause the different effects. Increased neuronal activity is induced in repetitive TMS by using a higher frequency and decreased neuronal activity is induced by using a lower frequency.
Both TMS and tDCS are painless and considered safe for human use. Transcranial magnetic stimulation causes the neuron’s
action potential
s to fire, resulting in a stronger effect. This larger effect could be beneficial in both therapy and research. Since tDCS only causes increased spontaneous cell firing, it does not have as big as an effect. One benefit of tDCS when compared to TMS is that due to the smaller effect, there is a much smaller chance of causing seizure
s in the person receiving the stimulation.
and usually 1 mA or less is used. The device itself has a maximum current setting that while above what is suggested to use, it is still within a range in which no harm is done to the person receiving the stimulation.
Studies have been completed to determine the current density at which overt brain damage
occurs in rats. It was found that in cathodal
stimulation, a current density
of 142.9 A/m2 delivering a charge density
of 52400 C/m2 or higher caused a brain lesion
in the rat. This is over two orders of magnitude from what is currently being used.
There is no strict limitation on the duration of stimulation set at this point but a stimulation time of 20 minutes is considered the ideal time. The longer the stimulation duration, the longer the observed effects of the stimulation persist once the stimulation has ended. A stimulation length of 10 minutes results in observed effects lasting for up to an hour.
It is generally encouraged to wait at least 48 hours to a week before repeating the stimulation. Also, it is advised to warn the person receiving the stimulation of the possible after effects of the tDCS stimulation.
at the start of stimulation, nausea
, headache
, dizziness, and itching under the electrode. Nausea most commonly occurs when the electrodes are placed above the mastoid, which are used for stimulation of the vestibular system
. A phosphene is a brief flash of light and this effect can occur if an electrode is placed near to the eye. A recent study of over 500 subjects using the currently accepted protocol reported only a slight skin irritation and a phosphene as side effects.
There are several ways to reduce the skin irritation felt during stimulation. One of the most important methods of preventing skin irritation is by preparing the electrodes with saline solution and the skin with electrode cream thoroughly. Also, ramping up the current can reduce the irritation. This is done by slowly increasing the current until the desired current is reached.
s, such as people with epilepsy
. Although seizures do not seem to be a risk for healthy individuals, those with a tendency towards seizures may react differently. As more is discovered about the use of tDCS, the safety standards may change, making it important to remain familiar with the most currently updated safety protocol.
, fibromyalgia
, and post-stroke
motor deficits. In a recent study, stroke patients with speech difficulties displayed great improvement through a tDCS based therapy, with the improvement lasting past the one week retest. Stimulation therapy could also be developed into effective therapy for various psychological disorders such as depression, anxiety disorder
s, and schizophrenia
.
Neurostimulation
Neurostimulation involves modulation of the nervous system and electrically activate neurons in the body. The activation of neural elements in a part of the nervous system can be effectively facilitated by stimulation. Micro-electrodes are utilized to interface with excitable tissue in order to...
which uses constant, low current delivered directly to the brain area of interest via small electrodes. Currently, tDCS is used as therapy for certain psychological disorders such as anxiety disorder
Anxiety disorder
Anxiety disorder is a blanket term covering several different forms of abnormal and pathological fear and anxiety. Conditions now considered anxiety disorders only came under the aegis of psychiatry at the end of the 19th century. Gelder, Mayou & Geddes explains that anxiety disorders are...
s and depression, as well as a tool for motor rehabilitation in stroke
Stroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...
patients.
Discovery
The basic design of tDCS, using direct currentDirect current
Direct current is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through...
to stimulate the area of interest, has been around for over 100 years. There were a number of rudimentary experiments completed before the 19th century using this technique that tested animal and human electricity. Luigi Galvani
Luigi Galvani
Luigi Aloisio Galvani was an Italian physician and physicist who lived and died in Bologna. In 1791, he discovered that the muscles of dead frogs legs twitched when struck by a spark...
and Alessandro Volta
Alessandro Volta
Count Alessandro Giuseppe Antonio Anastasio Gerolamo Umberto Volta was a Lombard physicist known especially for the invention of the battery in 1800.-Early life and works:...
were two such researchers that utilized the technology of tDCS in their explorations of the source of animal cell electricity. It was due to these initial studies that tDCS was first brought into the clinical scene. In 1804, Aldini started a study in which he used the technique of direct current stimulation and was successful in improving the mood of melancholy patients. Unfortunately, this discovery did not receive much attention and was forgotten in the light of other types of neurostimulation
Neurostimulation
Neurostimulation involves modulation of the nervous system and electrically activate neurons in the body. The activation of neural elements in a part of the nervous system can be effectively facilitated by stimulation. Micro-electrodes are utilized to interface with excitable tissue in order to...
. When electroshock therapy was developed in the 1930s and was found to be a relatively effective treatment against depression, therapy using tDCS was abandoned.
Transition into modern scientific research
There was a brief rise of interest in transcranial direct current stimulation in the 1960s when studies by the researcher Albert proved that the stimulation could affect brain function by changing the cortical excitability. He also discovered that positive and negative stimulation had different effects on the cortical excitability. Although these findings were important in the use of tDCS in therapy, research in this area was again dropped as drug therapy proved to be a more effective and simple method of therapy.It wasn’t until recently that tDCS was rediscovered for a third time. This time, the rediscovery was fueled by an increase of interest and understanding of basic brain functioning as well as new brain stimulation and brain imaging techniques such as TMS
TMS
- Organizations :* The Minerals, Metals & Materials Society, a professional organization for materials scientists and engineers* Texas Memory Systems, a manufacturer of solid-state drives...
and fMRI. Now, Transcranial direct current stimulation is beginning to be used more frequently as a brain stimulation technique because safety protocol has shown that tDCS is extremely safe for human use.
How it works
Transcranial direct current stimulation works by sending constant, low direct currentDirect current
Direct current is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through...
through the electrode
Electrode
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit...
s. When these electrodes are placed in the region of interest, the current induces intracerebral current flow. This current flow then either increases or decreases the neuronal excitability in the specific area being stimulated based on which type of stimulation is being used. This change of neuronal excitability leads to alteration of brain function, which can be used in various therapies as well as to provide more information about the functioning of the human brain.
Parts
Transcranial direct current stimulation is a relatively simple technique and contains only a few parts. These include two electrodes and a battery powered device that delivers constant current. Control software can also be used in experiments that require multiple sessions with differing stimulation types such that neither the person receiving the stimulation nor the person administering the stimulation knows which type is currently being administered. Each device has an anodal electrode and a cathodal electrode. The anodal electrode is the positively charged electrode and the cathodal electrode is the negatively charged electrode. The current flows from the anodalAnode
An anode is an electrode through which electric current flows into a polarized electrical device. Mnemonic: ACID ....
electrode to the cathodal
Cathode
A cathode is an electrode through which electric current flows out of a polarized electrical device. Mnemonic: CCD .Cathode polarity is not always negative...
electrode, creating a circuit
Electrical network
An electrical network is an interconnection of electrical elements such as resistors, inductors, capacitors, transmission lines, voltage sources, current sources and switches. An electrical circuit is a special type of network, one that has a closed loop giving a return path for the current...
. The device that delivers the current has controls that set the current as well as the duration of stimulation.
Set up
To set up the tDCS device, the electrodes and the skin need to be prepared. This ensures a strong connection between the skin and the electrodeElectrode
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit...
. The careful placement of the electrodes is crucial to successful tDCS technique. The electrode pads come in various sizes with benefits to each size. A smaller sized electrode achieves a more focused stimulation of a site while a larger electrode ensures that the entirety of the region of interest is being stimulated. If the electrode is placed incorrectly, a different site or more sites than intended may be stimulated resulting in faulty results. One of the electrodes is placed over the region of interest and the other electrode, the reference electrode, is placed in another location in order to complete the circuit
Electrical network
An electrical network is an interconnection of electrical elements such as resistors, inductors, capacitors, transmission lines, voltage sources, current sources and switches. An electrical circuit is a special type of network, one that has a closed loop giving a return path for the current...
. This reference electrode is usually placed on the neck or shoulder of the opposite side of the body than the region of interest. Since the region of interest may be small, it is often useful to locate this region before placing the electrode by using a brain imaging technique such as fMRI or PET
Positron emission tomography
Positron emission tomography is nuclear medicine imaging technique that produces a three-dimensional image or picture of functional processes in the body. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide , which is introduced into the body on a...
. Once the electrodes are placed correctly, the stimulation can be started. Many devices have a built-in capability that allows the current to be “ramped up” or increased slowly until the necessary current is reached. This decreases the amount of stimulation effects felt by the person receiving the tDCS. After the stimulation has been started, the current will continue for the amount of time set on the device and then will automatically be shut off.
Types of stimulation
There are three different types of stimulation: anodalAnode
An anode is an electrode through which electric current flows into a polarized electrical device. Mnemonic: ACID ....
, cathodal
Cathode
A cathode is an electrode through which electric current flows out of a polarized electrical device. Mnemonic: CCD .Cathode polarity is not always negative...
, and sham. The anodal stimulation is positive stimulation that increases the neuronal excitability of the area being stimulated. Cathodal stimulation decreases the neuronal excitability of the area being stimulated. An example of how cathodal stimulation could be used is as a therapy for a psychological disorder caused by the hyper-activity of a particular area of the brain. Cathodal stimulation would decrease the neuronal excitability to reach a more stable level of activity. Sham stimulation is important because it is the control stimulation. This stimulation emits a brief current but then remains off for the remainder of the stimulation time. With sham stimulation, the person receiving the tDCS does not know that they are not receiving prolonged stimulation; this provides a control condition for experiments, which can be double-blinded. Without this type of stimulation, the effects of the positive or negative stimulation could not be proven.
Effects on brain
One of the most important aspects of tDCS is its ability to achieve cortical changes even after the stimulation is ended. The duration of this change depends on the length of stimulation as well as the intensity of stimulation. The effects of stimulation increase as the duration of stimulation increases or the strength of the current increases. The way that the stimulation changes brain function is either by causing the neuron’s resting membrane potential to depolarizeDepolarization
In biology, depolarization is a change in a cell's membrane potential, making it more positive, or less negative. In neurons and some other cells, a large enough depolarization may result in an action potential...
or hyperpolarize. When positive stimulation is delivered, the current causes a depolarization of the resting membrane potential, which increases neuronal excitability and allows for more spontaneous cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
firing. When negative stimulation is delivered, the current causes a hyperpolarization of the resting membrane potential. This decreases neuron excitability due to the decreased spontaneous cell firing.
Neuroplasticity
Neuroplasticity
Neuroplasticity is a non-specific neuroscience term referring to the ability of the brain and nervous system in all species to change structurally and functionally as a result of input from the environment. Plasticity occurs on a variety of levels, ranging from cellular changes involved in...
refers to the ability of the brain to change throughout life based on experiences. The way that transcranial direct current stimulation functions could be due to the plasticity concepts of long term potentiation and long term depression since the two share some basic similarities. Long term potentiation is the strengthening between two neuron
Neuron
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...
s while long term depression is the weakening between two neurons. These effects are achieved mainly through an alteration of synaptic transmission ability. LTP enhances transmission and LTD hinders transmission. Likewise, tDCS stimulation involves the alteration of synaptic transmission ability through modifications of intracellular
Intracellular
Not to be confused with intercellular, meaning "between cells".In cell biology, molecular biology and related fields, the word intracellular means "inside the cell".It is used in contrast to extracellular...
cAMP
Cyclic adenosine monophosphate
Cyclic adenosine monophosphate is a second messenger important in many biological processes...
and calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
levels. Also, both LTP, LTD, and the effects of tDCS are protein synthesis dependent. It is for these reasons that LTP and LTD are proposed mechanisms of the function of tDCS.
TMS
Transcranial direct current stimulation is a relatively new method of stimulating the brain. While this method is gaining interest, the most commonly used method of brain stimulation is transcranial magnetic stimulationTranscranial magnetic stimulation
Transcranial magnetic stimulation is a noninvasive method to cause depolarization or hyperpolarization in the neurons of the brain...
(TMS). This technique of brain stimulation utilizes a electric coil held above the region of interest on the scalp that uses rapidly changing magnetic fields to induce small electrical currents in the brain. There are two types of TMS: repetitive TMS and single pulse TMS. Both are used in research therapy but effects lasting longer than the stimulation period are only observed in repetitive TMS. Similar to tDCS, an increase or decrease in neuronal activity can be achieved using this technique, but the method of how this is induced is very different. Transcranial direct current stimulation has the two different directions of current that cause the different effects. Increased neuronal activity is induced in repetitive TMS by using a higher frequency and decreased neuronal activity is induced by using a lower frequency.
Both TMS and tDCS are painless and considered safe for human use. Transcranial magnetic stimulation causes the neuron’s
Neuron
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...
action potential
Action potential
In physiology, an action potential is a short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a consistent trajectory. Action potentials occur in several types of animal cells, called excitable cells, which include neurons, muscle cells, and...
s to fire, resulting in a stronger effect. This larger effect could be beneficial in both therapy and research. Since tDCS only causes increased spontaneous cell firing, it does not have as big as an effect. One benefit of tDCS when compared to TMS is that due to the smaller effect, there is a much smaller chance of causing seizure
Seizure
An epileptic seizure, occasionally referred to as a fit, is defined as a transient symptom of "abnormal excessive or synchronous neuronal activity in the brain". The outward effect can be as dramatic as a wild thrashing movement or as mild as a brief loss of awareness...
s in the person receiving the stimulation.
Other types of stimulation
One other technique of electrical stimulation that has been used is called transcranial electrical stimulation, or TES. TES also functions by inducing neuronal change via electrical currents. TES unlike tDCS causes the resting neurons to fire and can be painful to the person receiving the stimulation, so this method is no longer frequently used.Safety
When applied following established safety protocols, transcranial direct current stimulation is widely regarded as a safe method of brain stimulation, causing no apparent short-term harm. Safety protocols limit the current, duration, and frequency of stimulation, thereby limiting the effects and riskSafety protocol
There has been much work done in the last 10 years to develop a safety protocol for administering transcranial direct current stimulation. Many studies have been conducted to determine the optimal time of stimulation and current used as well as steps to take in order to reduce or eliminate the side effects felt by the person receiving the stimulation. These standards are still not entirely set and continue to expand as more research is done. Currently, the accepted maximum current for human use is 2 mAAmpere
The ampere , often shortened to amp, is the SI unit of electric current and is one of the seven SI base units. It is named after André-Marie Ampère , French mathematician and physicist, considered the father of electrodynamics...
and usually 1 mA or less is used. The device itself has a maximum current setting that while above what is suggested to use, it is still within a range in which no harm is done to the person receiving the stimulation.
Studies have been completed to determine the current density at which overt brain damage
Brain damage
"Brain damage" or "brain injury" is the destruction or degeneration of brain cells. Brain injuries occur due to a wide range of internal and external factors...
occurs in rats. It was found that in cathodal
Cathode
A cathode is an electrode through which electric current flows out of a polarized electrical device. Mnemonic: CCD .Cathode polarity is not always negative...
stimulation, a current density
Current density
Current density is a measure of the density of flow of a conserved charge. Usually the charge is the electric charge, in which case the associated current density is the electric current per unit area of cross section, but the term current density can also be applied to other conserved...
of 142.9 A/m2 delivering a charge density
Charge density
The linear, surface, or volume charge density is the amount of electric charge in a line, surface, or volume, respectively. It is measured in coulombs per meter , square meter , or cubic meter , respectively, and represented by the lowercase Greek letter Rho . Since there are positive as well as...
of 52400 C/m2 or higher caused a brain lesion
Lesion
A lesion is any abnormality in the tissue of an organism , usually caused by disease or trauma. Lesion is derived from the Latin word laesio which means injury.- Types :...
in the rat. This is over two orders of magnitude from what is currently being used.
There is no strict limitation on the duration of stimulation set at this point but a stimulation time of 20 minutes is considered the ideal time. The longer the stimulation duration, the longer the observed effects of the stimulation persist once the stimulation has ended. A stimulation length of 10 minutes results in observed effects lasting for up to an hour.
It is generally encouraged to wait at least 48 hours to a week before repeating the stimulation. Also, it is advised to warn the person receiving the stimulation of the possible after effects of the tDCS stimulation.
Side effects of stimulation
There are a few minor side effects that can be felt by the person while receiving the stimulation, and most of these can be controlled by correct set up of the device. These side effects include skin irritation, a phosphenePhosphene
A phosphene is a phenomenon characterized by the experience of seeing light without light actually entering the eye. The word phosphene comes from the Greek words phos and phainein...
at the start of stimulation, nausea
Nausea
Nausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...
, headache
Headache
A headache or cephalalgia is pain anywhere in the region of the head or neck. It can be a symptom of a number of different conditions of the head and neck. The brain tissue itself is not sensitive to pain because it lacks pain receptors. Rather, the pain is caused by disturbance of the...
, dizziness, and itching under the electrode. Nausea most commonly occurs when the electrodes are placed above the mastoid, which are used for stimulation of the vestibular system
Vestibular system
The vestibular system, which contributes to balance in most mammals and to the sense of spatial orientation, is the sensory system that provides the leading contribution about movement and sense of balance. Together with the cochlea, a part of the auditory system, it constitutes the labyrinth of...
. A phosphene is a brief flash of light and this effect can occur if an electrode is placed near to the eye. A recent study of over 500 subjects using the currently accepted protocol reported only a slight skin irritation and a phosphene as side effects.
There are several ways to reduce the skin irritation felt during stimulation. One of the most important methods of preventing skin irritation is by preparing the electrodes with saline solution and the skin with electrode cream thoroughly. Also, ramping up the current can reduce the irritation. This is done by slowly increasing the current until the desired current is reached.
Risks
There are no known risks of tDCS at this time, but since this technique of stimulation is still being explored, safety precautions should be kept. The set protocols must be followed in ensure correct use of the device. Also, it is not advised to administer this stimulation to people susceptible to seizureSeizure
An epileptic seizure, occasionally referred to as a fit, is defined as a transient symptom of "abnormal excessive or synchronous neuronal activity in the brain". The outward effect can be as dramatic as a wild thrashing movement or as mild as a brief loss of awareness...
s, such as people with epilepsy
Epilepsy
Epilepsy is a common chronic neurological disorder characterized by seizures. These seizures are transient signs and/or symptoms of abnormal, excessive or hypersynchronous neuronal activity in the brain.About 50 million people worldwide have epilepsy, and nearly two out of every three new cases...
. Although seizures do not seem to be a risk for healthy individuals, those with a tendency towards seizures may react differently. As more is discovered about the use of tDCS, the safety standards may change, making it important to remain familiar with the most currently updated safety protocol.
Uses
There are many uses of transcranial direct current stimulation and as more research is done understanding and improving this technique, this list will continue to grow.Clinical
Clinical therapy using tDCS may be the most promising application of this technique. There have been therapeutic effects shown in clinical trials involving Parkinson’s disease, tinnitusTinnitus
Tinnitus |ringing]]") is the perception of sound within the human ear in the absence of corresponding external sound.Tinnitus is not a disease, but a symptom that can result from a wide range of underlying causes: abnormally loud sounds in the ear canal for even the briefest period , ear...
, fibromyalgia
Fibromyalgia
Fibromyalgia is a medical disorder characterized by chronic widespread pain and allodynia, a heightened and painful response to pressure. It is an example of a diagnosis of exclusion...
, and post-stroke
Stroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...
motor deficits. In a recent study, stroke patients with speech difficulties displayed great improvement through a tDCS based therapy, with the improvement lasting past the one week retest. Stimulation therapy could also be developed into effective therapy for various psychological disorders such as depression, anxiety disorder
Anxiety disorder
Anxiety disorder is a blanket term covering several different forms of abnormal and pathological fear and anxiety. Conditions now considered anxiety disorders only came under the aegis of psychiatry at the end of the 19th century. Gelder, Mayou & Geddes explains that anxiety disorders are...
s, and schizophrenia
Schizophrenia
Schizophrenia is a mental disorder characterized by a disintegration of thought processes and of emotional responsiveness. It most commonly manifests itself as auditory hallucinations, paranoid or bizarre delusions, or disorganized speech and thinking, and it is accompanied by significant social...
.