Electrical brain stimulation (EBS), also referred to as focal brain stimulation (FBS), is a form of

electrotherapy Electrotherapy is the use of electrical energy as a medical treatment. In medicine, the term ''electrotherapy'' can apply to a variety of treatments, including the use of electrical devices such as deep brain stimulators for neurological dise ...

used as a technique in

research Research is "creativity, creative and systematic work undertaken to increase the stock of knowledge". It involves the collection, organization and analysis of evidence to increase understanding of a topic, characterized by a particular att ...

and

clinic A clinic (or outpatient clinic or ambulatory care clinic) is a health facility that is primarily focused on the care of outpatients. Clinics can be privately operated or publicly managed and funded. They typically cover the primary care needs ...

neurobiology Neuroscience is the scientific study of the nervous system (the brain, spinal cord, and peripheral nervous system), its functions and disorders. It is a multidisciplinary science that combines physiology, anatomy, molecular biology, development ...

to stimulate a

neuron A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous tissue in all animals except sponges and placozoa. N ...

neural network A neural network is a network or circuit of biological neurons, or, in a modern sense, an artificial neural network, composed of artificial neurons or nodes. Thus, a neural network is either a biological neural network, made up of biological ...

in the

brain A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a v ...

through the direct or indirect

excitation Excitation, excite, exciting, or excitement may refer to: * Excitation (magnetic), provided with an electrical generator or alternator * Excite Ballpark, located in San Jose, California * Excite (web portal), web portal owned by IAC * Electron exc ...

of its

cell membrane The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment ( ...

by using an

electric current An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The moving pa ...

. EBS is used for research or for

therapeutic A therapy or medical treatment (often abbreviated tx, Tx, or Tx) is the attempted remediation of a health problem, usually following a medical diagnosis. As a rule, each therapy has indications and contraindications. There are many different ...

purposes.

History

Electrical brain stimulation was first used in the first half of the 19th century by pioneering researchers such as

Luigi Rolando Luigi Rolando (16 June 1773, Turin – 20 April 1831, Turin) was an Italian anatomist known for his pioneering research in brain localization of function. He studied medicine in Turin, later continuing his education in Florence, where he studied ...

(1773–1831) and

Pierre Flourens Marie Jean Pierre Flourens (13 April 1794 – 6 December 1867), father of Gustave Flourens, was a French physiologist, the founder of experimental brain science, and a pioneer in anesthesia. Biography Flourens was born at Maureilhan, near Bézi ...

(1794–1867), to study the

brain localization of function The lateralization of brain function is the tendency for some neural functions or cognitive processes to be specialized to one side of the brain or the other. The median longitudinal fissure separates the human brain into two distinct cerebral ...

, following the discovery by Italian physician

Luigi Galvani Luigi Galvani (, also ; ; la, Aloysius Galvanus; 9 September 1737 – 4 December 1798) was an Italian physician, physicist, biologist and philosopher, who studied animal electricity. In 1780, he discovered that the muscles of dead frogs' legs ...

(1737–1798) that

nerve A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system. A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...

s and

muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...

s were electrically excitable. The stimulation of the surface of the

cerebral cortex The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. The cerebral cortex mostly consists of the six-layered neocortex, with just 10% consisting of ...

by using brain stimulation was used to investigate the

motor cortex The motor cortex is the region of the cerebral cortex believed to be involved in the planning, control, and execution of voluntary movements. The motor cortex is an area of the frontal lobe located in the posterior precentral gyrus immediately a ...

in animals by researchers such as

Eduard Hitzig Eduard Hitzig (6 February 1838 – 20 August 1907) was a German neurologist and neuropsychiatrist of Jewish ancestryAndrew P. Wickens, ''A History of the Brain: From Stone Age Surgery to Modern Neuroscience'', Psychology Press (2014), p. 226 b ...

(1838–1907),

Gustav Fritsch Gustav Theodor Fritsch (5 March 1838 – 12 June 1927) was a German anatomist, anthropologist, traveller and physiologist from Cottbus. Fritsch studied natural science and medicine in Berlin, Breslau and Heidelberg. In 1874 he became an ass ...

(1838–1927),

David Ferrier Sir David Ferrier FRS (13 January 1843 – 19 March 1928) was a pioneering Scottish neurologist and psychologist. Ferrier conducted experiments on the brains of animals such as monkeys and in 1881 became the first scientist to be prosecuted u ...

(1842–1928) and

Friedrich Goltz Friedrich Leopold Goltz (14 August 1834 – 5 May 1902) was a German physiologist and nephew of the writer Bogumil Goltz. Born in Posen (Poznań), Grand Duchy of Posen, he studied medicine at the University of Königsberg, and following two year ...

(1834–1902). The human cortex was also stimulated electrically by

neurosurgeon Neurosurgery or neurological surgery, known in common parlance as brain surgery, is the medical specialty concerned with the surgical treatment of disorders which affect any portion of the nervous system including the brain, spinal cord and peri ...

s and

neurologist Neurology (from el, νεῦρον (neûron), "string, nerve" and the suffix -logia, "study of") is the branch of medicine dealing with the diagnosis and treatment of all categories of conditions and disease involving the brain, the spinal c ...

s such as

Robert Bartholow Roberts Bartholow or Robert Bartholow (November 28, 1831 – May 10, 1904) was an American physician and a professor at several American medical colleges. He is best known for his experiments involving a 30-year-old patient named Mary Rafferty. R ...

(1831–1904) and

Fedor Krause Fedor Krause (10 March 1857 – in Friedland in Niederschlesien; 20 September 1937 in Bad Gastein) was a German neurosurgeon who was native of Friedland (Lower Silesia). Biography He originally studied music at the Conservatoire in Berl ...

(1857–1937). In the following century, the technique was improved by the invention of the stereotactic method by British neurosurgeon pioneer

Victor Horsley Sir Victor Alexander Haden Horsley (14 April 1857 – 16 July 1916) was a British scientist and professor. He was born in Kensington, London. Educated at Cranbrook School, Kent, he studied medicine at University College London and in Berlin, Ge ...

(1857–1916), and by the development of

chronic electrode implants A chronic electrode implant is an electronic device implanted chronically (for a long period) into the brain or other electrically excitable tissue. It may record electrical impulses in the brain or may stimulate neurons with electrical impulses f ...

by Swiss neurophysiologist

Walter Rudolf Hess Walter Rudolf Hess (17 March 1881 – 12 August 1973) was a Swiss physiologist who won the Nobel Prize in Physiology or Medicine in 1949 for mapping the areas of the brain involved in the control of internal organs. He shared the prize with Eg ...

(1881–1973), José Delgado (1915–2011) and others, by using

electrode An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials de ...

s manufactured by straight insulated

wire Overhead power cabling. The conductor consists of seven strands of steel (centre, high tensile strength), surrounded by four outer layers of aluminium (high conductivity). Sample diameter 40 mm A wire is a flexible strand of metal. Wire is c ...

that could be inserted deep into the brain of freely-behaving animals, such as

cat The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of ...

s and

monkey Monkey is a common name that may refer to most mammals of the infraorder Simiiformes, also known as the simians. Traditionally, all animals in the group now known as simians are counted as monkeys except the apes, which constitutes an incomple ...

s. This approach was used by Dr.

James Olds James Olds (May 30, 1922 – August 21, 1976) was an American psychologist who co-discovered the pleasure center of the brain with Peter Milner while he was a postdoctoral fellow at McGill University in 1954. He is considered to be one of the fou ...

(1922–1976) and colleagues to discover

brain stimulation reward Brain stimulation reward (BSR) is a pleasurable phenomenon elicited via direct stimulation of specific brain regions, originally discovered by James Olds and Peter Milner. BSR can serve as a robust operant reinforcer. Targeted stimulation activat ...

and the

pleasure center The reward system (the mesocorticolimbic circuit) is a group of neural structures responsible for incentive salience (i.e., "wanting"; desire or craving for a reward and motivation), associative learning (primarily positive reinforcement and class ...

. American-Canadian neurosurgeon

Wilder Penfield Wilder Graves Penfield (January 26, 1891April 5, 1976) was an American Canadians, American-Physicians in Canada, Canadian neurosurgeon. He expanded brain surgery's methods and techniques, including mapping the functions of various regions of th ...

(1891–1976) and colleagues at the

Montreal Neurological Institute The McGill University Health Centre (MUHC; french: Centre universitaire de santé McGill) is one of two major healthcare networks in the city of Montreal, Quebec. It is affiliated with McGill University and is one of the largest medical complex in ...

used extensive electrical stimulation of the brain cortex in awake neurosurgical patients to investigate the motor and sensory

homunculus A homunculus ( , , ; "little person") is a representation of a small human being, originally depicted as small statues made out of clay. Popularized in sixteenth-century alchemy and nineteenth-century fiction, it has historically referred to the ...

(the representation of the body in the brain cortex according to the distribution of motor and sensory territories). EBS remains inextricably entwined with the work of Drs.

Robert Galbraith Heath Robert Galbraith Heath (May 9, 1915 – September 21, 1999) was an American psychiatrist. He followed the theory of biological psychiatry that organic defects were the sole source of mental illness, and that consequently mental problems were tr ...

, Delgado and Penfield. It's of interest that during cerebral localization studies, neurosurgeon Penfield could not elicit emotional reactions in humans, either by observing spontaneous epilepsy or by electrically stimulating the surface of the cerebral cortex. Neurophysiologist Delgado noted a few exceptions to this rule. In contrast, EBS, via deeply implanted electrodes in localized areas of the brain (

deep brain stimulation Deep brain stimulation (DBS) is a neurosurgical procedure involving the placement of a medical device called a neurostimulator, which sends electrical impulses, through implanted electrodes, to specific targets in the brain (the brain nucleu ...

; DBS), elicited both pleasurable and aversive responses in laboratory animals and humans as previously described. EBS could elicit the ritualistic, motor responses of sham rage in cats by stimulation of the anterior

hypothalamus The hypothalamus () is a part of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrine system via the pituitary gland. The hypothalamu ...

, as well as more complex emotional and behavioral components of "true rage" in both experimental animals by stimulation of the lateral hypothalamus, and in human subjects by stimulating various deep areas of the brain. EBS in human patients with

epilepsy Epilepsy is a group of non-communicable neurological disorders characterized by recurrent epileptic seizures. Epileptic seizures can vary from brief and nearly undetectable periods to long periods of vigorous shaking due to abnormal electrical ...

could trigger seizures on the surface of the brain and pathologic aggression and rage with stimulation of the amygdala.

Process

Two-photon excitation microscopy Two-photon excitation microscopy (TPEF or 2PEF) is a fluorescence imaging technique that allows imaging of living tissue up to about one millimeter in thickness, with 0.64 μm lateral and 3.35 μm axial spatial resolution. Unlike traditional flu ...

has shown that

microstimulation Microstimulation is a technique that stimulates a small population of neurons by passing a small electrical current through a nearby microelectrode. Applications Microstimulation is used in neuroanatomical research to identify the functional sig ...

activates neurons sparsely around the electrode even at low currents (as low as 10 μA) up to distances as far as four millimeters away. This happens without particularly selecting other neurons much nearer the electrode's tip. This is due to activation of neurons being determined by whether they do or do not have

axon An axon (from Greek ἄξων ''áxōn'', axis), or nerve fiber (or nerve fibre: see spelling differences), is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action po ...

s or

dendrite Dendrites (from Greek δένδρον ''déndron'', "tree"), also dendrons, are branched protoplasmic extensions of a nerve cell that propagate the electrochemical stimulation received from other neural cells to the cell body, or soma, of the n ...

s that pass within a radius of 15 μm near the tip of the electrode. As the current is increased the volume around the tip that activates neuron axons and dendrites increases and with this the number of neurons activated. Activation is most likely to be due to direct

depolarization In biology, depolarization or hypopolarization is a change within a cell, during which the cell undergoes a shift in electric charge distribution, resulting in less negative charge inside the cell compared to the outside. Depolarization is esse ...

rather than synaptic activation.

Effects

A comprehensive review of EBS research compiled a list of many different acute impacts of stimulation depending on the brain region targeted. Following are some examples of the effects documented: * ''Sensory'': Feelings of body tingling, swaying, movement, suffocation, burning, shock, warmth,

paresthesia Paresthesia is an abnormal sensation of the skin (tingling, pricking, chilling, burning, numbness) with no apparent physical cause. Paresthesia may be transient or chronic, and may have any of dozens of possible underlying causes. Paresthesias ar ...

, feeling of falling,

oscillopsia Oscillopsia is a visual disturbance in which objects in the visual field appear to oscillate. The severity of the effect may range from a mild blurring to rapid and periodic jumping. Oscillopsia is an incapacitating condition experienced by many p ...

dysesthesia Dysesthesia is an unpleasant, abnormal sense of touch. Its etymology comes from the Greek word "dys," meaning "bad," and "aesthesis," which means "sensation" (abnormal sensation). It often presents as painphosphenes A phosphene is the phenomenon of seeing light without light entering the eye. The word ''phosphene'' comes from the Greek words ''phos'' (light) and ''phainein'' (to show). Phosphenes that are induced by movement or sound may be associated wit ...

, hallucinations,

micropsia Micropsia is a condition affecting human visual perception in which objects are perceived to be smaller than they actually are. Micropsia can be caused by optical factors (such as wearing glasses), by distortion of images in the eye (such as optica ...

diplopia Diplopia is the simultaneous perception of two images of a single object that may be displaced horizontally or vertically in relation to each other. Also called double vision, it is a loss of visual focus under regular conditions, and is often v ...

, etc. * ''Motor'': Eye movements, locomotion, speech arrest,

automatisms Automatism refers to a set of brief unconscious behaviors. These typically last for several seconds to minutes or sometimes longer, a time during which the subject is unaware of his/her actions. This type of automatic behaviour often occurs in c ...

, laughter,

palilalia Palilalia (from the Greek πάλιν (''pálin'') meaning "again" and λαλιά (''laliá'') meaning "speech" or "to talk"), a complex tic, is a language disorder characterized by the involuntary repetition of syllables, words, or phrases. It has ...

, chewing, urge to move, crying without feeling sad, etc. * ''Autonomic'': Blushing,

mydriasis Mydriasis is the dilation of the pupil, usually having a non-physiological cause, or sometimes a physiological pupillary response. Non-physiological causes of mydriasis include disease, trauma, or the use of certain types of drugs. Normally, as ...

, change in blood pressure and breathing,

apnea Apnea, BrE: apnoea, is the temporal cessation of breathing. During apnea, there is no movement of the muscles of inhalation, and the volume of the lungs initially remains unchanged. Depending on how blocked the airways are ( patency), there ...

, nausea,

tachycardia Tachycardia, also called tachyarrhythmia, is a heart rate that exceeds the normal resting rate. In general, a resting heart rate over 100 beats per minute is accepted as tachycardia in adults. Heart rates above the resting rate may be normal (su ...

, sweating, etc. * ''Emotional'': Anxiety, mirth, feeling of unreality, fear, happiness, anger, sadness, transient acute depression,

hypomania Hypomania (literally "under mania" or "less than mania") is a mental and behavioural disorder, characterised essentially by an apparently non-contextual elevation of mood (euphoria) that contributes to persistently disinhibited behaviour. The ...

, etc. * ''Cognitive'':

Acalculia Acalculia is an acquired impairment in which people have difficulty performing simple mathematical tasks, such as adding, subtracting, multiplying and even simply stating which of two numbers is larger. Acalculia is distinguished from dyscalcul ...

paraphasia Paraphasia is a type of language output error commonly associated with aphasia, and characterized by the production of unintended syllables, words, or phrases during the effort to speak. Paraphasic errors are most common in patients with fluent for ...

anomic aphasia Anomic aphasia (also known as dysnomia, nominal aphasia, and amnesic aphasia) is a mild, fluent type of aphasia where individuals have word retrieval failures and cannot express the words they want to say (particularly nouns and verbs). By contra ...

, recalling memories, "going into a trance", "out of this world",

conduction aphasia Conduction aphasia, also called associative aphasia, is an uncommon form of difficulty in speaking (aphasia). It is caused by damage to the parietal lobe of the brain. An acquired language disorder, it is characterised by intact auditory comprehen ...

hemispatial neglect Hemispatial neglect is a neuropsychological condition in which, after damage to one hemisphere of the brain (e.g. after a stroke), a deficit in attention and awareness towards the side of space opposite brain damage (contralesional space) is obser ...

, alexia,

déjà vu ''Déjà vu'' ( , ; "already seen") is a French loanword for the phenomenon of feeling as though one has lived through the present situation before.Schnider, Armin. (2008). ''The Confabulating Mind: How the Brain Creates Reality''. Oxford Univer ...

, reliving past experiences,

agraphia Agraphia is an acquired neurological disorder causing a loss in the ability to communicate through writing, either due to some form of motor dysfunction or an inability to spell. The loss of writing ability may present with other language or neur ...

apraxia Apraxia is a motor disorder caused by damage to the brain (specifically the posterior parietal cortex or corpus callosum), which causes difficulty with motor planning to perform tasks or movements. The nature of the damage determines the disorder' ...

, etc. EBS in face-sensitive regions of the

fusiform gyrus The fusiform gyrus, also known as the ''lateral occipitotemporal gyrus'','' ''is part of the temporal lobe and occipital lobe in Brodmann area 37. The fusiform gyrus is located between the lingual gyrus and parahippocampal gyrus above, and the inf ...

caused a patient to report that the faces of the people in the room with him had "metamorphosed" and became distorted: "Your nose got saggy, went to the left. ..Only your face changed, everything else was the same."

Therapeutic applications

Examples of therapeutic EBS are: *

Cranial electrotherapy stimulation Cranial electrotherapy stimulation (CES) is a form of neurostimulation that delivers a small, pulsed, alternating current via electrodes on the head. CES is used with the intention of treating a variety of conditions such as anxiety, depression a ...

(CES) *

Deep brain stimulation Deep brain stimulation (DBS) is a neurosurgical procedure involving the placement of a medical device called a neurostimulator, which sends electrical impulses, through implanted electrodes, to specific targets in the brain (the brain nucleu ...

(DBS) *

Transcranial direct current stimulation Transcranial direct current stimulation (tDCS) is a form of neuromodulation that uses constant, low direct current delivered via electrodes on the head. It was originally developed to help patients with brain injuries or neuropsychiatric conditio ...

(tDCS) *

Electroconvulsive therapy Electroconvulsive therapy (ECT) is a psychiatry, psychiatric treatment where a generalized seizure (without muscular convulsions) is electrically induced to manage refractory mental disorders.Rudorfer, MV, Henry, ME, Sackeim, HA (2003)"Electroco ...

(ECT) *

Low Field Magnetic Stimulation Pulsed electromagnetic field therapy (PEMFT, or PEMF therapy), also known as low field magnetic stimulation (LFMS) uses electromagnetic fields in an attempt to heal non-union fractures and depression. By 2007 the FDA had cleared several such sti ...

(LFMS) *

Functional electrical stimulation Functional electrical stimulation (FES) is a technique that uses low-energy electrical pulses to artificially generate body movements in individuals who have been paralyzed due to injury to the central nervous system. More specifically, FES can ...

(FES) * Magnetic seizure therapy (MST) *

Vagus nerve stimulation Vagus nerve stimulation (VNS) is a medical treatment that involves delivering electrical impulses to the vagus nerve. It is used as an add-on treatment for certain types of intractable epilepsy and treatment-resistant depression. Medical use VN ...

(VNS) *

Deep transcranial magnetic stimulation Transcranial magnetic stimulation (TMS) is a noninvasive form of neurostimulation, brain stimulation in which a changing magnetic field is used to induce an electric current at a specific area of the brain through electromagnetic induction. An ele ...

(Deep TMS) *

Responsive nerve stimulation Responsive (formerly RFPIO, Inc.) is a privately owned developer of cloud-based software that automates and streamlines the process of responding to a request for proposal (RFP) based in Beaverton, Oregon. The company also maintains an office in ...

(RNS) Strong electric currents may cause a localized lesion in the nervous tissue, instead of a functional reversible stimulation. This property has been used for neurosurgical procedures in a variety of treatments, such as for

Parkinson's disease Parkinson's disease (PD), or simply Parkinson's, is a long-term degenerative disorder of the central nervous system that mainly affects the motor system. The symptoms usually emerge slowly, and as the disease worsens, non-motor symptoms becom ...

, focal

and

psychosurgery Psychosurgery, also called neurosurgery for mental disorder (NMD), is the neurosurgical treatment of mental disorder. Psychosurgery has always been a controversial medical field. The modern history of psychosurgery begins in the 1880s under th ...

. Sometimes the same electrode is used to probe the brain for finding defective functions, before passing the lesioning current (

electrocoagulation Electrocoagulation (EC) is a technique used for wastewater treatment, wash water treatment, industrially processed water, and medical treatment. Electrocoagulation has become a rapidly growing area of wastewater treatment due to its ability to remo ...

References

{{Reflist Brain–computer interfacing Neurophysiology Neurology procedures Electrotherapy Physical psychiatric treatments Human subject research in psychiatry