Brain stimulation therapy is one of the next major frontiers in medical science. These therapies have already shown great promise in the treatment of neurological and mental disorders from Parkinson’s disease to major clinical depression. 

Yet brain stimulation therapies are likely still in their infancy; current and ongoing research of brain networks and corresponding treatments suggests that future therapies could treat a much wider range of pathologies with greater efficacy. This article will discuss the history, current state, and future potential of brain stimulation therapy, and how it could change the lives of countless patients to come. 

History of brain stimulation therapy in treating mental health

Humans have long been curious about brain stimulation and how it might be used to treat illness, but the first true brain stimulation therapy did not take place until the twentieth century. 

What were the first forms of brain stimulation therapy?

Brain stimulation therapy has a surprisingly long history. The first mention of intentional brain stimulation for medical purposes appears in an ancient Roman text from 46 AD; the text recommends applying electric ray fish to the head in order to relieve headache. 

Although early scientists explored brain stimulation in cadavers and animals throughout the 1700-1800s, the first modern use of brain stimulation therapy occurred in 1938 in the form of electroshock therapy administered by Italian neurologist Ugo Cerletti to patients suffering from severe psychosis. 

As early as 1950, scientists successfully implanted temporary electrodes into the cranial regions of human subjects in order to control pain. This opened the door to further research and development of new brain stimulation techniques, including transcranial magnetic stimulation, cortical brain stimulation, and deep brain stimulation.

How has brain stimulation therapy developed over the years?

Initial brain stimulation therapies in the 1930s were largely unable to localize target areas within the brain. X-ray pneumoencephalography, a procedure in which cerebrospinal fluid was replaced by air, oxygen, or helium in order to facilitate X-ray imaging of the brain, allowed physicians to localize and target brain lesions with much greater accuracy, albeit at the cost of severe pain and side effects for the patient. Physicians were able to develop a body of knowledge regarding the effects of stimulating various areas of the brain. 

Throughout the 1950s, brain stimulation was most frequently used to treat Parkinson’s disease. When the new pharmaceutical levodopa appeared effective for treating Parkinson’s disease in the 1960s, physicians largely halted their use of brain stimulation, considering it too risky and invasive an alternative to levodopa. In addition, public perception of neurotherapies and treatments had soured as word spread of controversial treatments like lobotomies and electroshock therapy.

However, brain stimulation therapy experienced a resurgence in the 1980s, when it became clear levodopa was not always effective for long-term use in patients with Parkinson’s disease. By the 1990s, deep brain stimulation had become a viable alternative for treating Parkinson’s disease. Initially, brain stimulation implants included a radiofrequency receiver coil implant that was attached to electrodes, with an external battery device. Later designs developed integrated batteries. 

What is brain stimulation therapy like today?

Today’s brain stimulation therapies, both established and experimental, include the following:

  • Electroconvulsive therapy (ECT): ECT has the most research behind it and has been used the longest. This therapy involves placing electrodes at precise locations on the patient’s head and administering an electric current to the patient’s brain. ECT is typically used to treat severe mental disorders, such as depression, bipolar disorder, or schizophrenia, that have not responded to other forms of treatment. 
  • Repetitive transcranial magnetic stimulation (rTMS): rTMS uses an electromagnetic coil to deliver magnetic stimulation to specific sites of the brain. This therapy is used to treat mental disorders like psychosis, anxiety, and especially severe depression. There is much still to discover about how best to use rTMS, especially regarding its effectiveness when combined with pharmaceuticals or psychotherapy. 
  • Magnetic seizure therapy (MST): MST is still an experimental procedure, but early studies have shown promising results regarding its effectiveness to treat major depression and bipolar disorder. MST delivers strong magnetic pulses to the brain in order to trigger a brief seizure. This therapy is intended as an alternative to ECT that may induce fewer side effects. 
  • Deep brain stimulation (DBS): DBS was first developed to treat Parkinson’s Disease, although scientists are currently studying its efficacy in treating depression and obsessive-compulsive disorder (OCD). DBS requires a minimally invasive brain surgery procedure that involves implanting electrodes in the brain, attaching those electrodes to wires, and attaching the wires to generators surgically implanted in the patient’s chest. The electrodes then deliver continuous electrical stimulation to the brain. 

Brain stimulation therapy for mental and neurological health

Brain stimulation therapy holds great promise for treating a range of illnesses that hitherto have not had highly effective medical solutions available. These therapies have already shown efficacy in treating diseases like Parkinson’s disease, and current research indicates potential future uses for a variety of pathologies. 

How can brain stimulation aid memory and brain health?

Scientists do not yet fully understand why brain stimulation can have a positive effect on patients suffering from various psychological and neurological disorders. Current and future research will be focused on learning more about why these therapies work. 

However, researchers have uncovered some data about why brain stimulation therapies are effective. It appears that brain stimulation therapy activates neurons in targeted regions of the brain that are underactive in patients suffering from disorders. 

Research is underway to find out the effect brain stimulation can have on memory and learning. Many studies have suggested brain stimulation is effective when paired with other types of training and mnemonic devices. Some studies have indicated that brain stimulation could be used alongside mental exercises to improve mild Alzheimer’s disease. 

DBS has shown significant potential as a treatment for Parkinson’s disease. In 2002, DBS was approved to treat advanced Parkinson’s. As of 2016, it was approved for earlier stages of the disease. Though most patients continue to use medication in conjunction with DBS, this form of brain stimulation therapy has been shown to relieve symptoms in a significant percentage of patients. 

What is the success rate of brain stimulation therapy for mental and neurological health?

The success rate of brain stimulation therapy for treating mental health is not yet fully known. However, a small study published in the American Journal of Psychiatry in April 2020 showed that a new form of rTMS involving precisely targeted higher stimulation doses at greater frequency rapidly resolved treatment-resistant depression in nineteen of twenty-one participants—an 86.4 percent success rate. 

In terms of DBS’s effectiveness to treat Parkinson’s disease, a long-term study published in 2019 associated DBS with a ten-year survival rate of 51 percent. The study also showed that almost all the patients (92.5 percent) were happy with DBS therapy, and 75 percent felt it helped control their symptoms. 

What mental and neurological health conditions can be targeted with brain stimulation therapy?

Brain stimulation has so far been approved to treat conditions including the following:

  • Parkinson’s disease
  • Mood disorders (depression, anxiety, bipolar disorder)
  • Epilepsy
  • Essential tremor
  • Dystonia

Brain stimulation is still being studied as a possible treatment for conditions such as the following:

  • Addiction
  • Dementia
  • Multiple sclerosis
  • Tourette syndrome 
  • Traumatic brain injury
  • Huntington’s disease
  • Stroke recovery
  • Chronic pain
  • Eating disorders

Brain stimulation therapies for the clinician

Since brain stimulation affects the brain—the center of human consciousness, personality, and cognition—clinicians must follow medical guidelines and adhere to strict ethical standards when considering brain stimulation therapy for a patient. 

What factors must be present for deep brain stimulation to work?

The Pacific Neuroscience Institute has helpful guidelines regarding factors that should be present as clinicians attempt DBS:

  1. Confirming that the diagnosis is accurate. A preoperative evaluation is necessary to ensure that the condition has been correctly diagnosed, and is of the variety that can be treated with DBS. 
  2. Targeting the correct region of the brain for the greatest benefit to the patient. 
  3. Precisely placing electrodes within the patient’s brain according to historical brain atlases, in addition to the specific anatomy of the patient. 
  4. Ensuring proper postoperative care and device programming. Each patient should receive personalized care targeted to his or her unique case in terms of brain imaging, symptom management, and simultaneous treatments such as physical therapy or medication. 

What are some of the side effects of brain stimulation therapies?

Brain stimulation therapies hold risks to varying degrees. DBS has the highest potential for complications and side effects, since it’s an invasive brain surgery procedure. Risks of DBS may include the following:

  • Brain hemorrhage 
  • Breathing difficulties
  • Heart problems
  • Seizure
  • Infection
  • Stroke

Side effects of noninvasive brain stimulation therapies, such as ECT, VNS, rTMS, and MST, may include the following:

  • Confusion
  • Memory loss
  • Physical discomfort such as nausea or headache
  • Heart problems due to increased blood pressure during the procedure

What should clinicians be aware of before performing brain stimulation therapy?

Clinicians should fully investigate the appropriateness of brain stimulation therapy for each unique patient. According to the American Association of Neurological Surgeons, when considering brain stimulation therapy—especially DBS—for a patient, clinicians must observe the following criteria in the patient:

  • The patient’s symptoms are substantially reducing quality of life.
  • The patient’s symptoms are uncontrolled despite receiving the suitable dose of medications.
  • The patient cannot tolerate the side effects of current medications.

Immediately preceding a DBS procedure, patients must undergo blood and urine testing to identify any abnormalities, in addition to brain imaging in order to locate the target area of the brain. 

Advanced research on brain stimulation therapy

As this article has discussed, brain stimulation therapy is very much still in development, with many exciting possibilities on the horizon. Researchers will have to surmount certain uncertainties and controversies as they develop the next generation of these neurotechnologies.

What is currently in development for brain stimulation therapy?

Next-generation closed-loop neurotechnologies are currently in development. Based on past technology trajectories, these neurotechnologies are likely to be ready for use by 2030-2040. Closed-loop neurotechnologies refer to technologies that have the ability to sense the effects of brain stimulation and adjust based on feedback; these technologies will have the ability to operate mostly autonomously alongside the patient’s own neural and motor functions.

Scientists developing future closed-loop neuromodulation technologies are seeking to create or strengthen the following features within these technologies: 

  • Feedback-based dynamic stimulation to better achieve desired outcomes
  • Improved safety at all points 
  • Design that can integrate seamlessly with human physiology
  • More location-specific and precise neural targets
  • Greater customization for each patient 
  • Greater device autonomy

What are future possibilities for brain stimulation therapies?

There is promising evidence that future brain stimulation therapies will be able to treat a much wider range of neurological, psychiatric, behavioral, and cognitive pathologies. Researchers are currently studying how to treat diseases and disorders such as chronic pain, epilepsy, mood disorders, eating disorders, cognitive decline such as dementia or Alzheimer’s disease, and addiction. 

What are current controversies or uncertainties for brain stimulation therapy?

Brain stimulation therapies are currently inhibited by several factors. One such factor is the variability of side effects, as well as the difficulty of reproducing results from patient to patient. Another factor is the sheer technological complexity of brain stimulation systems. 

Brain stimulation therapies have attracted controversy from people concerned that these technologies could be used to manipulate or abuse—for example, as a tool to treat undesirable or “immoral” behavior, or to provide inequitable cognitive enhancement to certain members of the population. 

However, these therapies are relatively safe, mostly reversible, and guided by strict medical ethics standards (e.g., they are only used in otherwise treatment-resistant patients who provide informed consent). Therefore, these concerns, while important to consider, are largely mitigated by the circumstances surrounding the technologies as they are today. 

Achieving next-generation neurotechnologies

Brain stimulation therapies have a long way to go, but they have already helped thousands of patients and hold great potential for helping countless more in future years. While more research and development must occur within the field of brain stimulation therapy, the possibilities are exciting. 

IEEE is passionate about advancing technology for humanity. To learn more about next-generation closed-loop neurotechnologies and what must be done to achieve them, download IEEE’s “Future Neural Therapeutics” white paper.

Read “Future of Neural Therapeutics: Technology Roadmap White Paper


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