Electrical stimulation of the brain: no stress!

Electrical stimulation of the brain is now a promising way to study post-traumatic stress disorder. But rest assured, it has nothing to do with what we can imagine, explains Philippe Vignaud.

An event with traumatic potential is an event that exposes people to death or serious physical injury. Unfortunately, the events of recent years (Bataclan in Paris 2015, July 14th in Nice 2016, etc.) have this concept as well as a psychiatric illness that can arise in this context, namely the Post-traumatic stress disorder (PTSD). It consists of repeated memories (flash, nightmares), hypervigilance, and painful emotional activation when the person is confronted with elements that remind them of the event. PTSD occurs in the months following the event; It is partially scientifically known and several therapeutic tools are available. Among others, the psychotherapy technique Eye Movement Desensitization Reprocessing (EMDR) is a validated tool for treating this condition.

However, we face several problems. First, less is known about the neurobiological and physiological changes that are present in the early phase after a potentially traumatic event. Second, the therapeutic arsenal for acute stress disorder (ASD), the condition that encompasses the symptoms present at this early stage, is both less codified and less extensive. More specifically, psychotherapy, including the EMDR technique, is certainly the most effective tool to treat psychotraumatic symptoms, but it is not always available in the early stages and some patients are not very sensitive to it for various reasons. There is a need to better understand this condition and strengthen our capacity to act in the early phase after the potentially traumatic event.

For these reasons, the transcranial electrical stimulation could be an interesting path and is at the heart of my thesis. Your eyes may widen in amazement as you read this sentence… Electrostimulation?? Like in the movie One Flew Over the Cuckoo’s Nest where we see Jack Nicholson being electrocuted in an unorthodox way?? No, Don `t worry! Thankfully, that kind of scene is long gone. However, the idea of ​​stimulating the brain with electrical current continues to make its way into modern psychiatry and neuroscience. We’ll come back to that later.

A combat body

In general, when faced with a stressor, we can count on the human body, a true warrior, ready to face the threat. From the brain that takes control of operations, to the various organs that execute, to hormones that play the role of the transmission belt, we have many well-oiled mechanisms to defend ourselves throughout evolution. In my thesis project, I am particularly interested in cortisol.

sometimes nicknames fight hormone, it helps the body mobilize energy and focus that resource in response to a stressor. Its production is under the control of other hormones produced in the brain by structures that have more or less direct connections with the hormone frontal cortex. This region, located behind the forehead, plays an important role in expressing and regulating our emotions. If everything goes well, the stressor will be analyzed at the level of the brain and more specifically in the frontal cortex; At the end of the chain, cortisol is released to respond to this stressor. Once the latter is neutralized, the production of cortisol decreases and the body returns to rest. In addition, stress management mechanisms have an added quality that is the reactivity : They trigger at just the right time, just enough, just the time needed.

Did I say “general”? And yes, the story isn’t as pretty when the stressor is extreme as a potentially traumatic event. The beautiful mechanics described above go wrong. As ? In my thesis, I focus on the hypothesis that this reactivity would be altered to a stressor, specifically cortisol production.

Electrical stimulation of the brain

I’m going to talk a little more about something called “transcranial electrical stimulation.” An electric current is circulated between 2 electrodes that are placed on the patient’s skull. There is no epileptic seizure or anesthesia, people receiving such stimulation generally feel a slight warming sensation under the site of the electrodes and a non-gravity headache. The tolerability is therefore very good. This technique has been used in humans for about twenty years and has two main categories of use. On the one hand, it serves Treatment of symptoms of neurological and psychiatric diseases ; On the other hand, it helps to stimulate the brain with electrical current better understand how it works, whether in healthy subjects or in sick subjects. The parameters that can be set in many ways, such as the position of the electrodes on the brain or the type of electrical current delivered, offer numerous possibilities for scientific investigations.

Electrical stimulation of the brain (or transcranial) – experiment performed at CRNL

Exploring the stress response in a stressed person

For several years, researchers have wondered whether transcranial stimulation can influence the response to a stressor. How does it work? Very easy ! The participant is subjected to a standardized stress test that can be performed in the laboratory: soaking the hand in (very) cold water for several minutes; Do the math in your head as quickly as you can without making mistakes, otherwise you’ll have to start over; simulate an interview before a jury… During this time, the participant receives transcranial stimulation at the frontal cortex. This is a good thing, since not only does the frontal cortex likely play a role in physiological state in response to stress, including by influencing cortisol secretion, but it is also easy to target this area with the electrodes of transcranial stimulation. In healthy subjects, this stimulation appears to influence the response to a stressor, which the researchers specifically observed by monitoring cortisol release over the course of the stress test.

But then… What about the subject who has an acute stress disorder?, namely who is on high alert and whose brain could be considered permanently “stressed”? How does it react when subjected to a laboratory stress test? And could transcranial stimulation of the frontal cortex modulate cortisol secretion under these conditions? These questions are the focus of my diploma thesis!

Medicine asks questions, science constructs the answer

And then… what is it used for? Answering all of these questions will improve our knowledge of the pathophysiology of acute stress disorder. And this knowledge drives the development of new therapies. If there is no shortage of examples of “accidental” therapeutic discoveries in medicine, the most common approach remains to gradually discover the physiopathology of a disease through successive question-and-answer games until sufficiently elaborate hypotheses are formed to propose a new treatment .

Exactly…couldn’t transcranial stimulation be one of those future treatments being offered to people with acute stress disorder? I’m just at the beginning of my diploma thesis and it’s premature to answer the question with yes or no anyway. But in a few years we will probably be able to answer that and I will be very happy if my diploma thesis project becomes a part of this puzzle.

This article was written for Sciences pour tous by Philippe Vignaud, PhD student in the Psychiatric Disorders, Neuroscience and Clinical Research team (PsyR²) at the Lyon Neuroscience Research Center.

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