TMS & Other Therapies

Study Uses TMS to Investigate Empathy for Pain

August 28, 2019

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Transcranial magnetic stimulation (TMS) is a psychiatric treatment that uses magnetic pulses to trigger electrical reactions in the brain, which can help improve symptoms of mental health conditions such as depression. 

However, TMS is also used as a tool in scientific studies concerning the brain and other neurological functions. Recently, researchers used TMS to record psychological responses to perceiving pain in others. 

Continue reading to find out more regarding:

The Study: Empathy and the Sensorimotor System

Background

Our brains use personal experiences relating to pain (both physical and emotional) to create what is known as a “pain matrix.” It is through this compilation of memories and experience-derived learning that we are able to feel empathy for someone else’s pain. Furthermore, empathy causes a chemical change in our brains that imitates what occurs when we ourselves are in pain. 

Visual representation of empathy and pain in the brain
Even though pain is a subjective experience, memories of our own pain allows us to feel empathy for other people. Image courtesy of Adonis Sfera, M.D., on SlideShare

Because both pain and empathy are neural phenomena, the brain’s pain systems and the action systems are linked, enabling us to have the appropriate social reaction to witnessing another person in pain. 

Researchers from this study, which is titled “Transcranial magnetic stimulation highlights the sensorimotor side of empathy for pain” and was published in the journal Nature Neuroscience, “explored whether pain and action systems are linked also at a social level by looking for possible motor correlates of watching and empathizing with others' pain.” 

Methods 

Participants in the study were shown needles penetrating the hands or feet of dummies or inanimate objects. The researchers used single-pulse TMS to analyze the subjects’ internal physical responses while they observed the dummy or the object being pricked by the needle. 

For comparison, the researchers also showed the participants a Q-tip lightly touching the surface of the dummy’s hand or applying pressure to it. 

The participants’ responses were recorded via the TMS machine, which processed motor-evoked potentials (MEPs) from two different hand muscles. Participants provided their own subjective, conscious interpretations of what they were shown by filling out questionnaires as well as visual analogue scales rating pain intensity and pain unpleasantness. 

Findings

The researchers found reduced MEPs only in the muscle that the subjects observed saw being pricked. “This inhibition correlated with the observer's subjective rating of the sensory qualities of the pain attributed to the model and with sensory, but not emotional, state or trait empathy measures,” they reason. “The empathic inference about the sensory qualities of others' pain and their automatic embodiment in the observer's motor system may be crucial for the social learning of reactions to pain.” 

TMS and Its Versatility 

A Groundbreaking Psychiatric Treatment

As mentioned earlier, the primary use for TMS is as a therapy to treat mental health conditions—most commonly depression. In 2008, the FDA approved TMS as a treatment option for major depressive disorder. More recently, in 2018, it was approved to treat obsessive compulsive disorder (OCD). 

Animated representation of how TMS works to treat depression
TMS targets the areas of the brain that are most affected by depression. Stimulating these regions can improve mood and reduce symptoms of depression, such as fatigue, restlessness, and more. Image courtesy of Mass General Hospital

During TMS treatment, an electromagnetic coil is placed against the patient’s head, allowing the magnetic pulses to penetrate the skull and interact with the brain. This process is relatively painless, though it may take some time for the patient to adjust to the noise made by the machine, which is similar to that heard during an MRI. 

Technician applies TMS to a patient
A typical session of TMS lasts around forty minutes, though this may vary from patient to patient. Image courtesy of In Public Safety

TMS is non-invasive and does not affect cognitive function, so after a session, the patient can resume daily activity, including driving. In order for TMS to be effective, it must be administered daily for about six weeks. Other than a light headache or irritation around the treatment site, there are no side effects to receiving TMS. 

Though it has only been FDA-approved to treat depression and OCD, TMS is being tested as a treatment option for a wide array of conditions, including Parkinson’s disease, attention-deficit hyperactivity disorder, Asperger syndrome, panic disorder, post-traumatic stress disorder, and more. 

An Innovative Research Tool 

According to the Journal of Visualized Experiments, “By selectively interfering with regionally-specific cortical processing, TMS can be used to draw causal links between brain regions and specific behaviors.” 

Additionally, researchers can use TMS “to investigate the time course of neural information processing by using very short bursts of stimulation and varying the onset of stimulation. Typically this involves either a single or double pulse TMS delivered to a region at different points of time within a trial.” 

TMS is used for research in almost every area of cognitive neuroscience. This includes attention, memory, visual processing, action planning, decision making, and language processing. 

Interested in TMS? Ask Your Doctor About It Today. 

Though it is not a first-line treatment, TMS is continually growing in popularity and has been a part of mainstream psychiatry for a number of years. Many patients with treatment-resistant depression have had success with TMS, and because of the non-drug nature of the treatment, most patients can continue taking their medications while undergoing TMS. 

If you have major depressive disorder that has persisted despite treatment by antidepressants and psychotherapy, ask your doctor about TMS. You might be one of the many people who can benefit from it. 

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