How electroconvulsive therapy heals the brain − recent insights into ECT, a stigmatized yet highly effective treatment for depression

When most individuals hear about electroconvulsive therapy, or ECT, it typically conjures terrifying images of cruel, outdated and pseudo-medical procedures. Formerly often known as electroshock therapy, this perception of ECT as dangerous and ineffective has been reinforced in popular culture for many years – think the 1962 novel-turned-Oscar-winning film “One Flew Over the Cuckoo’s Nest,” where an unruly patient is subjected to ECT as punishment by a tyrannical nurse.

Despite this stigma, ECT is a highly effective treatment for depression – as much as 80% of patients experience at the least a 50% reduction in symptom severity. For considered one of the most disabling illnesses around the globe, I believe it’s surprising that ECT is rarely used to treat depression.

Contributing to the stigma around ECT, psychiatrists still don’t know exactly the way it heals a depressed person’s brain. ECT involves using highly controlled doses of electricity to induce a transient seizure under anesthesia. Often, the perfect description you’ll hear from a physician on why that transient seizure can alleviate depression symptoms is that ECT “resets” the brain – a solution that might be fuzzy and unsettling to some.

As a data-obsessed neuroscientistI used to be also dissatisfied with this explanation. In our newly published researchmy colleagues and I in the lab of Bradley Voytek at UC San Diego discovered that ECT might work by resetting the brain’s electrical background noise.

Listening to brain waves

To study how ECT treats depression, my team and I used a tool called an electroencephalogram, or EEG. It measures the brain’s electrical activity – or brain waves – via electrodes placed on the scalp. You can consider brain waves as music played by an orchestra. Orchestral music is the sum of many instruments together, very like EEG readings are the sum of the electrical activity of hundreds of thousands of brain cells.

Two sorts of electrical activity make up brain waves. The first, oscillations, are just like the highly synchronized, melodic music you would possibly hear in a symphony. The second, aperiodic activity, is more just like the asynchronous noise you hear as musicians tune their instruments. These two sorts of activities coexist within the brain, together creating the electrical waves an EEG records.

Importantly, tuning noises and symphonic music shouldn’t be mistaken for each other. They clearly come from different processes and serve different purposes. The brain is analogous in this manner – aperiodic activity and oscillations are different since the biology driving them is distinct.

However, the methods neuroscientists have traditionally used to investigate these signals are unable to distinguish between the oscillations (symphony) and the aperiodic activity (tuning). Both are critical for the orchestra, but to this point neuroscientists have mostly ignored – or entirely missed – aperiodic signals because they were regarded as just the brain’s background noise.

In our recent research, my team and I show that ignoring aperiodic brain activity likely explains the confusion behind about how ECT treats depression. It seems we’ve been missing this signal all along.

Connecting aperiodic activity and ECT

Since the Nineteen Forties, ECT has been related to increases in slow oscillations within the brain waves of patients. However, those slow oscillations have never been linked to how ECT works. The degree to which slow oscillations appear is just not consistently related to how much symptoms improve following ECT. Nor have ideas about how the brain produces slow oscillations connected those processes to the pathology underlying depression.

Because these two sorts of brain waves are difficult to separate in measurementsI wondered if these slow oscillations were in reality incorrectly measured aperiodic activity. Returning to our orchestra analogy, I believed that scientists had misidentified the tuning sounds as symphony music.

To investigate this, my team and I gathered three EEG datasets: one from nine patients with depression undergoing ECT in San Diego, one other from 22 patients in Toronto receiving ECT and a 3rd from 22 patients in Toronto participating in a clinical trial of magnetic seizure therapy, or MSTa more moderen alternative to ECT that starts a seizure with magnets as an alternative of electricity.

We found that aperiodic activity increases by greater than 40% on average following ECT. In patients who received MST treatment, aperiodic activity increases more modestly, by about 16%. After accounting for changes in aperiodic activity, we found that slow oscillations don’t change much in any respect. In fact, slow oscillations weren’t even detected in some patients, and aperiodic activity dominated their EEG recordings as an alternative.

How ECT treats depression

But what does aperiodic activity must do with depression?

An extended-standing theory of depression states that severely depressed patients have too few of a form of brain cell called inhibitory cells. These cells can turn other brain cells on and off, and maintaining the balance of those on and off states is critical for healthy brain function. This balance is especially relevant for depression since the brain’s ability to show cells off plays a crucial role in the way it responds to emphasizea function that, when not working properly, makes people particularly vulnerable to depression.

Using a mathematical model of cell type-based electrical activity, I linked increases in aperiodic activity, like those seen within the ECT patients, to an enormous change within the activity of those inhibitory cells. This change in aperiodic activity could also be restoring the crucial on and off balance within the brain to a healthy level.

Even though scientists have been recording EEGs from ECT patients for many years, that is the primary time that brain waves have been connected to this particular brain malfunction.

Altogether, though our sample size is comparatively small, our findings indicate that ECT and MST likely treat depression by resetting aperiodic activity and restoring the function of inhibitory brain cells. Further study might help destigmatize ECT and highlight recent directions for the research and development of depression treatments. Listening to the nonmusical background noise of the brain could help solve other mysteries, like how the brain changes in aging and in illnesses like schizophrenia and epilepsy.