Ever Lose Your Train of Thought?

Ever Lose Your Train of Thought?
Franklin Yeep/Flickr

Ever lose your train of thought? It’s frustrating and annoying, but it’s happened to everyone at least once.

But more than that, researchers have now linked that obnoxious tendency to an actual, scientific explanation.

On a neurological level, researchers have surveyed the brain at the moment a human being is startled (and therefore loses their train of thought), and found a surprising link between the lost-thought and a very well known symptom found in those with Parkinson’s disease.

Losing your train of thought can happen as the result of a variety of stimuli, such as being interrupted or being startled by a loud noise or other, unexpected event.


According to Adam Aron, a neuroscientist at the University of California, San Diego (also the researcher that led this study), “An unexpected event appears to clear out what you were thinking.”

The experiment ultimately shows the brain sending out an order to physically stop, thus interrupting the train of thought.

Aron said the following:

“We know what the electrical signals look like when somebody has to stop a movement. The radically new idea is that just as the brain’s stopping mechanism is involved in stopping what we’re doing with out bodies it might also be responsible for interrupting and flushing out our thoughts. We are providing a neural mechanism by which that happens. The same stopping system that gives you that kind of jolt when you are getting out of the elevator, and someone else is in your way and you have to stop, that same stopping system is stopping your train of thought.”

This stopping system in the brain is known as the “subthalamic nucleus.”

The subthalamic nucleus also happens to be the main focus of this study. The experiment was conducted with volunteers that put on an electrode hat and completed memory tasks on computers.

The first test determined whether a surprise could make the volunteers lose concentration on their task. To do so, the computer would show them a string of consonants, which they were then told to compare to another string and determine if they were identical. This requires mundane concentration.

To throw the volunteers off, a tone was used before the test part of the experiment. However, sometimes the researchers would mix up this tone by replacing it with the sounds of birds singing.

And this distractor worked. The 21 volunteers that participated in the study either slowed in their test taking or made errors in their comparisons.

Then, 22 new volunteers did the same test with the electrode hat on while seven others (with Parkinson’s disease) did a similar test, though the electrodes were implanted surgically.

These electrodes read the brain activity and gave a very precise reading in those with Parkinson’s while the electrodes in the caps gave more of a rough idea of brain activity.

The study found that volunteers were more likely to make mistakes the more the subthalamic nucleus was engaged by the “startling” sounds.

According to Jan Wessel, a cognitive neurologist at the University of Iowa that worked on the study, “We’ve shown that unexpected, or surprising, events recruit the same brain system we use to actively stop our actions, which, in turn, appears to influence the degree to which such surprising events affect out ongoing trains of thought.”

This is ironically something Parkinson’s patients are all too familiar with. The subthalamic nucleus is at work in Parkinson’s as well, and is responsible for the “freezing” qualities of the disease. For instance, when patients can’t focus easily or can’t initiate motion, this is their brain’s subthalamic nucleous, quite simply, directing the body to stop.

The electrodes mentioned above are referred to as “deep brain stimulation,” which is meant to treat these symptoms.

Because this same action is happening in “healthy” brains, researchers are led to believe that this system is a universal one, perhaps further explaining the complexities of such neurological diseases.

Of course, scientists don’t stop there either. This knowledge could help to treat depression or PTSD in the future.

According to Wessel, “It might also be potentially interesting to see if this system could be engaged deliberately — and actively used to interrupt intrusive thoughts or unwanted memories.”

Of course, these ideas are far in the future, and for the most part, just wishful thinking.

According to Aron, “We don’t want to stretch it too far to make big claims about treating anything. This is highly speculative, but it could be fruitful to explore if the subthalamic nucleus is more readily triggered in ADHD.”

This research may just be scratching the surface of its potential, but if this study is any indication, the future might just hold some of the most valuable neurological information yet.

BY Victoria Robertson