Everyone has happened to us on occasion. We were going to say something, but, inexplicably, we forget. For example, we are about to speak, and the sound of the phone makes you lose track of what we were saying. Psychologists call this train of thought derailed. This curious name comes from ideas, over a speech, are connected to each other, like the cars of a train and a distraction can cause us to lose the thread.
A study published in Nature Communications explains why this happens to us. And apparently responsible for the derailment of our ideas is the braking system of the brain, it makes us become paralyzed when something unexpected in everyday life that startles us, for example, the sound of the horn a car when we walk down the street.
In this case our brain reacts immediately stopping or slowing what we were doing. In the technical language we speak of a slowing engine after unexpected events. This decrease in the rate of ongoing behavior after unexpected events could help buy time for the cognitive system can assess whether an ongoing action remains appropriate when circumstances change. The slowdown of the movement after unexpected events is widespread. It comes after unexpected perceptions, errors, unexpected events or errors of prediction of a different action after an expected (errors in predicting reward) result.
The study focuses on a part of the braking system of the brain: the subthalamic nucleus (STN)
The study focuses on a part of the braking system of the brain: the subthalamic nucleus (STN) – Nathalie Belanger
A study conducted by the laboratory of neuroscientist Adam Aron, of the University of California, San Diego, collaborators at the University of Oxford in the UK, suggests that the same system of the brain involved in disrupting the movement of our body is also interrupts the thought and makes us lose the thread.
The study focuses in particular on a part of the braking system of the brain: the subthalamic nucleus (STN). It is a small group of neurons densely packed located in the midbrain, which is part of the basal ganglia, which in turn are responsible that we can carry out movements with adequate precision.
Previously Aron and his colleagues had shown that the subthalamic nucleus is activated when it is necessary to stop the action we are doing. Specifically, it may be important, Aron explains, for a “hard stop” which causes a jolt of the entire body. It is what happens when, for example, are about to leave an elevator and suddenly see that there is someone on the other side of the doors.
Similarly, “an unexpected event seems to erase what we were thinking,” Aron says. “The radically new idea is that as the stop mechanism of the brain is involved in stopping what we are doing with our body, could also be responsible for the disruption and deleting of our thoughts.”
If further research confirms the connection suggested by the current study, among the subthalamic nucleus and forgetting what we were about to say after an unexpected event, researchers believe that it could be an adaptive function of the brain. This mechanism to stop the action and thought, might have evolved long ago as a way to “reset” our cognition and allow them to focus on something new. One must go back to the time when our ancestors were still living in Africa. “You are walking one morning in the African bush, to go to collect firewood. He is dreaming of the food that will prepare, when suddenly you hear a rustle in the grass. It is for dry and all thoughts of dinner fade to focus on finding out what could have caused that noise.
In this case, forget what we thought were a second ago, to focus our mind on discovering if a lion or other dangerous animal that has made noise, is a vital issue. And stop all thought that distracts us is too. Those who follow engrossed in thought, despite signs of a potential danger, surely were less likely to pass on their genes to the next generation. While those in which the brain simultaneously slowed their movements and thoughts, could live to tell about it (her grandchildren). Hence this simultaneous braking system has been preserved to this day.
Electroencephalograms for the study of 20 healthy subjects and signals implants electrodes located in the subthalamic nucleus of seven people with Parkinson’s disease were analyzed. This disease can cause muscle tremors and slowed movement. Parkinson’s patients may also present as the “opposite of distracted” with a current of thought so stable that it may seem difficult to interrupt. The same system of the brain that is involved in motor activity abnormalities in these patients, the subthalamic nucleus, could also be keeping them focused on their thoughts. So the subthalamic nucleus is the main objective of therapeutic deep brain stimulation in Parkinson’s disease, to correct the above symptoms.
Remember these letters
In each trial, volunteers were asked to keep in mind a string of letters, which then had to remember in a test. Most of the time, while keeping in mind the letters (in his memory), and before the memory test, they heard a sound of a single frequency. But sometimes, this sound was replaced by the chirping of birds, which is not something like a shrill sound alarming, but it is unexpected and surprising when it is a mobile phone that suddenly starts chirping. The brain activity of volunteers was recorded, as well as its accuracy remember the lyrics.
The results show that unexpected events show the same “brand” in the brain activity that a sudden stop of the movement. And in both cases involved the subthalamic nucleus. And the more active is this structure, or the more answers this part of the brain to the unexpected (the chirping of birds in the mobile) sound more affected working memory participants (critical to remember something for a short period time, as in the case of the letters of the experiment) and worse could remember the lyrics trying to keep in mind.
“We have shown that unexpected or surprising events recruit the same delcerebro system we use to actively stop our actions, which, in turn, appears to influence the extent to which affect this kind of surprising to our train of thought current events” the researchers explain.
The role of the subthalamic nucleus to stop the body and disrupting working memory matches the place where this core is located within the brain circuits. However, more research is needed to determine whether there is a causal relationship between the observed activity in the subthalamic nucleus and loss of working memory, they warn.
A possible future line of research is to see whether the subthalamic nucleus and associated circuits play a role in conditions characterized by distractibility, hyperactivity disorder and attention deficit. “This is highly speculative,” notes Aron, “but it could be fruitful to explore whether the subthalamic nucleus more easily activated in ADHD.”
It could also be potentially interesting to see if this system could be deliberately and actively activated to interrupt unwanted intrusive thoughts or explain memories. Obsessive compulsive disorder (OCD) is characterized by the appearance of such intrusive thoughts difficult to contain. And also, as in Parkinson’s, in very severe, drug-resistant cases, electrodes in the subthalamic nucleus placed to interrupt these obsessive thoughts and repetition of rituals intended to stop them.
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