According to a recent study, there are a handful of words our brain will regurgitate by default. Apparently, these words can also help ascertain the health of our minds.
In a recent study of epilepsy patients and healthy volunteers, researchers from the National Institutes of Health found that our brains tend to draw on more common words, like “pig,” “tank,” and “door,” much more often than others, including “cat,” “street,” and “stair.”
Using brain wave recordings, a combination of memory tests, and surveys of billions of words published in books, news articles and internet encyclopedia pages, the researchers found not only how our brains may recall certain words but also memories of past experiences.
“We found that some words are much more memorable than others. Our results support the idea that our memories are wired into neural networks and that our brains search for these memories, just the way search engines track down information on the internet,” said Weizhen Xie, Ph.D., a cognitive psychologist and post-doctoral fellow at the NIH’s National Institute of Neurological Disorders and Stroke (NINDS).
Dr. Xie led the study published in Nature Human Behaviour. “We hope that these results can be used as a roadmap to evaluate the health of a person’s memory and brain.”
Xie and his colleagues re-analysed the results of memory tests taken by 30 epilepsy patients who were involved in a clinical trial led by Kareem Zaghloul, M.D., Ph.D., a neurosurgeon and senior investigator at NINDS. Dr. Zaghoul’s team is concerned with patients whose seizures cannot be controlled by drugs, otherwise known as intractable epilepsy. During the observation period, patients spend several days at the NIH’s Clinical Centre with surgically implanted electrodes designed to detect changes in brain activity.
“Our goal is to find and eliminate the source of these harmful and debilitating seizures,” said Dr. Zaghloul. “The monitoring period also provides a rare opportunity to record the neural activity that controls other parts of our lives. With the help of these patient volunteers, we have been able to uncover some of the blueprints behind our memories.”
The memory tests were originally designed with episodic memories in mind—in other words, the who, what where and how details we associate with past experiences. Alzheimer’s diseases and other forms of dementia destroy the brain’s capacity to generate these precious memories.
Patients were shown two words, such as “hand” and “apple,” from a list of 300 common nouns. A few seconds after, they were shown only one of the words, and then asked to remember its pair. Dr. Zaghoul’s team utilised the data from these tests to study how neural circuits in the brain store and replay memories.
Further results support the idea that more memorable words indicated high trafficked hubs in the brain’s memory networks. The epilepsy patients correctly recalled the memorable words quicker than the others.
Upon re-examining the test results, Dr. Xie and his colleagues found that patients successfully recalled some words more often than others, regardless of the order the words were paired. In fact, of the 300 words used, the five most recalled were on average about seven times more likely to be successfully remembered than the bottom five.
Initially, they found that rudimentary ideas could not explain their results. For instance, the more memorable words did not simply appear more often in sentences than the less memorable ones. Instead, their results suggested that the more memorable words happened to be more semantically similar, or more often linked to the meanings of other words used in the English language. When the researchers plugged semantic similarity data into the computer model, it more accurately guessed which words were more memorable from the test.
Further results support the idea that more memorable words indicated high trafficked hubs in the brain’s memory networks. The epilepsy patients correctly recalled the memorable words quicker than the others. Electrical recordings of the patients’ anterior temporal lobe, a language centre, showed that their brains replayed the neural signatures behind said words earlier than less memorable words. This strongly suggests that the more memorable words are so because they are easier for the brain to find.
Interestingly, both the patients and volunteers mistakenly called out the more memorable words more frequently than any other words. These results support previous studies which suggested that the brain’s process visits or passes through these highly connected memories, similar to how animals forage for food or we would browse the internet.
“You know when you type words into a search engine, and it shows you a list of highly relevant guesses? It feels like the search engine is reading your mind. Well, our results suggest that the brains of the subjects in this study did something similar when they tried to recall a paired word, and we think that this may happen when we remember many of our past experiences,” said Dr. Xie. “Our results also suggest that the structure of the English language is stored in everyone’s brains and we hope that, one day, it is used to overcome the variability doctors face when trying to evaluate the health of a person’s memory and brain.”