- Some words may be inherently easier for our brains to recall than others
- To understand this phenomenon, a team of scientists studied epileptic patients and healthy individuals
- The results of the study could help professionals evaluate patients' brain health
The brain is one of the most fascinating organs of the human body. Discoveries about the brain include the fact that its storage capacity is virtually unlimited; that it can generate around 23 watts of power (enough to power a lightbulb); and that it can survive for up to six minutes without oxygen.
In a more recent discovery, National Institutes of Health researchers gained some insight into why our brains remember certain words much better than others. The study focused on epilepsy patients and healthy volunteers and was published in Nature Human Behaviour.
Taking it a step further, the team combined memory tests, brain wave recordings, and surveys of billions of words published in books, news articles and internet encyclopaedia pages, and showed how the organ may recall words, in addition to memories of our past experiences.
How the brain controls memory
So how is it that some words are more memorable than others? According to Weizhen Xie, a cognitive psychologist and post-doctoral fellow at the NIH's National Institute of Neurological Disorders and Stroke (NINDS), and lead author of the study, their results support the idea that our memories are wired into "neural networks", and that our brains search for these memories much the same way search engines search for information on the internet.
The team reanalysed the results of memory tests from 30 epilepsy patients who were part of a clinical trial led by Dr Kareem Zaghloul, a neurosurgeon and senior investigator at NINDS. Zaghloul and his colleagues try to help epileptic patients whose seizures can’t be controlled by drugs (known as intractable epilepsy).
The observation period for these patients included spending a number of days at the NIH's Clinical Center with surgically implanted electrodes. The electrodes are designed to detect changes in patients’ brain activity.
Top five words
Patients were shown pairs of words, including "hand" and "apple", from a list of 300 common nouns. A few seconds later they were shown one of those words again and asked to remember its partner. This was used to study how neural circuits in the brain store and replay memories.
Xie and his team reexamined these test results and found that the patients recalled some words more often than others, irrespective of the pairings. More than this, of the 300 words used, the top five words were, on average, more than five times more likely to be successfully recalled than the bottom five.
Similar results were seen after 2 623 healthy volunteers took an online version of the word pair test. Zaghloul commented: "We saw that some things – in this case, words – may be inherently easier for our brains to recall than others.
"These results also provide the strongest evidence to date that what we discovered about how the brain controls memory in this set of patients may also be true for people outside the study."
Current results support previous studies
The more memorable words represented "high trafficked hubs" in the brain's memory networks. The authors explained that electrical recordings of the patients' anterior temporal lobe (a language centre), showed that their brains replayed the neural signatures behind those words earlier than the less memorable ones, which they believe means that the more memorable words are easier for the brain to find.
In addition to this, they also found that all participants mistakenly called out the more memorable words more often than the other words. These results support previous studies, the authors wrote, which suggests that the brain may "visit" or pass through these highly connected memories, in much the same way as a computer searches 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 Xie, concluding:
"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."
Zaghloul also commented: “If we can predict what people should remember in advance and understand how our brains do this, then we might be able to develop better ways to evaluate someone's overall brain health.”