Apart from sleep, which promotes learning, our brain takes between one and two hours to learn a new word.
- Each word has two aspects: a phonetic model and semantics.
- Attaching a meaning to an invented word makes it easier to learn.
- It is the cortical activity of the brain that is modified when learning a new word.
The neurocognitive mechanisms of learning are poorly understood. To try to see more clearly, Russian researchers monitored changes in brain activity associated with learning new words. They found that representations in the brain of the sound and meaning of these words can be formed within just one to two hours of seeing or reading them for the first time, without a period of sleep. They published their results on September 11 in the journal Frontiers in Neuroscience.
A pioneering study
This discovery was not easy because each word has two aspects: a phonetic model and semantics. “To understand the mechanism of word learning, it is necessary to study these two aspects: an original phonetics, that is to say that the word must not be constructed from known roots or other morphemes, and it must acquire an original meaning, i.e. not be synonymous with a known wordsays Alexandra Razorenova, co-author of the paper, and researcher at the Skolkovo Institute of Science and Technology (Skoltech). These restrictions are quite difficult to satisfy and control in an experimental setting. The second difficulty is the separation of sematic and phonological processes because they overlap in time and brain location. Finally, designing an effective learning procedure that engages the participant’s brain is another challenge..”
The researchers looked for evidence on how the brain learns both a phonological representation of a new word (how it sounds) and its meaning, or the semantic aspect of acquiring a new word. They were also looking for what is called rapid cortical plasticity, that is, the immediate changes in brain activity that follow learning a new word. No previous study has been able to do this. For this, they used magnetoencephalography (MEG) to observe how 24 participants in the experiment learned eight Russian words invented for the study. A participant had to associate four of these words with the movements of the hand and foot to make sense of them.
A memory familiarization mechanism
The results showed immediate changes in cortical activity in word learning. The research team also showed that these changes are significantly different for words that have an imagined meaning and those that do not. “The contrast between the neural responses elicited by the empty ‘pseudo-words’ and those that have them has made it possible to locate the semantic network and the relationship between sematic and phonological learningreported Alexandra Razorenova. This semantization facilitates or even triggers the reinforcement of the cortical network that underlies the phonological aspect of lexicality. In other words, significant ‘pseudo-words’ acquire priority to be recognized and memorized.”, concludes the researcher.
Scientists hypothesize that this is because the deep familiarization with word forms during the experiment completely changed the repetition effect: instead of increasing neural responses to previously unfamiliar word forms, she diminished them. “The above considerations suggest that our findings most likely reflect a memory familiarization mechanism that, once formed, lasts for several days.”, suggests the researcher. The latter believes that this could be useful for the diagnosis of speech disorders since researchers are now able to differentiate disorders of phonological processes from the failure of the sematic network. “In a broader perspective, our results highlight the crucial role of interactive learning compared to passive learning procedures widely used in the literature.”, continues Alexandra Razorenova.
