Mapping verbal memory at birth
We have implemented a wireless setup that combines two brain imaging techniques, HD-DOT and EEG, along with a 3D registration method. HD-DOT is a cutting-edge technology that uses near-infrared light to create detailed maps of brain activity. By combining HD-DOT with EEG, we can gather both precise location information from HD-DOT and fast, real-time data from EEG. Additionally, we monitor heartbeat and breathing rates, along with video-based algorithms to assess infant behavior. This unique combination of methods helps us study brain activity related to speech, memory, brain plasticity, and sleep stages in newborns and infants.
So far, we tested and found evidence that only a few days after birth human infants can retain and recognize the sound of one word they have previously heard. The memory for the first words resists potential interference from other words pronounced by other speakers. However, we have also found that protracted consolidation periods are needed for the newborn brain to turn initial memory traces resistant to interference.
Phonological memory and the journey into its making in infancy
Because there was no existing test to measure phonological working memory in infants, we developed a new test called ADAM. This infant-controlled eye-tracking-based test allows us to see how well infants remember certain sound sequences and predict what will come next. The test adjusts its difficulty level based on how quickly each infant learns, making it personalized to each baby’s abilities.
In the first studies using the ADAM test, we looked at how many sound pieces or ‘chunks’ infants can hold in their memory for a short time. Our findings show that infants can handle both small (fewer than 3) and larger (more than 3 sounds) groups of syllables without any difficulty switching between them. This is different from how they process visual information, where infants tend to display strong limits in processing small and large number of items simultaneously. We think that being able to remember and work with groups of different sizes at once may help infants naturally process transient speech streams, allowing them to go beyond typical memory limits.
Phonological memory development in relation to linguistic skills, daily interactions and sleep
IN-MIND also tests the idea that early memory development is connected to environmental factors and language milestones in infants. To study this, we measured the language input that infants receive, their ability to understand and produce words, as well as their environment and sleep patterns.
Our early results show that infants with a stronger memory span also show better language skills. For example, babies with a higher memory span produced more vocal sounds compared to those with lower memory spans. We also found that sleep patterns—both night and day—are linked to differences in language skills and predict how they will evolve a few months later. Additionally, it seems that cultural factors like the number of adults who care for the child, and the quality of interactions with adults influence language development. This shows how important it is for infants to receive different kinds of language exposure from an early age.
