GUESS WHAT HAPPENS NEXT: How our brain uses patterns in the world to make predictions!
Two fundamental activities that the brain does are 1) pick up on patterns and 2) make predictions.
As we navigate the world, we pick up on patterns in the information that we perceive. For example, when you listen to your favourite song you may be sensitive to the regularity of the drum beat and surprised by a sudden beat drop! That feeling occurs because your brain is sensitive to the patterns in the music and is surprised when the pattern that you thought would continue is interrupted.
In the laboratory, scientists have studied the brain’s ability to pick up on patterns by recording the brain’s activity as participants listen to spoken language. Scientists have observed that when we listen to speech, the brain's activity synchronizes with the rhythm of the syllables being spoken. Like when you find yourself tapping along to the beat of your favourite song, the brain also registers rhythmic patterns in natural language. This kind of synchronization happens without conscious effort. Whether you’re listening to music or overhearing a conversation in another language, your brain is automatically tuning in to the regularity of the syllables or the sounds that you are being exposed to. Synchronization of brain activity to events in the world is called neural entrainment.
Monitoring neural entrainment is an exciting (and relatively recent) advance in the neuroscientific field. Neural signalling (the way the brain talks to itself) is electrical, and through the use of very sensitive electrodes, we can listen in to this electrical activity. Based on these recorded patterns of activity, scientists can make inferences about what the brain is doing. To monitor neural entrainment, scientists carefully monitor the timing of events in the world. Then, they look for brain signals that match in timing with the external events, indicating the brain is tracking these patterns.
As the brain tracks these patterns of information, something interesting happens; the brain starts to group the patterns as ‘words’ within the stream of sounds. Since certain syllables are more likely to follow and other syllables are unlikely to follow, the brain treats sets of likely syllables as words, and unlikely pairs as breaks between words. As we learn these words, the brain starts to entrain not only at the syllable level but at the world level as well. This means that the brain makes predictions not only based on sensory features, but also meaningful units like words, pictures, or concepts. When this kind of learning occurs, scientists observe neural entrainment to words as well as syllables. This procedure has been used in several labs around the world as evidence that the brain cares about the patterns around us.
So, neural entrainment studies show us that the brain is sensitive to patterns of information. And as we learn, the type of information with which the patterns are built can change! Scientists (Dr. Laura Batterink, and her students Mulgrew and Gibbings) asked in their paper whether entrainment actually helps the brain in its second important job: making predictions about the world around us. To do this, Batterink’s lab had to develop a novel procedure to manipulate neural entrainment. They reasoned that if neural entrainment was used by learners to help them make predictions about the world, then somehow boosting neural entrainment should lead to improvements in these predictions.
Batterink had participants listen to a string of syllables that sounded like non-sense. For example, they might hear something like: BA-DA-RA-BA-DA-MA-DA-BA-DA (try reading this out-loud to get the full effect). Although the participants felt like they were listening to nonsense, the string of syllables is actually very carefully constructed. For instance, if you study the above speech stream, you’ll notice that the syllable DA always follows after the syllable BA. Thus, when the participant hears BA they could reasonably expect the next syllable to be DA. This is a simplification of the procedure, the syllables that the participants were exposed to were organized in a way that was more complex.
Behavioural results show that participants register the probabilities of a specific syllable coming next and make better (faster) predictions for syllables that are more expected.
Figure 1: This image shows the synchronous condition in which the water drops fell at the same time as the words in the syllable stream. This was found to increase neural entrainment and helped participants make predictions about upcoming syllables.
The novel innovation that Batterink’s team added to their procedure was to add a video which was presented at the same time as the audio stream. While the participant listened to a string of syllables (like the one presented earlier) they also watched one of two videos of water dropping from a leaf. Critically, in each of the videos the drops of water fell at specific times. In one video the water drops fell in synch with the words in the recording, in the other video, the water was not synchronized to the words.
The authors found that seeing the water drops at the same time as the speech syllables BOOSTED neural entrainment.
This must have been an exciting demonstration for Batterink’s team, but they were not finished yet. Their goal was to determine if neural entrainment boosted the brain's ability to make predictions about the input. Now that they had built a condition in which they could enhance neural entrainment, they were able to compare learners with higher and lower entrainment and see if these participants were different in how they made predictions about what should come next in the speech stream. To test this, participants listened to the speech stream again, this time with the task of pressing a response key any time a specific syllable appeared. If participants are making better predictions about what comes next in the speech stream, they should be faster to respond to the target syllable (because they can anticipate that it is coming next!). Indeed, Batterink’s team found that participants in the high neural entrainment group showed better (faster) predictions than in the other entrainment conditions.
Overall, these findings demonstrate that better entrainment leads to better predictions. The brain is finely tuned to the patterns around us, and this research suggests that the brain uses its knowledge about these patterns to make predictions about what is coming next. This study was able to monitor in real time two important fundamental properties of the brain: its sensitivity to regularity, and its capacity for prediction.
So, when you’re listening to music and you jump at the sudden bass drop, you’re experiencing a real-life example of entrainment and prediction at work. These same processes may also support many other important behaviours, like learning a new language. One exciting direction for Batterink and her team is to test whether strengthening entrainment can make second-language learning easier. They predict that since neural entrainment helps listeners understand which units make up words, and when the breaks between words occur, higher neural entrainment might improve language learning. If so, these insights would not only advance neuroscience but could also shape practical tools for education. In other words, your brain’s remarkable ability to guess what happens next might be the key to learning, communication, and adaptation in everyday life.
Original Article: Batterink, L. J., Mulgrew, J., Gibbings, A. (2024). Rhythmically Modulating Neural Entrainment during Exposure to Regularities Influences Statistical Learning. Journal of Cognitive Neuroscience, 36(1): 107-127.