The role of daydreaming in memory formation and learning

Daydreaming may help shape the brain, study suggests

The Week, December 15, 2023 : A recent study conducted on mice has shed light on what happens in the brain while daydreaming, offering intriguing insights into the potential role of daydreams in brain plasticity. The research observed the activity of neurons in the visual cortex of mice while they were in a quiet waking state. The findings indicated that the mice's brain activity resembled patterns that occurred when they were actually looking at an image, suggesting that they were daydreaming or thinking about the image. Moreover, the patterns of activity during their initial daydreams predicted how the brain's response to the image would change over time.

This study, led by Harvard Medical School, provides early evidence that daydreams may have an impact on the brain's ability to adapt and remodel itself in response to new experiences. The researchers aimed to understand the neurobiological process of daydreaming and determine whether these moments of quiet reflection play a role in learning and memory.

Scientists have extensively studied how neurons replay past events to form memories and navigate spatial environments in the hippocampus, a brain region crucial for memory. However, little research has been done on the replay of neurons in other brain regions, including the visual cortex, which is responsible for visual memories.

By recording the activity of around 7,000 neurons in the visual cortex, the researchers discovered that when mice looked at an image, the neurons fired in a distinct pattern that differentiated one image from another. Surprisingly, when the mice looked at a gray screen between images, the neurons sometimes fired in a similar pattern to when they were looking at the image, indicating that the mice were daydreaming about the image. These daydreams occurred when the mice were relaxed, exhibiting calm behavior and small pupils.

The researchers also observed that the activity patterns associated with the images changed throughout the day and over time, a phenomenon known as "representational drift." Interestingly, the pattern observed during a mouse's initial daydreams about an image predicted how the pattern would evolve when the mouse looked at the image later.

Additionally, the study revealed that daydreaming in the visual cortex occurred simultaneously with replay activity in the hippocampus, suggesting communication between the two brain regions during these daydreams.

The researchers speculate that daydreams may actively contribute to brain plasticity. By differentiating between two images seen repeatedly, daydreaming might guide the neural patterns associated with each image away from each other, ultimately enhancing the mouse's ability to respond more specifically to each image in the future.

These findings align with previous research showing that entering a state of quiet wakefulness after an experience can improve learning and memory in both rodents and humans.

The researchers emphasise the importance of allowing moments of quiet wakefulness that lead to daydreams. For mice, this means taking breaks from looking at a series of images, while for humans, it could involve stepping away from constant smartphone scrolling. Creating space for these daydreaming events may be crucial for promoting brain plasticity.