Time flows as a constant stream of moments, but your brain sees patterns in this flow. Now, scientists have discovered exactly how individual neurons learn to recognize and predict these patterns, providing the first direct evidence of how our brains map out the structure of time.
The study, published in Nature, was conducted by researchers at UCLA Health. It required recording the activity of individual neurons in patients who had electrodes implanted in their brains for epilepsy treatment. These recordings offer a rare glimpse into how individual brain cells behave during learning and memory formation—something that’s impossible to observe with standard brain imaging techniques.
“Recognizing patterns from experiences over time is crucial for the human brain to form memory, predict potential future outcomes, and guide behaviors,” says Dr. Itzhak Fried, director of epilepsy surgery at UCLA Health, in a statement. “But how this process is carried out in the brain at the cellular level had remained unknown – until now.”
Prior to the main experiment, researchers needed to identify which images would trigger strong neural responses in each participant. They showed participants about 120 different pictures over 40 minutes, including images of celebrities, landmarks, and other subjects chosen partly based on each person’s interests. Based on how brain cells responded, researchers selected six specific images for each participant to use in the main experiment.
The main study had three phases. In the first phase, images appeared in random order while participants performed simple tasks, like identifying whether the person shown was male or female. During the middle phase, images appeared in sequences that followed specific rules, though participants weren’t told about these rules. Instead, they focused on a new task: determining whether each image was shown normally or in a mirror image. The final phase returned to random sequences and the original gender identification task.
The sequence rules were based on what researchers called a pyramid graph. Six points were arranged in a triangle shape, with each point representing one of the selected images. Lines connected certain points, indicating which images could appear after others. Some images were directly connected, like neighboring points on the graph. Others required taking an indirect path through multiple points to get from one to another.
What makes this study particularly fascinating is that it revealed how individual neurons adapted as participants became familiar with these sequences. At first, a neuron would respond strongly to just one specific image. But over time, these same neurons began responding to images that frequently appeared close together in the sequence, essentially mapping out the temporal relationships between different images.
The brain’s ability to encode these temporal patterns shares remarkable similarities with how it represents physical space. Previous research discovered that certain neurons act as “place cells,” firing when an animal reaches specific locations, while others function as “grid cells” that help measure distances. The new study shows the brain uses comparable mechanisms to map out sequences of events and experiences.
This research also builds on earlier discoveries about “concept cells,” neurons that respond to specific individuals, places, or objects. These specialized brain cells appear to be fundamental building blocks of memory. The new findings show how these neurons work together to create structured representations of our experiences through time.
The researchers discovered that this neural mapping created what they call a “successor representation,” a predictive map that considers not just immediate connections but likely future events. Rather than simply linking one moment to the next, your brain builds a broader model of likely future possibilities based on learned patterns.
“This study shows us for the first time how the brain uses analogous mechanisms to represent what are seemingly very different types of information: space and time,” explains Fried. “We have demonstrated at the neuronal level how these representations of object trajectories in time are incorporated by the human hippocampal-entorhinal system.”
During breaks between testing phases, researchers observed “replay” events, moments when neurons would rapidly rehearse the learned sequences in a compressed timeframe. This neural replay happened in milliseconds, suggesting a mechanism for consolidating learned patterns into memory.
Understanding how the brain encodes temporal patterns goes beyond basic science. The findings could help develop new treatments for memory disorders and advance the design of brain-computer interfaces. They may also inform artificial intelligence systems that aim to process sequential information in ways that mirror human cognition.
Source : https://studyfinds.org/brain-experiences-sense-of-time/