How time and space interact in the brain

Have you ever tried to catch a baseball? In that split second, your brain is doing something remarkable – it’s tracking both where the ball is and how long it’ll take to reach you. This everyday feat of coordination reveals an extraordinary truth about our brains: they’re constantly processing time and space simultaneously.

Scientists have long wondered exactly how our brains juggle these two fundamental aspects of reality. Now, researchers from SISSA‘s Cognitive Neuroscience group have cracked open this mystery.

In their study, Valeria Centanino, Gianfranco Fortunato, and Domenica Bueti revealed an elegant system at work in our brains.

The findings show that different brain regions process time and space in unique ways – much like a company where some departments handle multiple tasks together, while others specialize in just one thing.

A functional hierarchy in the brain

The study found that posterior brain regions, which first receive visual information, process time and space together. As information moves forward to the parietal and frontal areas, these two elements gradually separate.

Moreover, the way time is encoded varies across brain regions. In the occipital areas, space and time are processed together, with the same neural population encoding both aspects. The longer the duration of a stimulus, the more active these neurons become.

However, in the parietal and frontal areas, time is processed by separate neural populations – each responding selectively to specific durations. The parietal cortex serves as an intermediary, and contains mechanisms that process time both in conjunction with space and separately.

Understanding this hierarchy sheds light on how the brain organizes information about time and space as it helps us to interact with our environment.

Whether we are tracking a moving object, estimating the length of an event, or synchronizing actions, these brain mechanisms play a crucial role in perception and behavior.

Brain’s perception of space and time

The researchers sought to answer a fundamental question: how does the human brain process visual information that changes in both spatial position and duration? “We wanted to understand whether space and time are processed independently or not,” the authors explained.

To explore this, the team conducted an experiment with young, healthy participants. Subjects were asked to judge the duration of a visual stimulus that appeared in different screen positions for varying amounts of time.

During this task, neural activity was recorded using high-resolution functional magnetic resonance imaging (fMRI). This technique allowed the researchers to map how different brain areas responded to analysis of space and time, which provided insights into the underlying neural mechanisms.

The results confirmed that different brain regions follow distinct strategies for encoding space and time. Some areas integrate the two aspects, while others treat them as separate dimensions.

This finding challenges the notion of a fixed processing method and instead suggests a dynamic system that adapts based on functional needs.

Unified processing of time and space

One of the most striking findings of the study was that in the occipital visual cortex, space and time are processed together. This region, located at the back of the brain, is responsible for receiving and interpreting visual stimuli. It plays a crucial role in detecting motion, object positions, and duration.

“What we discovered is that the link between space and time in the human brain is not fixed but depends on the brain areas involved. In the posterior part of our brain, particularly in the occipital visual cortex, the connection is strong because space and time are processed by the same neurons,” noted the researchers.

Neurons in this region responded to both the position and duration of the visual stimulus. The longer the viewing time, the greater the brain activity in these neuron populations. This suggests that in early visual processing, space and time are closely intertwined, and form a unified representation.

This integration is essential for motion perception, as it allows the brain to track moving objects and estimate their speed and direction.

Separate processing of time and space

As information moves forward in the brain, the connection between space and time weakens. In the frontal premotor areas, which are involved in movement planning and decision-making, time is processed independently of spatial position. Here, distinct neural populations encode time and space information separately.

“Duration is encoded differently compared to the posterior areas. Here, distinct neural populations preferentially respond to specific durations, and neural populations that prefer similar durations are contiguous in the cortical surface, forming what we might call ‘time maps,’” the researchers explained.

Unlike in the occipital cortex, where neurons show a proportional increase in activity with longer durations, the frontal cortex operates with a categorical system.

Specific groups of neurons respond to specific time intervals, suggesting a more structured and segmented approach to time perception. This organization may help in tasks that require precise timing, such as motor planning, coordination, and anticipation of future events.

The parietal cortex: A transition zone

Between the occipital and frontal regions lies the parietal cortex, which serves as a transition zone for processing space and time. This area is known for integrating multiple sources of information and plays a role in attention, perception, and cognitive functions.

“Some neuronal populations responded to both the position and the duration of the stimulus, while others responded only to one of these dimensions. The response to time was, in some cases, monotonic, like in the occipital cortex, while in others it showed selectivity for specific durations, similar to the anterior areas,” the authors noted.

This finding suggests that the parietal cortex contains a mix of processing strategies. Some neurons continue to encode space and time information together, while others start to specialize in one aspect only. This flexibility allows the brain to adapt to different perceptual demands.

For instance, when focusing on a moving object, integrated processing may be more beneficial. However, when making a precise timing judgment, a more specialized representation of time may be required.

Understanding time perception

The study offers a new perspective on how the brain perceives time. Rather than having a single mechanism to governing time processing, multiple strategies coexist, with each serving a different function. Some brain regions maintain a close relationship between space and time, while others progressively separate them.

“This study advances our understanding of how space and time, two fundamental aspects of our experience of the world, are processed and integrated in the human brain. Moreover, it sheds light on the presence of a functional hierarchy in time processing,” concluded the researchers.

By identifying the distinct roles played by different brain regions, this research provides valuable insights into cognitive neuroscience. The study may also have implications for understanding disorders that affect time perception, such as Parkinson’s disease, schizophrenia, and certain neurological conditions.

Future of space-time research

The discovery of a functional hierarchy in time processing raises new questions about the brain’s adaptability.

If space and time are processed differently depending on the brain region, how does this system respond to changes, such as learning, injury, or aging? Future research could explore whether these mechanisms can be trained or modified through experience.

Additionally, understanding how the brain encodes time may help in developing new technologies for artificial intelligence, robotics, and virtual reality. By mimicking the brain’s ability to process space and time data, engineers could create more responsive and adaptive systems.

This study offers a deeper look into the intricate workings of the human brain. By mapping the neural circuits that handle space and time perception, researchers continue to unravel the complexities how we experience the world.

The study is published in the journal Nature Communications.

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