How the Brain Processes Space and Time 

How does the human brain perceive time and space? These two dimensions are a fundamental part of our lives, yet surprisingly, not much is known about how the brain represents them. Researchers from SISSA’s Cognitive Neuroscience group have recently shed new light on this topic by discovering that the brain’s cortical areas for processing spatial and temporal information are organized according to a functional hierarchy. Their study was published in Nature Communications. 

They also show that time and space share the same populations of neurons that are used concurrently in posterior regions like the occipital cortex. In the anterior regions such as the frontal  cortex, there is a difference in the way space and time are processed independently, which allows  for the production of distinct “time maps.” The parietal cortex processes both time and space in varied ways between the two regions. 

Functional Hierarchy of the Brain in Space-Time  Processing 

As per the study, the brain is hierarchical in how it perceives time and space. Time and space are processed jointly in the occipital cortex of the posterior brain. A mix of independent and integrated processing modes is used in the parietal cortex of the intermediate brain. Time and space are  processed independently through different neural populations in the frontal cortex of the anterior brain. According to this hierarchy, after being intimately related in early visual areas, information travels toward higher-order cognitive regions progressively separated with time and space. 

The Experiment: Visual Stimuli in Different Screen  Positions 

In an experiment, participants were required to estimate the duration of time, a visual stimulus was present at different locations on a screen to study how people process space and time. High resolution fMRI scans of neural activity during this task helped identify the ways in which various  brain regions process spatial and temporal information. The results showed that space-time processing shifts from anterior regions’ distinct representations to posterior regions’ integrated coding.

Key Findings: Different Brain Areas, Different Processing  Strategies 

1. Posterior Cortex: Space and Time Processed Together 

The occipital cortex encodes space and time together while processing visual inputs. The same set of neurons that responds to the spatial location of an object also responds to the duration of the same object. In other words, the neurons were active with longer exposure. This means that space and time are processed by sharing common neural resources in early visual areas. 

2. Intermediate Cortex: A Transition Zone for Space-Time Processing 

The parietal cortex, an intermediate region in the brain’s hierarchy, showed a mix of processing mechanisms. Some neurons in this area responded to both spatial and temporal information, while others processed only one of these dimensions. 

The encoding of time in the parietal cortex varied: some neurons responded monotonically, similarly to those found in the occipital areas, while others were selective to certain durations and similar to patterns in the frontal cortex. Therefore, the parietal cortex is a bridging area from joint processing towards more specialized representations. 

3. Anterior Cortex: Separate Neural Populations for Space and Time 

In the frontal premotor cortex, the relationship between space and time was lost. Here, different  neural populations processed time independently of spatial location. Whereas in the occipital cortex, activity increased with longer durations, the frontal cortex created “time maps,” organized clusters of neurons responding selectively to specific durations. These results indicate that higher-order brain regions develop specialized mechanisms to handle time separately from space. 

Implications: Understanding Perception and  Neurological Disorders 

Human perception and daily function. Results of the study elucidate how motion, duration, and spatial location are represented with high accuracy during everyday behaviours such as crossing a street, playing sports, or estimating time intervals. In order to either merge or segregate spatial and  temporal information appropriately, various regions within the brain co-function.

Advancements in knowledge about cognitive and neurological disorders 

These findings could aid in understanding disorders like Parkinson’s disease, schizophrenia, or brain injuries, where time perception is often impaired. By identifying how different brain regions process time and space, researchers may develop targeted interventions for perceptual deficits in affected individuals. 

Future Directions: Expanding Space-Time Research Although this study provides significant insights, several questions remain:

• How do these processing mechanisms develop in children and change with aging?
• How does the brain integrate other sensory inputs, such as sound or touch, into space-time perception? 
• Can training or neuroplasticity modify how the brain processes time and space? 

Future research using advanced neuroimaging, computational modelling, and behavioural studies may further refine our understanding of space-time processing. 

Conclusion 

The study by Centanino, Fortunato, and Bueti advances our knowledge of how the brain processes  space and time, revealing a functional hierarchy in cortical regions. The occipital cortex processes  space and time together. The parietal cortex integrates or separates these dimensions variably. The  frontal cortex develops specialized neural populations for distinct durations. These findings not only  deepen our understanding of perception but also provide insights into cognitive functions, neural  disorders, and the intricate workings of the human brain.