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A groundbreaking study led by Valeria Centanino, Gianfranco Fortunato, and Domenica Bueti from the Cognitive Neuroscience group at SISSA sheds new light on how the human brain processes space and time. Published in Nature Communications, the research explores the intricate relationship between these two essential elements of our perception.
Imagine a swarm of fireflies flickering in the night sky—each light not only occupies a position in space but also has a duration. How does the human brain make sense of these two dynamic features? This was the core question that the research aimed to address.
Functional Hierarchy of Space and Time Processing
The study revealed that the brain processes space and time in a hierarchical manner, with posterior areas of the cerebral cortex integrating both dimensions, while areas further along in the processing chain—specifically the parietal and frontal regions—begin to treat them more independently.
In the occipital cortex, which handles initial visual processing, space and time are linked and encoded by the same neural populations. The research found that the longer the visual stimulus is presented, the more active these neurons become, reflecting both spatial and temporal information together.
However, as the information moves forward through the brain, particularly in the parietal and frontal regions, the connection between space and time weakens. In these regions, distinct neural populations become responsible for processing either space or time, with the encoding of duration becoming more specialized.
Experiment: Judging Duration and Space on a Screen
To investigate these relationships, the researchers conducted an experiment in which participants were asked to judge the duration of a visual stimulus presented at different positions on a screen. The stimulus varied in duration, and the researchers recorded neural responses using high-resolution spatial magnetic resonance imaging (fMRI).
In the occipital cortex, space and time were processed by the same neural populations, meaning that the activity of these neurons increased proportionally to the duration of the stimulus. In contrast, the frontal premotor areas responsible for movement preparation showed distinct neural populations for space and time processing.
The Parietal Cortex: A Bridge Between Regions
The parietal cortex, known for integrating various types of information, was found to occupy an intermediate position in the hierarchy. Some neurons in this region responded to both space and time, while others responded only to one or the other. The researchers discovered that, similar to the occipital cortex, some neurons in the parietal cortex encoded time monotonically, while others showed specific preferences for particular durations, akin to the time encoding observed in the anterior areas.
Implications for Understanding the Brain’s Processing of Time
The study’s findings contribute significantly to our understanding of how the brain perceives and integrates space and time. It suggests that different areas of the brain contribute in unique ways to the processing and perception of these fundamental aspects of our reality. The presence of distinct neural populations for encoding space and time highlights the brain’s ability to organize and prioritize these dimensions in different contexts.
As the researchers conclude, “The existence of multiple response profiles to stimulus duration, along with their specific relationship to spatial processing, suggests that different brain areas contribute distinctly to the processing and perception of time.”
For further details, the full study is published in Nature Communications (DOI: 10.1038/s41467-024-54336-5).
Disclaimer: The findings presented in this article are based on a scientific study and may not represent the opinions of all researchers in the field. Further research is needed to explore the full implications of these discoveries.
