Summary: New study reveals a useful hierarchy in how the brain processes space and time. Space and time are strongly linked and processed by the same neurons in lateral areas, like the frontal cortex.
In front regions, such as the front brain, space and time are processed separately, with specific neuronal populations forming “time maps” for certain durations. Intermediate areas, like the frontal cortex, show mingled processing systems, bridging spatial and temporal integration.
This study provides new insights into how the mind integrates two important dimensions of human experience and reveals the distinctive coding strategies across cerebral regions.
Important Information:
- Posterior Cortex: Techniques space and time along, using shared neurological populations.
- Anterior Cortex: Separates space and time, forming different “time charts” for periods.
- Intermediate Cortex: Displays mixed running, integrating space and time variously.
Origin: SISSA
Imagine a cluster of flies, flickering lamps on and off in the nighttime storage. How is information about length and geographical position processed and incorporated by the human mind to enable this vision?
This was the issue addressed by Valeria Centanino, Gianfranco Fortunato, and Domenica Bueti from SISSA’s Mental Neuroscience class in their study published in Nature Communications.
The study demonstrates the existence of a practical pyramid in the human cerebral cortex, where lateral areas, which process sensory information first, process space and time separately.
In contrast, in frontal areas and even more so in front areas, engaged afterwards in information processing, space and time eventually split. Additionally, the way day is encoded varies across these brain regions.
Day is encoded in the exercise of the same neurological population in the frontal areas, where space and time are combined, which becomes proportionately more effective as the duration progresses.
In parietal and front areas, instead, where the link between space and time becomes increasingly weaker and finally disappears, time is encoded by specific neuronal populations, each of them responding deliberately to certain durations.
In the frontal areas, in an intermediate location of this pyramid, there is a coexistence of time and space that are either processed together or separately.
The Study: Physical Stimuli in Unique Screen Positions
How does the human brain’s perception of space change as well as its timeframe?
This was the issue driving the study.
The study’s authors claim that they wanted to know whether space and time are processed individually or not. Young, healthy participants were asked to evaluate the length of a sensory stimulus displayed at various positions on a display for varying amounts of time in order to create what might actually happen.
” Neuronal responses were recorded during this task using high-resolution spatial magnetic resonance imaging ( fMRI )” said the researcher.
Various Brain Areas, Different Programming Strategies. Posterior Cortex: Space and Time Processed Along
” What we discovered is that the relationship between space and time in the human mind is dynamic, not fixed, but rather depends on the brain regions at work. Because the same neurons process space and time, the connection is strong in the lateral region of our mind, especially in the occipital visual cortex.
” This place, specialized in receiving physical inputs, “explain Centanino, Fortunato, and Bueti”, responded to both the location and frequency of the signal: the longer the viewing time, the greater the brain activity in these neuron populations.”
Anterior Cortex: Separate Neurons for Space and Time
In the anterior regions, however, this connection disappears. In the frontal premotor areas, involved in movement preparation, time is processed independently of the position of the visual stimulus.
Different populations of neurons process time and space. Furthermore, the authors add”, duration is encoded differently compared to the posterior areas.
Here, distinct neural populations are contiguous in the cortical surface, forming what we might refer to as “time maps,” and distinct neural populations are preferentially responding to specific durations. “
Intermediate Cortex: A Variety of Mechanisms
The relationship between space and time is multifaceted in an intermediate region of this cortical hierachy, specifically the parietal cortex, which is functionally located between the occipital and frontal premotor cortex and is known for integrating various information sources.
The three researchers explain that some neuronal populations responded to the stimulus’s position and duration, while others only responded to one of these parameters.
” 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”.
A Functional Hierarchy in Time Processing
” This study”, conclude Centanino, Fortunato, and Bueti, “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.
According to the authors,” the existence of multiple response profiles to stimulus duration, along with their specific relationship to spatial processing, suggests that various brain areas each have a distinct role in the processing and perception of time.”
About this news about neuroscience research
Author: Donato Ramani
Source: SISSA
Contact: Donato Ramani – SISSA
Image: The image is credited to Neuroscience News
Original Research: Open access.
Valeria Centanino and colleagues ‘” The neural connection between the human visual hierarchy’s spatial and stimulus duration” Nature Communications
Abstract
The neural connection between the human visual hierarchy’s spatial and stimulus duration
Our sensory experience requires the integration of spatial and temporal information. Although psychophysical research suggests that duration perception depends on spatial factors, few studies have directly examined the neural connection between temporal and spatial processing.
We investigated how and where the processing and the representation of a visual stimulus duration is related to that of its spatial location using ultra-high-field functional MRI and neuronal-based modeling.
Our results show a transition in duration coding: from monotonic and spatially-dependent in early visual cortex to unimodal and spatially-invariant in frontal cortex.
Along the dorsal visual stream, particularly in the intraparietal sulcus ( IPS), neuronal populations exhibit common, selective responses to both spatial and temporal information.
In the IPS, spatial and temporal topographic organizations are also linked, although duration maps are smaller, less clustered, and more variable across participants.
These findings help to identify the mechanisms that control how visual duration is perceived by humans and highlight the crucial role that time and space play in shaping brain responses.
