How the brain feels the time
Researchers from the Norwegian Institute of System Neurosciences. Kavli (Kavli Institute for Systems Neuroscience) discovered a network of brain cells that determine our sense of time in experiences and memories.
"This network provides time stamps for events and monitors the order of events in the experience", says Professor Edvard Moser, Nobel laureate and director of the Kavli Institute, which is located at the Norwegian University of Science and Technology (Norwegian University of Science and Technology , NTNU). The area of the brain that feels time is located in close proximity to the area responsible for the perception of space.
Expression of time
Hours are devices created by mankind to measure time. Agreeing with an unspoken social contract, we coordinate our own studies with hour time. However, our brain does not perceive the duration of time intervals in standard units - minutes and hours, as on your wristwatches. Temporary signatures in our experience and memories have completely different temporal characteristics.
In the course of evolution, living organisms, including humans, developed several biological clocks that help us keep track of time. The differences between different chronometers in the brain are not only in the time scale that they measure, but also in the phenomena to which the neural clock is tuned. Some chronometers are controlled by external processes: for example, circadian rhythms are tuned for sunrise and sunset. This watch helps the body to adapt to the day's rhythm.
Other chronometers are set by internal phenomena, like the hippocampal cells, which create a chain signal, like a domino effect, which quite accurately measures lengths of time up to 10 seconds. To date, we know most of the brain mechanisms used to measure time on a small scale (for example, in seconds). And, on the contrary, little is known about the time scale that the brain uses to record our experiences and memories that can last from a few seconds to minutes and hours.
Neuron clock for the lived time
A neural clock that tracks time in the course of the experience is exactly what was discovered, according to Albert Tsao and colleagues from the Kavli System Neuroscience Institute at NTNU.
By recording the activity of a population of brain cells, researchers identified deep within the brain a stable signal that codes for time.
"Our research reveals how the brain gives meaning to time as an event is experienced," Cao says, "This network does not code the time explicitly. What we measure is rather a subjective sensation of time, which is generated by the course of the events undergoing. "
The neural clock manages the organization of the flow of our experience into an orderly sequence of events. This activity generates in the brain hours for subjective time. Thus, the experience and sequence of events in it are the substance from which the brain generates and measures subjective time.
Temporary space and memory in the brain
"Today we have a pretty good understanding of how our brain perceives space, whereas our knowledge of time is not so complete," says Professor Moser.
"The space in the brain is relatively easy to explore. It consists of specialized cell types that are dedicated to specific functions. Together they form the basis of the system, "he added.
In 200? May-Britt and Edward Moser discovered neural grids that render our surroundings on different scales on a map consisting of hexagonal blocks. In 201? Moser shared the Nobel Prize in Physiology or Medicine for the discovery of cells that form a positioning system in the brain, with his colleagues and mentor John O'Keefe of University College London.
In 200? inspired by the discovery of the Moser of neural lattices encoding space, Albert Cao (at the time PhD candidate at the Kavli Institute) set himself the task of unraveling phenomena occurring in the mysterious lateral entorhinal cortex (LEC). This area of the brain is located near the medial entorhinal cortex (medial entorhinal cortex, MEC), where neural lattices were found by its leaders - Moser and others.
"I was hoping to find similar key active cells that would reveal the functional feature of this neural network," Cao says. This task resulted in a long-term project.
"It seemed that there was no pattern in the activity of these cells. The signal has been changing all the time, "says Moser's processor.
And only in the last couple of years the researchers began to assume that the signal is actually changing over time. Suddenly, the previously recorded data became meaningful.
This illustration shows an episodic time from an experienced 4-hour skiing from a steep mountain, including events that affected the time perception of a skier. The idea is that the lived time depends on the events and can be perceived faster or slower than the time on the clock.
A recently discovered record of the survived time is in the lateral entorhinal cortex (LEC) marked in green. Near the LEC is the MEC, the area of the brain responsible for spatial perception (not shown in the illustration). Next to the MEC is the hippocampus - a structure in which information from networks of time and space is combined to form episodic memories.
The rights to the image from NeuroscienceNews.com are owned by Kolbjørn Skarpnes & Rita Elmkvist Nilsen /NTNU Communication Division & Kavli Institute for Systems Neuroscience.
"Time is an unbalanced process. It's always unique and changeable, "says Moser's processor," If this network really encodes time, the signal must change over time so that experience is recorded as a unique memory. "
Moser and the company needed to decode the signal from only one neural array to find out how the space is encoded in the medial entorhinal cortex. Time interpretation in the lateral entorhinal cortex proved to be a much more difficult task. Only looking at activity in hundreds of cells, Cao and his colleagues could see that the signal encodes time.
"The activity in these neural networks is so distributed that the mechanism itself probably lies in the structure of the connections within these networks. The fact that it can take the form of various unique patterns implies a high degree of plasticity, "says Professor Moser," I believe distributed networks and combinations of structures of activity deserve special attention in the future. In this work, we found an area so closely related to the time of events or experiences that it could give rise to a whole new field of research. "
The form of time is
The structure of time has long been a topic of debate among philosophers and physicists. What is the recently discovered brain mechanism for incidental time can tell us how we perceive time? Is our perception of time linear, like the flow of a river, or cyclic, like a wheel or a spiral? The data from the Cavli studies say that both are true, and that the signal in the network coding for time can take many different forms, depending on the experience experienced.
In 201? PhD candidate Jørgen Sugar joined the Kavli project to conduct a new set of experiments that would test the hypothesis that the LEC network encodes a sporadic time. In one experiment, a wide range of experiments and variants of action was presented to the rat. She could run around freely, explore and chase after pieces of chocolate, visiting a series of open environments.
"The uniqueness of the time signal during this experiment suggests that the rat had a very good time record and a time sequence of events during the two-hour experiment," Sugar said. "We were able to use the signal from a time-coding network to accurately track when either Another event in the course of the experiment. "
In the second experiment, the problem was more structured, with a narrower spectrum of experiments and options for action. The rat was trained to chase the pieces of chocolate, turning left or right in an 8-maze.
"In this activity, we saw that the signal coding for time changed from unique sequences in time to a repetitive and overlapping pattern," Cao says. "On the other hand, the time signal has become more accurate and predictable in the course of repetitive tasks. The data suggest that the rat had a subtle sense of time during each round, but a poor sense of time from circle to circle and from beginning to end of the experiment. "
Professor Moser argues that the research shows that when you change the activity in which you are involved, when you change the contents of your experience, you actually change the time signals in the LEC, and thus how you perceive time.
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