The hippocampus is a large region in the vertebrate brain that plays a key role in encoding navigation, memory and learning. Although much neuroscience has investigated the function and organization of this brain region, there is still much to discover.
Past research has consistently identified populations of cells in the hippocampus, generally known as time cells, that form temporal sequences essential for navigating in different environments and for episodic memory – remembering’ r past The ability to event is very important. The ability of these cells to generate temporal sequences is now well documented, but whether they represent collective experiences, or time itself, needs to be explored.
Recently, researchers from the Hebrew university in Jerusalem discovered that different populations of hippocampal cells encode time differently to themselves and others in their environment. The results of their study were published in theNature Neuroscience“Magazine.
Experiments with hardy Egyptian fruit bats reveal two distinct types of temporal cells
The research team said: Since any social behavior requires at least two different individuals to coordinate in space and time, and it is known from previous studies that time cells in the hippocampus (that is, compared to self-events, they will adapts to specific time cells) in the hippocampus to look for signs of time in other people seems reasonable. So the team carried out experiments on Egyptian fruit bats, highly social animals that thrive in different environments and are found in Africa, the Middle East, the Mediterranean and India.
In order to study the role of cells at different times, the researchers devised a new observational learning task. In this task, there were two observer bats and a display bat, and the observer watched the flight of the display and remembered its flight target. After the display bat returned to the starting point, the observing bat was taught to imitate its companion and fly to the same target for a reward.
The research team used small wireless devices to record and observe neural activity in the hippocampus of bats. To record the time cells, they looked at neurons in the hippocampus associated with observing the moment a bat lands, called classical time cells, with another moment of bat landing, called social time cells Activity . Temporal cells in CA1 bat hippocampus formed two distinct populations, and a population of temporal cells produced different time series when the bat was suspended at different positions. The team called the two types of hippocampal time cells “contextual” and “pure” time cells. Both can represent your own time, or other people’s time in a social setting. The researchers also discovered that “social time cells” encode temporal sequences that coincide with each other’s landing sites, and that these cells act as spatial and temporal coordination of self and others in social behavior.
The findings suggest that two different types of time cells exist, each using a different time code. “Contextual” time units can represent space and time in the same environment and support episodic memory; while “simple” time units encode only elapsed time. Finally, the researchers looked at “social” time cells, groups of cells in the mammalian brain that create temporal representations for peers and other people around the animal.
Research is helping to explain how the brain responds to specific events, perceives time, and coordinates with others
Together, the findings shed new light on the complex organization of the hippocampus, such as how the human brain encodes specific events from the past, detects intervals and supports coordination between itself and others. The findings contribute to the growing recent evidence that the hippocampal system can encode dimensions other than space, evidence that is not well reflected in current computational models of the hippocampal circuit, which may be resolved in studies in the future. The research team now plans to study how the hippocampus integrates spatial coding with other codes, such as social coding, among others.
Further reading: For the first time into the hippocampus to monitor blood oxygen concentration! Does Low Blood Oxygen Cause Alzheimer’s?
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1. https://www.nature.com/articles/s41593-022-01226-y
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