How a mind encodes time and place

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This picture shows entorhinal

This picture shows entorhinal “ocean cells” (red) and “island cells” (blue). Green shimmer indicates sea cells that have been genetically altered.

Neuroscientists brand a mind circuit that is vicious for combining episodic memories

When we remember a sold experience, that memory has 3 vicious elements — what, when, and where. MIT neuroscientists have now identified a mind circuit that processes a “when” and “where” components of memory.

This circuit, that connects a hippocampus and a segment of a cortex famous as entorhinal cortex, separates plcae and timing into dual streams of information. The researchers also identified dual populations of neurons in a entorhinal cortex that communicate this information, dubbed “ocean cells” and “island cells.”

Previous models of memory had suggested that a hippocampus, a mind structure vicious for memory formation, separates timing and context information. However, a new examine shows that this information is separate even before it reaches a hippocampus.

“It suggests that there is a dichotomy of duty upstream of a hippocampus,” says Chen Sun, an MIT connoisseur tyro in mind and cognitive sciences and one of a lead authors of a paper, that appears in a Sept. 23 emanate of Neuron. “There is one pathway that feeds temporal information into a hippocampus, and another that feeds contextual representations to a hippocampus.”

The paper’s other lead author is MIT postdoc Takashi Kitamura. The comparison author is Susumu Tonegawa, a Picower Professor of Biology and Neuroscience and executive of a RIKEN-MIT Center for Neural Circuit Genetics during MIT’s Picower Institute for Learning and Memory. Other authors are Picower Institute technical partner Jared Martin, Stanford University connoisseur tyro Lacey Kitch, and Mark Schnitzer, an associate highbrow of biology and practical production during Stanford.

When and where

Located only outward a hippocampus, a entorhinal cortex relays feeling information from other cortical areas to a hippocampus, where memories are formed. Tonegawa and colleagues identified island and sea cells a few years ago, and have been operative given afterwards to learn their functions.

In 2014, Tonegawa’s lab reported that island cells, that form tiny clusters surrounded by sea cells, are indispensable for a mind to form memories joining dual events that start in quick succession. In a new Neuron study, a group found that sea cells are compulsory to emanate representations of a plcae where an eventuality took place.

“Ocean cells are critical for contextual representations,” Sun says. “When you’re in a library, when you’re channel a street, when you’re on a subway, we have opposite memories compared with any of these contexts.”

To learn these functions, a researchers labeled a dual dungeon populations with a fluorescent proton that lights adult when it binds to calcium — an denote that a neuron is firing. This authorised them to establish that cells were active during tasks requiring mice to distinguish between dual opposite environments, or to couple dual events in time.

The researchers also used a technique called optogenetics, that allows them to control neuron activity regulating light, to examine how a mice’s function altered when possibly island cells or sea cells were silenced.

When they blocked sea dungeon activity, a animals were no longer means to associate a certain sourroundings with fear after receiving a feet startle there. Manipulating a island cells, meanwhile, authorised a researchers to widen or digest a time opening between events that could be related in a mice’s memory.

Information flow

Previously, Tonegawa’s lab found that a banishment rates of island cells count on how quick a animal is moving, heading a researchers to trust that island cells assistance a animal navigate their approach by space. Ocean cells, meanwhile, assistance a animal to commend where it is during a given time.

The researchers also found that these dual streams of information upsurge from a entorhinal cortex to opposite tools of a hippocampus: Ocean cells send their contextual information to a CA3 and dentate gyrus regions, while island cells plan to CA1 cells.

Tonegawa’s lab is now posterior serve studies of how a entorhinal cortex and other tools of a mind paint time and place. The researchers are also questioning how information on timing and plcae are serve processed in a mind to emanate a finish memory of an event.

“To form an episodic memory, any member has to be recombined together,” Kitamura says. “This is a subsequent question.”

Source: MIT