The brain's GPS has a buddy system

January 11, 2018

To be successful as a social animal, you need to know where you stand relative to others. Brain cells that perform precisely this function--locating the 'self' and others in space--have now been identified. In rats, the same brain area that stores the animal's own location also maps the movements of other rats. Sometimes these representations are processed jointly by the same cells, depending on a rat's goals and actions. This discovery, from Japan's RIKEN Brain Science Institute, deepens our understanding of the hippocampus and its role as the brain's positioning system.

It has been known for some time that the hippocampus maintains a mental map of space--in fact, the 2014 Nobel Prize in Physiology or Medicine was awarded precisely for this research. 'Place cells' and 'grid cells' in the hippocampus register the location of the brain's owner in its environment, but until now, little was known about how the movements of others are tracked in the brain. Researchers put this to the test by observing the activity of hippocampal neurons in one rat (the 'self') watching another rat (the 'other') go through a simple T-maze. The self's neurons registered what the other was doing and changed their responses based on the self's location and subsequent actions. This study was published on January 11 in Science, which also contains a report of similar location awareness in the brains of bats.

Hippocampal place cells light up only for certain locations in the environment, and some of these cells clearly preferred the location of the other rat. Besides activation to places, the timing of neural activity in the hippocampus is also important. A 'refresh rate' of around 8 Hz dictates how often neurons update their activity, a phenomenon called theta-cycle phase precession. Three-quarters of cells updated based on the other's location, not only the self's. "It is very interesting that the trajectories of the other, that is, the past, current, and future positions of the observed rat, are compressively represented in 100-millisecond cycles in the hippocampus," says Shigeyoshi Fujisawa, research group leader at the RIKEN Brain Science Institute.

In two versions of the maze, the self-rat had to learn to visit the same T-arm as the other or the opposite arm. The majority of neurons were 'goal-focused', signaling the location of the goal, but a small number of neurons preferred the other's location regardless of whether it was on the same side as the goal. There were also cells that fired when either the other or the self were in specific spatial locations. "These cells are not confused," says Fujisawa. "We can reconstruct the paths of the pair of rats and reliably decode the location of the self or the other from the activity of these joint place cells."

Fujisawa and colleagues propose that the hippocampus has four different kinds of spatial models, one for the locations of the self, one for that of others, another for joint locations that are tuned relative to where the self and other are, and one for 'common' locations that activate when either the self or other are there (see image). This extends the existing cognitive map theory of how the hippocampus processes spatial locations and memories. "We think the cognitive map in the hippocampus is not just for knowing where the self is located," says Fujisawa, "but also for plotting the locations of other people, animals, or objects, and to comprehend the spatial environment surrounding the self."
-end-
Reference:

Danjo T, Toyoizumi T, Fujisawa S (2018) Spatial representation of self and other in the hippocampus. Science. doi: 10.1126/science.aao3898.

RIKEN

Related Neurons Articles from Brightsurf:

Paying attention to the neurons behind our alertness
The neurons of layer 6 - the deepest layer of the cortex - were examined by researchers from the Okinawa Institute of Science and Technology Graduate University to uncover how they react to sensory stimulation in different behavioral states.

Trying to listen to the signal from neurons
Toyohashi University of Technology has developed a coaxial cable-inspired needle-electrode.

A mechanical way to stimulate neurons
Magnetic nanodiscs can be activated by an external magnetic field, providing a research tool for studying neural responses.

Extraordinary regeneration of neurons in zebrafish
Biologists from the University of Bayreuth have discovered a uniquely rapid form of regeneration in injured neurons and their function in the central nervous system of zebrafish.

Dopamine neurons mull over your options
Researchers at the University of Tsukuba have found that dopamine neurons in the brain can represent the decision-making process when making economic choices.

Neurons thrive even when malnourished
When animal, insect or human embryos grow in a malnourished environment, their developing nervous systems get first pick of any available nutrients so that new neurons can be made.

The first 3D map of the heart's neurons
An interdisciplinary research team establishes a new technological pipeline to build a 3D map of the neurons in the heart, revealing foundational insight into their role in heart attacks and other cardiac conditions.

Mapping the neurons of the rat heart in 3D
A team of researchers has developed a virtual 3D heart, digitally showcasing the heart's unique network of neurons for the first time.

How to put neurons into cages
Football-shaped microscale cages have been created using special laser technologies.

A molecule that directs neurons
A research team coordinated by the University of Trento studied a mass of brain cells, the habenula, linked to disorders like autism, schizophrenia and depression.

Read More: Neurons News and Neurons Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.