Neurons in the rat brain use a preexisting set of firing sequences to encode future navigational experiences

July 25, 2013
Figure 1: The firing of temporal sequences of place cells in rats during sleep encodes for future spatial trajectories. Credit: George Dragoi and Susumu Tonegawa, RIKEN–MIT Center for Neural Circuit Genetics

Specialized neurons called place cells, located in the hippocampus region of the brain, fire when an animal is in a particular location in its environment, and it is the linear sequence of their firing that encodes in the brain movement trajectories from one location to another. Building on previous work, George Dragoi and Susumu Tonegawa from the RIKEN–MIT Center for Neural Circuit Genetics have now shown that place cells have a preexisting inventory of firing sequences that they can use to encode multiple novel routes of exploration1.

Specific sequences of are known to encode spatial experiences, but it has been debated whether such sequences are formed during a new experience or preformed and adapted to specific experiences when required. Dragoi and Tonegawa recently showed that 'future' place cells fire in sequence while the animal is asleep, prior to experiencing a novel environment, and that animals use this preexisting neuronal firing pattern to rapidly learn how to navigate their surroundings.

To confirm and investigate this mechanism further, the researchers first recorded the of place cells in rats during one hour of sleep. Next, they monitored this activity during movement along a track that the rat had not previously explored, and later recorded it during movement along the same track with two additional lengths separated by right-angle turns. They then correlated the temporal pattern of place cell activity recorded during sleep with the spatial pattern of activity recorded while the animals were freely exploring the longer track.

The researchers found that the sequences of place cell activity were unique for each of the three lengths of the track and matched those recorded during sleep (Fig. 1). "We had observed the same sequences as independent clusters of correlated temporal sequences during the preceding sleep period," explains Dragoi. 

The results suggest that rapid encoding of particular trajectories within novel environments is achieved during exploration by selecting from a set of preexisting temporal sequences that fired during sleep. In other words, hippocampal place cells appear to be prearranged into sets of sequential firing cells that can be adapted rapidly to encode for multiple spatial that the animal could undertake in its surroundings. Based on their data, Dragoi and Tonegawa predict that the sets of hippocampal place cells could encode for at least 15 unique future spatial experiences. In addition, their findings could explain the role that the hippocampus plays in humans in imagining future encounters within our own complex environment.

Explore further: Mapping blank spots in the cheeseboard maze

More information: Proceedings of the National Academy of Sciences USA 110, 9100–9105 (2013). DOI: 10.1073/pnas.1306031110

Related Stories

Mapping blank spots in the cheeseboard maze

March 22, 2013
(Medical Xpress)—During spatial learning, space is represented in the hippocampus through plastic changes in the connections between neurons. Jozsef Csicsvari and his collaborators investigate spatial learning in rats using ...

'Time cells' bridge the gap in memories of event sequences

August 24, 2011
The hippocampus is a brain structure that plays a major role in the process of memory formation. It is not entirely clear how the hippocampus manages to string together events that are part of the same experience but are ...

Fluctuations in size of brain waves contribute to information processing

February 8, 2013
Cyclical variations in the size of brain wave rhythms may participate in the encoding of information by the brain, according to a new study led by Colin Molter of the Neuroinformatics Japan Center, RIKEN Brain Science Institute.

Going places: Rat brain 'GPS' maps routes to rewards

April 17, 2013
While studying rats' ability to navigate familiar territory, Johns Hopkins scientists found that one particular brain structure uses remembered spatial information to imagine routes the rats then follow. Their discovery has ...

Recommended for you

Use of brain-computer interface, virtual avatar could help people with gait disabilities

August 23, 2017
Researchers from the University of Houston have shown for the first time that the use of a brain-computer interface augmented with a virtual walking avatar can control gait, suggesting the protocol may help patients recover ...

Researcher working to develop new tool for non-invasive neuromodulation of human brain

August 23, 2017
A UTA researcher is developing a technology that will map and image the effects of infrared light shone on the human brain that may be able to modulate and improve brain waves and circuits at certain spots in the brain.

Physicist reports binary marker of preclinical and clinical Alzheimer's disease

August 23, 2017
A new technique shows high potential for providing a discrete, non-invasive biomarker of Alzheimer's disease (AD) at the individual level during both preclinical and clinical stages. The proposed biomarker has a large effect ...

Firing of neurons changes the cells that insulate them

August 22, 2017
Through their pattern of firing, neurons influence the behavior of the cells that upon maturation will provide insulation of neuronal axons, according to a new study publishing 22 August in the open access journal PLOS Biology ...

Activating brain region creates intense desire to use cocaine

August 22, 2017
Researchers have identified a portion of the brain that intensifies one's desire for certain rewards—in this case, mimicking addiction to cocaine.

Brain region mediates pleasure of eating

August 22, 2017
Providing the body with food is essential for survival. But even when full, we can still take pleasure in eating. Researchers at the Max Planck Institute of Neurobiology in Martinsried and the Friedrich Miescher Institute ...

2 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

gmurphy
not rated yet Jul 26, 2013
Cool, a basis set of spatial percepts, that's good engineering :)
beleg
not rated yet Jul 27, 2013
Previous experience recall applied to new environments - imagined or encountered.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.