Neurons in the brain tune into different frequencies for different spatial memory tasks

April 17, 2014
Researchers recorded gamma waves in the brains of rats navigating through a simple environment to understand how current and past locations are represented in the brain. Credit: Laura Colgin/University of Texas at Austin

Your brain transmits information about your current location and memories of past locations over the same neural pathways using different frequencies of a rhythmic electrical activity called gamma waves, report neuroscientists at The University of Texas at Austin.

The research, published in the journal Neuron on April 17, may provide insight into the cognitive and disruptions seen in diseases such as schizophrenia and Alzheimer's, in which are disturbed.

Previous research has shown that the same brain region is activated whether we're storing memories of a new place or recalling past places we've been.

"Many of us leave our cars in a parking garage on a daily basis. Every morning, we create a memory of where we parked our car, which we retrieve in the evening when we pick it up," said Laura Colgin, assistant professor of neuroscience and member of the Center for Learning and Memory in The University of Texas at Austin's College of Natural Sciences. "How then do our brains distinguish between current location and the memory of a location? Our new findings suggest a mechanism for distinguishing these different representations."

Memory involving location is stored in an area of the brain called the . The neurons in the hippocampus that store spatial memories (such as the location where you parked your car) are called place cells. The same set of place cells are activated both when a new memory of a location is stored and, later, when the memory of that location is recalled or retrieved.

When the hippocampus forms a new spatial memory, it receives sensory information about your current location from a brain region called the . When the hippocampus recalls a past location, it retrieves the stored spatial memory from a subregion of the hippocampus called CA3.

The entorhinal cortex and CA3 transmit these different types of information using different frequencies of gamma waves. The entorhinal cortex uses fast gamma waves, which have a frequency of about 80 Hz (about the same frequency as a bass E note played on a piano). In contrast, CA3 sends its signals on slow gamma waves, which have a frequency of about 40 Hz.

Colgin and her colleagues hypothesized that fast gamma waves promote encoding of recent experiences, while slow gamma waves support memory retrieval.

They tested these hypotheses by recording gamma waves in the hippocampus, together with electrical signals from place cells, in rats navigating through a simple environment. They found that place cells represented the rat's current location when cells were active on fast gamma waves. When cells were active on slow gamma waves, represented locations in the direction that the rat was heading.

"These findings suggest that fast gamma waves promote current memory encoding, such as the memory of where we just parked," said Colgin. "However, when we need to remember where we are going, like when finding our parked car later in the day, the hippocampus tunes into slow gamma waves."

Because gamma waves are seen in many areas of the brain besides the hippocampus, Colgin's findings may generalize beyond . The ability for neurons to tune into different frequencies of gamma waves provides a way for the brain to traffic different types of information across the same neuronal circuits.

Colgin said one of the next steps in her team's research will be to apply technologies that induce different types of gamma waves in rats performing memory tasks. She imagines that they will be able to improve new memory encoding by inducing fast gamma waves. Conversely, she expects that inducing slow gamma waves will be detrimental to the encoding of new memories. Those slow gamma waves should trigger old memories, which would interfere with new learning.

Explore further: Why your nose can be a pathfinder

Related Stories

Why your nose can be a pathfinder

April 16, 2014
Waves in your brain make smells stick to your memories and inner maps.

Brain's motor cortex uses multiple frequency bands to coordinate movement

February 21, 2014
Synchrony is critical for the proper functioning of the brain. Synchronous firing of neurons within regions of the brain and synchrony between brain waves in different regions facilitate information processing, yet researchers ...

Brain waves encode information as time signals

December 16, 2013
How information is processed and encoded in the brain is a central question in neuroscience, as it is essential for high cognitive function such as learning and memory. Theta-gamma oscillations are "brain waves" observed ...

Brain activity may mark the beginning of memories

April 14, 2014
By tracking brain activity when an animal stops to look around its environment, neuroscientists at the Johns Hopkins University believe they can mark the birth of a memory.

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.

Study finds analysis of many species required to better understand the brain

April 29, 2013
To get a clear picture of how humans and other mammals form memories and find their way through their surroundings, neuroscientists must pay more attention to a broad range of animals rather than focus on a single model species, ...

Recommended for you

Researchers find monkey brain structure that decides if viewed objects are new or unidentified

August 18, 2017
A team of researchers working at the University of Tokyo School of Medicine has found what they believe is the part of the monkey brain that decides if something that is being viewed is recognizable. In their paper published ...

Artificial neural networks decode brain activity during performed and imagined movements

August 18, 2017
Artificial intelligence has far outpaced human intelligence in certain tasks. Several groups from the Freiburg excellence cluster BrainLinks-BrainTools led by neuroscientist private lecturer Dr. Tonio Ball are showing how ...

Study of nervous system cells can help to understand degenerative diseases

August 18, 2017
The results of a new study show that many of the genes expressed by microglia differ between humans and mice, which are frequently used as animal models in research on Alzheimer's disease and other neurodegenerative disorders.

How whip-like cell appendages promote bodily fluid flow

August 18, 2017
Researchers at Nagoya University have identified a molecule that enables cell appendages called cilia to beat in a coordinated way to drive the flow of fluid around the brain; this prevents the accumulation of this fluid, ...

Researchers make surprising discovery about how neurons talk to each other

August 17, 2017
Researchers at the University of Pittsburgh have uncovered the mechanism by which neurons keep up with the demands of repeatedly sending signals to other neurons. The new findings, made in fruit flies and mice, challenge ...

Neurons involved in learning, memory preservation less stable, more flexible than once thought

August 17, 2017
The human brain has a region of cells responsible for linking sensory cues to actions and behaviors and cataloging the link as a memory. Cells that form these links have been deemed highly stable and fixed.

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

russell_russell
not rated yet Apr 18, 2014
An interesting thesis.
Have humans go through the paces, mazes and tests too.
Have humans park their cars in any parking scenario you choose.

1.)Make sure anywhere they park their car all other cars present are indistinguishable from their own car as far as the area they are able see - the horizons of their field of vision is concerned.

2.)Make sure anywhere they park their car all other cars present are distinct from their own car as far as the area they are able see - the horizons of their field of vision is concerned. (As an example here: their car is white, any and/or all other cars are black)

.3)Continue to choose any parking scenario (parameters of choice) that gives or takes away support to the hypothesis proposed.

Return humans test subjects back to their natural habitat after all testing is done.

If any, what are the signal differences of frequency between the success or failure of participants ability to recall, reconstruct, reenact, retrieve or remember location?

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.