Memories and sensations: Synchrony is the secret for working together

February 18, 2016, International School of Advanced Studies (SISSA)
Mouse brain recordings. Credit: SISSA

Regions of the brain can "dance" on their own but when they work together they fall in step to a well-timed choreography: according to a study just published in PLOS Biology, when a rat is engaged in a sensory recognition task and needs to make a spatial choice based on previous knowledge, the sensory, motor, and memory regions of the animal's brain (but similar mechanisms are also likely to exist in the human brain), make the rhythms of electrical activity coherent with each other. The study's co-first authors are Natalia Grion and Athena Akrami, research scientists at the International School for Advanced Studies (SISSA) of Trieste, and the study leader is Mathew Diamond, professor of cognitive neuroscience and deputy director of SISSA.

The brain's electrical activity exhibits multiple characteristic "rhythms". One of the most pervasive is theta oscillation, fluctuations of with a typical frequency between 5 and 12 Hz. In rats, for example, it is seen in the hippocampus, a structure engaged in memory processes. By what might seem a strange coincidence, frequencies between 5 and 12 cycles per second are also distinctive of a rat behaviour known as "whisking". Rats explore the world through touch, a sense as useful to them as vision is to us. To palpate surfaces they use their vibrissae, the long hairs on their snout, sweeping them back and forth over objects: whisking is this sweeping movement of their whiskers.

Scientists have asked themselves whether this suspicious coincidence of rhythms in the theta range is by chance or the result of some linkage within the brain. A first series of experiments conducted by an American group a few years ago did not confirm the latter hypothesis, showing instead that when rats explore the environment with their whiskers the rhythms of the different regions were no more synchronized that would be expected of independent oscillators; they did not seem to be linked.

The role of memory

Diamond and his group at SISSA were not convinced that this result conclusively disproved the synchrony hypothesis: perhaps the task used in those experiments was not the best suited to eliciting coherence. "The original task did not require rats to tap their memory and to make a spatial choice, two operations which engage the hippocampus, a region that prominently exhibits the theta rhythm", explains Diamond. "In our experiments we added a component: the rats had to explore an object, identify it, and then make a decision to turn left or right based on the experience gained in previous training sessions".

In this new series of experiments Diamond and co-workers found the connection: the oscillating rhythms of the vibrissae and the theta waves in the hippocampus became phase-locked, for about one second, just before the rat made its choice. In addition, these rhythms were also phase-locked with the activation of the sensory cortex (which collects tactile information), an intermediate processing station between the vibrissae and the hippocampus.

The results were received with enthusiasm by the author of the previous study, David Kleinfeld, of the University of California San Diego, who was commissioned by PLOS Biology to write a commentary (together with Martin Deschênes, of Laval University in Quebec City in Canada, and Nachum Ulanovsky, of the Weizmann Institute of Rehovot in Israel) on Diamond and colleagues' paper.

Explore further: Synchronized brain waves in distant regions combine memories

Related Stories

Synchronized brain waves in distant regions combine memories

January 29, 2016
Humans have the remarkable ability to integrate information from multiple memories and infer indirect relationships. How does our brain support this important function? Neuroscientists from the Donders Institute at Radboud ...

Rats' and bats' brains work differently on the move

April 18, 2013
A new study of brain rhythms in bats and rats challenges a widely used model - based on studies in rodents - of how animals navigate their environment. To get a clearer picture of the processes at work in the mammal brain ...

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, ...

Rats take high-speed multisensory snapshots

May 7, 2013
When animals are on the hunt for food they likely use many senses, and scientists have wondered how the different senses work together. New research from the laboratory of CSHL neuroscientist and Assistant Professor Adam ...

Decoding touch

April 23, 2013
With their whiskers rats can detect the texture of objects in the same way as humans do using their fingertips. A study, in which some scientists of SISSA have taken part, shows that it is possible to understand what specific ...

Past experiences affect recognition, memory, study finds

February 8, 2016
New research from the University of Guelph on the brain and memory could help in developing therapies for peoplewith schizophrenia and Alzheimer's disease.

Recommended for you

Paraplegic rats walk again after therapy, now we know why

March 19, 2018
With the help of robot-assisted rehabilitation and electrochemical spinal cord stimulation, rats with clinically relevant spinal cord injuries regained control of their otherwise paralyzed limbs. But how do brain commands ...

New research into letter-spacing could help improve children's reading

March 19, 2018
Increased letter spacing helps individuals read faster, but not due to visual processing, according to new research from Binghamton University, State University of New York.

Decision-making is shaped by individual differences in the functional brain connectome

March 19, 2018
Each day brings with it a host of decisions to be made, and each person approaches those decisions differently. A new study by University of Illinois researchers found that these individual differences are associated with ...

Scientists locate nerve cells that enable fruit flies to escape danger

March 19, 2018
Columbia University researchers have identified the nerve cells that initiate a fly's escape response: that complex series of movements in which an animal senses, and quickly maneuvers away from, something harmful such as ...

Decoding the chemistry of fear

March 19, 2018
Ask a dozen people about their greatest fears, and you'll likely get a dozen different responses. That, along with the complexity of the human brain, makes fear—and its close cousin, anxiety—difficult to study. For this ...

Kids with severe brain injuries may develop ADHD: study

March 19, 2018
(HealthDay)—Young children who sustain a severe head injury may struggle with attention problems as they grow older, researchers say.


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.