Nav: Home

Memory ensembles

February 11, 2016

Memory, i.e. our ability to record, to preserve and to recall our past experiences, makes up one of the most fundamental and fascinating abilities of our brain. For over forty years, neuro-scientists have been interested in the biological mechanisms underlying the storage of the information that our brain records every day. Today, a team from the Faculty of Medicine of the University of Geneva (UNIGE) demonstrates how the brain regulates the size of the neuronal ensembles that reflect the memory trace to optimize performance. By targeting neurons in the hippocampus, the scientists show that it is possible to inhibit - or on the contrary to resurface - a memory. These results can be read in Neuron.

The trace that a memory leaves in our brain is made up of a set of cells located in the hippocampus, called engram. During the encoding of memories, the neurons that form the engram create a network. For a memory to be fixed, the correct number of neurons must be activated. If too many cells are mobilized, the storage of information may become compromised. To understand how memory works, the Geneva researchers investigated the mechanisms that control the recruitment of neurons into the engram. Initiated by Dominique Muller, who tragically passed away last April, this study was conducted by Pablo Mendez and Christian Lüscher from the Department of Basic Neurosciences at UNIGE Faculty of Medicine.

To weaken or strengthen a memory

To study the long-term stability of memory, the scientists presented mice with a particular situation, in order to create a memory. They then exposed these rodents several times to that same situation. By using optogenetics - a technique combining optics and genetics that makes neurons sensitive to light- they stimulated particular neurons. They were thus able to observe that the cells recruited to the engram activate inhibitory cells, which prevent the activation of neighboring neurons. By identifying this inhibition mechanism, the team deciphered how the mobilized neurons control the size of the cell engram and, therefore, the stability of contextual memory.

Pablo Mendez, last author of the study, explains the rest of the experiment: «Since we wanted to know to what extent the size of the cell engram influences memory, we used optogenetics to «force» mice to recruit more or less neurons. Subsequently, we found that the more the engram is significant, the better the memory is preserved, but only up to a limited point. Beyond a certain size, memory no longer works. We were thus able to reinforce a memory, but also to remove it.»

«Now that we know the basic mechanism, we want to decipher how memory itself functions. Which cells for which memories? How do neurons really encode memory? We still have many discoveries to make in order to understand in detail how our brain preserves our memories,» explains Christian Lüscher.
-end-


Université de Genève

Related Neurons Articles:

How do we get so many different types of neurons in our brain?
SMU (Southern Methodist University) researchers have discovered another layer of complexity in gene expression, which could help explain how we're able to have so many billions of neurons in our brain.
These neurons affect how much you do, or don't, want to eat
University of Arizona researchers have identified a network of neurons that coordinate with other brain regions to influence eating behaviors.
Mood neurons mature during adolescence
Researchers have discovered a mysterious group of neurons in the amygdala -- a key center for emotional processing in the brain -- that stay in an immature, prenatal developmental state throughout childhood.
Astrocytes protect neurons from toxic buildup
Neurons off-load toxic by-products to astrocytes, which process and recycle them.
Connecting neurons in the brain
Leuven researchers uncover new mechanisms of brain development that determine when, where and how strongly distinct brain cells interconnect.
More Neurons News and Neurons Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Rethinking Anger
Anger is universal and complex: it can be quiet, festering, justified, vengeful, and destructive. This hour, TED speakers explore the many sides of anger, why we need it, and who's allowed to feel it. Guests include psychologists Ryan Martin and Russell Kolts, writer Soraya Chemaly, former talk radio host Lisa Fritsch, and business professor Dan Moshavi.
Now Playing: Science for the People

#537 Science Journalism, Hold the Hype
Everyone's seen a piece of science getting over-exaggerated in the media. Most people would be quick to blame journalists and big media for getting in wrong. In many cases, you'd be right. But there's other sources of hype in science journalism. and one of them can be found in the humble, and little-known press release. We're talking with Chris Chambers about doing science about science journalism, and where the hype creeps in. Related links: The association between exaggeration in health related science news and academic press releases: retrospective observational study Claims of causality in health news: a randomised trial This...