Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Speak, Memory: Research Challenges Theory of Memory Storage

15.11.2006
During sleep, freshly minted memories move from the hippocampus, part of the “old” brain, to the neocortex, or “new” brain, for long-term storage. This has been the reigning theory for decades. Brown University research provides the strongest proof yet of this interaction between the old and new brains – and offers surprising evidence that challenges critical details of this theory of learning and memory. Results appear in Nature Neuroscience.

Daily events are minted into memories in the hippocampus, one of the oldest parts of the brain. For long-term storage, scientists believe that memories move to the neocortex, or “new bark,” the gray matter covering the hippocampus. This transfer process occurs during sleep, especially during deep, dreamless sleep.

Many neuroscientists have embraced and built upon this theory of memory storage, or consolidation, for a generation. But the theory is difficult to test. New research led by Brown University neuroscientist Mayank Mehta, conducted with Nobel Prize-winning physiologist Bert Sakmann, shows the best evidence yet of the sleep dialogue between the old brain and the new.

Their work, published in Nature Neuroscience, also shows that this interaction occurs in a startling way. Instead of the hippocampus uploading information to the neocortex in a burst of brain cell communication, Mehta found the opposite: the neocortex seems to drive the dialogue with the hippocampus.

The findings may give scientists a new understanding of how the brain manages memories in health and during dementia, offering up a fresh look at the causes of diseases such as Alzheimer’s, as well as potential treatments.

“Long-term memory making may be a very different process than we previously thought,” said Mehta, an assistant professor in the Department of Neuroscience at Brown. “Either this reversed dialogue is, somehow, a part of memory storage or this transfer of information from the old to the new brain may not occur during sleep. Either way, the results call into question commonly held theories about the role of cortico-hippocampal dialogue in sleep.”

Edvard Moser, a professor at the Norwegian University of Science and Technology and director of the Centre for the Biology of Memory, is a leading expert on memory processes in the hippocampus. Moser said of the new research, “This technically sophisticated study may significantly influence our view of hippocampal-neocortical interactions during sleep-related memory consolidation processes.”

To study this dialogue, Mehta recorded electrical activity in rat brains. To mimic the deepest sleep states, the rats were anesthetized then fitted with two electrodes. One electrode measured the electrical activity of thousands of cells in the neocortex. These cells were excitatory, meaning that they spark communication between nerve cells. The other electrode recorded the activity of a single inhibitory cell in the hippocampus. These inhibitory cells shut down dialogue between nerve cells.

Using this groundbreaking single-cell recording technique, honed in Sakmann’s laboratory at the Max Planck Institute for Medical Research, researchers made an important finding: During deepest sleep, in both the hippocampus and neocortex, the patterns of neural activity are both regular and highly related. The cells in the old and new brains fired nearly in synch, evidenced by similar peaks and troughs shown on electroencephalographs.

This is surprising; Previous studies showed that during deep sleep, when the excitatory cells in the neocortex showed rhythmic activity, excitatory neurons in the hippocampus showed erratic activity. This stumped Mehta and his colleagues: If these two parts of the brain talk during deep sleep, why didn’t they appear to be speaking the same language? They are, Mehta and his team discovered, if you listen to inhibitory, not excitatory, cells in the hippocampus. Mehta and his team also showed that the activity of the cells is related. The timing of activity, or talk, was the same in both brain regions, with a small delay in the hippocampus – as if those cells were echoing the speech in the neocortex.

This discovery of synchronized communication between the old and the new brain – a phenomenon known as “phase-locking” – has two key implications. It suggests that the neocortex, not the hippocampus, drives the discussion between these brain systems during deep sleep. It also suggests that the inhibitory neurons control the conversation.

Mehta says the findings may change the way neuroscientists look at past experimental data and the way they conduct future research.

“We now have a way, experimentally and theoretically, to see how the two parts of the brain talk to each other,” he said. “This will help us better understand the mechanisms behind learning and memory. But what is really exciting is that this method – simultaneously studying two different cell types in two different brain areas – could be used to study other aspects of brain function, such as perception, emotion, movement. It could open important new avenues for basic and applied research.”

Along with Mehta and Sakmann, Thomas Hahn, a graduate student in the Department of Cell Physiology at the Max Planck Institute for Medical Research, helped conduct the research and also served as lead author of the journal article.

The Max Planck Institute for Medical Research, the National Science Foundation, the National Institutes of Health, NARSAD: The Mental Health Research Association, the Rhode Island Foundation and the Salomon Family Foundation supported the work.

Wendy Lawton | EurekAlert!
Further information:
http://www.brown.edu

Further reports about: Hippocampus Max Planck Institute Mehta Neocortex inhibitory memories neuroscientist

More articles from Life Sciences:

nachricht At last, butterflies get a bigger, better evolutionary tree
16.02.2018 | Florida Museum of Natural History

nachricht New treatment strategies for chronic kidney disease from the animal kingdom
16.02.2018 | Veterinärmedizinische Universität Wien

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

Im Focus: Hybrid optics bring color imaging using ultrathin metalenses into focus

For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.

But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...

Im Focus: Stem cell divisions in the adult brain seen for the first time

Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.

The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...

Im Focus: Interference as a new method for cooling quantum devices

Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters

Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...

Im Focus: Autonomous 3D scanner supports individual manufacturing processes

Let’s say the armrest is broken in your vintage car. As things stand, you would need a lot of luck and persistence to find the right spare part. But in the world of Industrie 4.0 and production with batch sizes of one, you can simply scan the armrest and print it out. This is made possible by the first ever 3D scanner capable of working autonomously and in real time. The autonomous scanning system will be on display at the Hannover Messe Preview on February 6 and at the Hannover Messe proper from April 23 to 27, 2018 (Hall 6, Booth A30).

Part of the charm of vintage cars is that they stopped making them long ago, so it is special when you do see one out on the roads. If something breaks or...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Fingerprints of quantum entanglement

16.02.2018 | Information Technology

'Living bandages': NUST MISIS scientists develop biocompatible anti-burn nanofibers

16.02.2018 | Health and Medicine

Hubble sees Neptune's mysterious shrinking storm

16.02.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>