MedicineWorld.Org
Your gateway to the world of medicine
Home
News
Cancer News
About Us
Cancer
Health Professionals
Patients and public
Contact Us
Disclaimer

Medicineworld.org: There is precise communication across brain areas during sleep

Back to neurology news Blogs list Cancer blog  


Subscribe To Neurology News RSS Feed  RSS content feed What is RSS feed?

There is precise communication across brain areas during sleep




-By listening in on the chatter between neurons in various parts of the brain, scientists from the California Institute of Technology (Caltech) have taken steps toward fully understanding just how memories are formed, transferred, and ultimately stored in the brain--and how that process varies throughout the various stages of sleep.

Their findings, reported in the February 26 issue of the journal Neuron, may someday even help researchers understand why dreams are so difficult to remember.



There is precise communication across brain areas during sleep

Researchers have long known that memories are formed in the brain's hippocampus, but are stored elsewhere--most likely in the neocortex, the outer layer of the brain. Transferring memories from one part of the brain to the other requires changing the strength of the connections between neurons and is thought to depend on the precise timing of the firing of brain cells.

"We know that if neuron A in the hippocampus fires consistently right before neuron B in the neocortex, and if there is a connection from A to B, then that connection will be strengthened," explains Casimir Wierzynski, a Caltech graduate student in computation and neural systems, and first author on the Neuron paper. "And so we wanted to understand the timing relationships between neurons in the hippocampus and the prefrontal cortex, which is the front portion of the neocortex".

The research team--led by Athanassios Siapas, a Bren Scholar in the Caltech Division of Biology and an associate professor of computation and neural systems--used high-tech recording and computational techniques to listen in on the firing of neurons in the brains of rats. These techniques helped them pinpoint many neuron pairs that had precisely the kind of synchronous relationship they were looking for--one in which a hippocampal neuron's firing was followed within milliseconds by the firing of a neuron in the prefrontal cortex.

"This is exactly the kind of relationship that would be needed for the hippocampus to effect changes in the neocortex--such as the consolidation, or laying down, of memories," adds Wierzynski.

Once these spike-timing relationships between the hippocampal and prefrontal cortex neurons had been established, the team used their high-tech eavesdropping techniques to hear what goes on in the brains of sleeping rats--since sleep, as Siapas points out, has long been believed to be the optimal time for the memory consolidation.

As it turns out, those thoughts were right--but only part of the time.

The team did indeed hear "bursts" of neuronal chatter during sleep--but only during a phase of sleep known as slow-wave sleep (SWS), the deep, dreamless periods of sleep. "It turns out that during slow-wave sleep there are these episodes where a lot of the cells in the hippocampus will all fire very close to the same time," says Wierzynski. In response, some cells in the prefrontal cortex will fire in near unison as well, just milliseconds later. "What's interesting is that the bulk of the precise spike timing happens during these bursts, and not outside of these bursts," he adds.

Conversely, during rapid-eye-movement (REM) sleep, the previously chatty neuron pairs seemed to talk right past each other, firing at the same rates as before but no longer in concert.

"It was surprising," says Wierzynski, "to find that the timing relationship almost completely went away during REM sleep".

Since REM sleep is the phase during which dreaming occurs, the researchers speculate that this absence of memory-consolidating chatter may eventually help to explain why dreams can be so difficult to remember.

As intriguing as that idea appears to be, the scientists caution that these findings only raise possibilities, providing avenues for further research in the field.

"Now that we've shown this link," says Siapas, "we have a framework we can use to study these questions further. This is just a step toward our goal of some day fully understanding the relationship between memory and sleep".


Posted by: Daniel    Source




Did you know?
-By listening in on the chatter between neurons in various parts of the brain, scientists from the California Institute of Technology (Caltech) have taken steps toward fully understanding just how memories are formed, transferred, and ultimately stored in the brain--and how that process varies throughout the various stages of sleep.

Medicineworld.org: There is precise communication across brain areas during sleep

Acute bacterial meningitis| Alzheimer's disease| Carpal tunnel syndrome| Cerebral aneurysms| Cerebral palsy| Chronic fatigue syndrome| Cluster headache| Dementia| Epilepsy seizure disorders| Febrile seizures| Guillain barre syndrome| Head injury| Hydrocephalus| Neurology| Insomnia| Low backache| Mental retardation| Migraine headaches| Multiple sclerosis| Myasthenia gravis| Neurological manifestations of aids| Parkinsonism parkinson's disease| Personality disorders| Sleep disorders insomnia| Syncope| Trigeminal neuralgia| Vertigo|

Copyright statement
The contents of this web page are protected. Legal action may follow for reproduction of materials without permission.