Featured Research

from universities, journals, and other organizations

Neural interaction in silence: Neurophysiologists study widespread networks of neurons responsible for memory

Date:
November 21, 2012
Source:
Max-Planck-Gesellschaft
Summary:
While in deep dreamless sleep, our hippocampus sends messages to our cortex and changes its plasticity, possibly transferring recently acquired knowledge to long-term memory. But how exactly is this done? Scientists have now developed a novel multimodal methodology called “neural event-triggered functional magnetic resonance imaging” and presented the very first results obtained using it in experiments with both anesthetized and awake, behaving monkeys.

Oscillations in the hippocampus: neural interactions during non-REM sleep and periods of silence.
Credit: MPI for Biological Cybernetics

While in deep dreamless sleep, our hippocampus sends messages to our cortex and changes its plasticity, possibly transferring recently acquired knowledge to long-term memory. But how exactly is this done? Scientists from the Max Planck Institute for Biological Cybernetics have now developed a novel multimodal methodology called "neural event-triggered functional magnetic resonance imaging" (NET-fMRI) and presented the very first results obtained using it in experiments with both anesthetized and awake, behaving monkeys.

Related Articles


The new methodology uses multiple-contact electrodes in combination with functional magnetic resonance imaging (fMRI) of the entire brain to map widespread networks of neurons that are activated by local, structure-specific neural events.

Many invasive studies in nonhuman primates and clinical investigations in human patients have demonstrated that the hippocampus, one of the oldest, most primitive brain structures, is largely responsible for the long term retention of information regarding places, specific events, and their contexts, that is, for the retention of so-called declarative memories. Without the hippocampus a person may be able to learn a manual task over a period of days, say, playing a simple instrument, but -- remarkably -- such a skill is acquired in the absence of any memory of having practiced the task before.

The consolidation of declarative memory is thought to occur in two subsequent steps. During the first step, the encoding phase, hippocampus rapidly binds neocortical representations to local memory traces, while during subsequent "off-line" periods of calmness or sleep the new traces are concurrently reactivated in both hippocampus and cortex to strengthen the cortico-cortical connections underlying learned representations. But what is the neural basis of this hippocampal-cortical dialog, and how does hippocampus communicate with the rest of the brain?

For the very first time, Nikos Logothetis, director of the Department for Physiology of Cognitive Processes at the Max Planck Institute for Biological Cybernetics and his team used so-called neural event triggered functional magnetic resonance imaging (NET-fMRI) in both anesthetized and awake, behaving monkeys to characterize the brain areas that consistently increased or decreased their activity in relationship to a certain type of fast hippocampal oscillations known as ripples. Ripples occur primarily during deep sleep and can be measured with electrophysiological methods. Using intracranial recordings of field potentials, the scientists demonstrated that the short periods of aperiodic, recurrent ripples are closely associated with reproducible cortical activations that occur concurrently with extensive activity suppression in other brain structures.

Interestingly, structures were suppressed whose activities could, in principle, interfere with the hippocampal-cortical dialog. The suppression of activity in the thalamus, for instance, reduces signals related to sensory processing, while the suppression of the basal ganglia, the pontine region and the cerebellar cortex may reduce signals related to other memory systems, such as that underlying procedural learning, for example riding a bicycle.

The aforementioned findings offer revealing insights into the large-scale organization of memory, a cognitive capacity emerging from the activation of widespread neural networks which were impossible to study in depth before now using either functional imaging alone or traditional single neuron recordings. Capacities such as perception, attention, learning and memory are actually best investigated using multimodal methodologies such as the NET-fMRI method employed in the MPI study. It is difficult to overstate the importance of the study of the neural mechanisms underlying such capacities, as the vast majority of neurological failures actually reflect dysfunctions of large-scale networks, including cortical and subcortical structures.


Story Source:

The above story is based on materials provided by Max-Planck-Gesellschaft. Note: Materials may be edited for content and length.


Journal Reference:

  1. N. K. Logothetis, O. Eschenko, Y. Murayama, M. Augath, T. Steudel, H. C. Evrard, M. Besserve, A. Oeltermann. Hippocampal–cortical interaction during periods of subcortical silence. Nature, 2012; 491 (7425): 547 DOI: 10.1038/nature11618

Cite This Page:

Max-Planck-Gesellschaft. "Neural interaction in silence: Neurophysiologists study widespread networks of neurons responsible for memory." ScienceDaily. ScienceDaily, 21 November 2012. <www.sciencedaily.com/releases/2012/11/121121145518.htm>.
Max-Planck-Gesellschaft. (2012, November 21). Neural interaction in silence: Neurophysiologists study widespread networks of neurons responsible for memory. ScienceDaily. Retrieved December 20, 2014 from www.sciencedaily.com/releases/2012/11/121121145518.htm
Max-Planck-Gesellschaft. "Neural interaction in silence: Neurophysiologists study widespread networks of neurons responsible for memory." ScienceDaily. www.sciencedaily.com/releases/2012/11/121121145518.htm (accessed December 20, 2014).

Share This


More From ScienceDaily



More Mind & Brain News

Saturday, December 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Researchers Test Colombian Village With High Alzheimer's Rates

Researchers Test Colombian Village With High Alzheimer's Rates

AFP (Dec. 19, 2014) In Yarumal, a village in N. Colombia, Alzheimer's has ravaged a disproportionately large number of families. A genetic "curse" that may pave the way for research on how to treat the disease that claims a new victim every four seconds. Duration: 02:42 Video provided by AFP
Powered by NewsLook.com
Double-Amputee Becomes First To Move Two Prosthetic Arms With His Mind

Double-Amputee Becomes First To Move Two Prosthetic Arms With His Mind

Buzz60 (Dec. 19, 2014) A double-amputee makes history by becoming the first person to wear and operate two prosthetic arms using only his mind. Jen Markham has the story. Video provided by Buzz60
Powered by NewsLook.com
Prenatal Exposure To Pollution Might Increase Autism Risk

Prenatal Exposure To Pollution Might Increase Autism Risk

Newsy (Dec. 18, 2014) Harvard researchers found children whose mothers were exposed to high pollution levels in the third trimester were twice as likely to develop autism. Video provided by Newsy
Powered by NewsLook.com
Yoga Could Be As Beneficial For The Heart As Walking, Biking

Yoga Could Be As Beneficial For The Heart As Walking, Biking

Newsy (Dec. 17, 2014) Yoga can help your weight, blood pressure, cholesterol and heart just as much as biking and walking does, a new study suggests. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Health & Medicine

Mind & Brain

Living & Well

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins