Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Driving brain rhythm makes mice more sensitive to touch

25.08.2014

By striking up the right rhythm in the right brain region at the right time, Brown University neuroscientists report in Nature Neuroscience that they managed to endow mice with greater touch sensitivity than other mice, making hard-to-perceive vibrations suddenly more vivid to them.

The findings offer the first direct evidence that "gamma" brainwaves in the cortex affect perception and attention. With only correlations and associations as evidence before, neuroscientists have argued for years about whether gamma has an important role or whether it's merely a byproduct — an "exhaust fume" in the words of one — of such brain activity.


Using pulses of blue light in a type of brain cell in the sensory neocortex generated a gamma rhythm that made mice more touch sensitive.

Credit: Micheal Cohea/Brown University

"There's a lot of excitement about the importance of gamma rhythms in behavior, as well as a lot of skepticism," said co-lead author Joshua Siegle, a former graduate student at Brown University and MIT, who is now at the Allen Institute for Neuroscience. "Rather than try to correlate changes in gamma rhythms with changes in behavior, which is what researchers have done in the past, we chose to directly control the cells that produce gamma."

The result was a mouse with whiskers that were about 20 percent more sensitive.

"There were a lot of ways this experiment could have failed but instead to our surprise it was pretty decisive from the very first subject we looked at — that under certain conditions we can make a super-perceiving mouse," said Christopher Moore, associate professor of neuroscience at Brown and senior author of the study. "We're making a mouse do better than a mouse could have done otherwise."

Specifically, Moore and co-first authors Siegle and Dominique Pritchett performed their experiments by using optogenetics — a technique of using light to control the firing patterns of neurons — to generate a gamma rhythm by manipulating inhibitory interneurons in the primary sensory neocortex of mice. That part of the brain controls a mouse's ability to detect faint sensations via its whiskers.

A different part of the brain handles stronger, more imposing sensations, Moore said. The primary sensory neocortex, a particular feature of mammals, has the distinction of allowing an animal to purposely pay attention to more subtle sensations. It's the difference between the feeling of gently brushing a fingertip along a wood board to assess if it needs a bit more sanding and the feeling of dropping the wood board on a foot.

Before anything else in the paper, the researchers confirmed that mice naturally produce a 40-hertz gamma rhythm in their sensory neocortex sometimes. Then they optogenetically generated that gamma rhythm with precise pulses of blue light. Mice with this rhythm could more often detect the fainter vibrations the researchers supplied to their whiskers than could mice who did not have the rhythm going in their brains.

Control and optogenetically stimulated mice alike had been conditioned to indicated their detection of a supplied stimulus by licking a water bottle. The vibrations provided to the mice to sense covered a span of 17 different levels of detectability.

The team's hypothesis was that the gamma rhythm of the stimulated neurons, because they inhibit the transmission of sensation messages by pyramidal neurons in the neocortex with a structured periodicity, actually orders the pyramidal messages into a more coherent and therefore stronger train.

"It's not surprising that these synchronized bursts of activity can benefit signal transmission, in the same way that synchronized clapping in a crowd of people is louder than random clapping," Siegle said.

This idea suggested that the timing of the rhythm matters.

So in another experiment, Siegle, Pritchett, and Moore varied the onset of the gamma rhythm by increments of 5 milliseconds to see whether it made a difference to perception. It did. The mice showed their increased sensitivity only so long as the gamma rhythms were underway 20-25 milliseconds before the subtle sensations were presented. If they weren't, the mice experienced on average no impact on sensitivity.

One of the key implications from the findings for neuroscience, Moore said, is that the way gamma rhythms appear to structure the processing of perception is more important than the mere firing rate of neurons in the sensory neocortex. Mice became better able to feel not because neurons became more active (they didn't), but because they were entrained by a precisely timed rhythm.

Although the study provides causal evidence of a functional importance for gamma rhythms, Moore acknowledged, it still leaves open important questions. The exact mechanism by which gamma rhythms affect sensation processing and attention are not proved, only hypothesized.

And in one experiment, optogenetically stimulated mice appeared less able to detect the most obvious and imposing of the sensations, even as they became more sensitive to the more subtle ones. In other experiments, however, their detection of major sensations was not compromised.

But the possible loss of sensitivity to stimuli that are easier to feel could be consistent with a shifting of attention to fainter ones, said Pritchett, also a former Brown and MIT student now at the Champalimaud Centre for the Unknown in Lisbon, Portugal.

"What we are showing is that, paradoxically, the rhythmic inhibitory input works to amplify threshold stimuli, possibly at the expense of salient stimuli," he said. "This is precisely what you would expect from a mechanism that might be responsible for selective attention in the brain."

Therefore, Siegle, Pritchett, and Moore say they do have a better feel now for what's going on in the brain.

###

The National Institutes of Health funded the research.

David Orenstein | Eurek Alert!
Further information:
http://www.brown.edu

Further reports about: Driving activity clapping evidence feeling neurons processing rhythm rhythms sensitive sensitivity sensory stimuli

More articles from Life Sciences:

nachricht Symbiotic bacteria: from hitchhiker to beetle bodyguard
28.04.2017 | Johannes Gutenberg-Universität Mainz

nachricht Nose2Brain – Better Therapy for Multiple Sclerosis
28.04.2017 | Fraunhofer-Institut für Grenzflächen- und Bioverfahrenstechnik IGB

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Fighting drug resistant tuberculosis – InfectoGnostics meets MYCO-NET² partners in Peru

28.04.2017 | Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

 
Latest News

Wireless power can drive tiny electronic devices in the GI tract

28.04.2017 | Medical Engineering

Ice cave in Transylvania yields window into region's past

28.04.2017 | Earth Sciences

Nose2Brain – Better Therapy for Multiple Sclerosis

28.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>