Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The hunt for mirror neurons – not every technique picks them up

19.02.2013
Researchers in Tübingen have been studying how mirror neurons, which are assumed to be key to the understanding of behaviour, respond when the same action is repeatedly observed.
They found answers in the cerebral cortex of monkeys. The study, published in the journal Nature Communications, has a surprising result: the mirror neuron system does not adapt. This contradicts the original assumption of researchers, that mirror neurons – the same as other nerve cells – react to the frequent repetition of a particular stimulus through a reduced level of activity (adaptation.)

The results of the study highlight the importance of finding a new interpretation of neuroimaging studies that have so far shown that mirror neurons adapt. Astonishingly, these studies had shown adaptation. Researchers at the Hertie Institute for Clinical Brain Research (HIH) and the Werner Reichardt Centre for Integrative Neuroscience at the University of Tübingen have found an explanation for these apparently contradictory results.

Mirror Neurons Respond to Goal-Directed Behaviours
As with other nerve cells, it is possible to stimulate mirror neurons, which can transmit this stimulation on to other nerve cells. This happens with the help of electrical impulses, which ‘fire’ up to several hundred times a second. This ‘firing’ can be measured by an electrode. Researchers had previously discovered that mirror neurons control hand movements that are directed towards a particular goal, for instance grasping a piece of apple. Yet what is special about mirror neurons is that they are similarly active when these kinds of goal-directed actions are merely observed. Hence they might play a decisive role in comprehending the behaviour of other people.

Unexpected Pattern of Activity Baffles researchers
‘Surprisingly, it was shown that two thirds of mirror neurons did not adapt their firing patterns, as had previously been assumed’, says Pomper, a scientist at the Hertie Institute for Clinical Brain Research (HIH). Studies carried out with functional Magnetic Resonance Imaging (fMRI) had shown the opposite: the mirror neurons adapted, that is they reacted more and more weakly to the repetition of the same stimulus.
Not Every Approach is Able to Measure
The activity measured by fMRI is only able to record the ‘firing’ of nerve cells indirectly. It merely identifies changes in the blood flow through oxygen levels in the red blood cells. Experts describe this as the BOLD effect. They are evoked by the energy needs of active nerve cells. Input signals, certain processing stages in the cell protruberances (dendrites) and cell bodies, along with the activity of glial cells, another element of the nervous system, also contribute to this. ‘‘As a result, conclusions about the behavior of individual cells cannot be drawn directly from changing in BOLD signal’ says Dr. Vittorio Caggiano, formerly at Hertie Institute for Clinical Brain Research and Center for Integrative Neuroscience, University Clinic Tübingen(1).The assumption up to now has always been that an adaptation of nerve cells was the basis of the reduction of the BOLD effect seen in experiments when the same action is subsequently performed and then observed. According to the authors of the study, on the basis of the results of the current study the former interpretation of the BOLD adaptation does not stand up.

So how to explain the BOLD adaptation? One interpretation the researchers can offer is the additional raised local field potentials (LFP) in the brain: these do in fact manifest the anticipated adaptation and so they could explain the fMRI data. In every nerve cell the signal transfer goes through input signals and occasionally output signals, so-called action potentials. If the input signal to be converted into an output signal, that would lead to the firing of neurotransmitters. These in turn stimulate the next nerve cell along as a transfer signal. The researchers suggest that LFP express the input signals that come from other areas of the brain and the expression of them in a particular region.

New Interpretation of the Current Study
It has always been that mirror neurons fire in the same way regardless of whether a subject personally performs an action or watches it. Therefore they seemed to be verifiable when one compares the fMRI signals from the execution and the observation of actions, whether of the same kind or different. ‘A one-to-one correspondence of fMRI data and the activity of mirror neurons is thus not possible. Hence from our point of view the need to find a new account of the neuro-imaging studies based on adaptation’ is ho it is summarized by Peter Their, a member of the HIH board and Chairman of the CIN.

(1) Present address: McGovern Institute for Brain Research, Massachusetts Institute of Technology (MIT)

Publication
Mirror neurons in monkey area F5 do not adapt to the observation of repeated actions; Vittorio Caggiano, Joern K. Pomper, Falk Fleischer, Leonardo Fogassi, Martin Giese & Peter Thier; Nature Communications 4, Article number: 1433 doi:10.1038/ncomms2419; Received 31 May 2012, Accepted 20 December 2012, Published 05 February 2013; http://www.nature.com/ncomms/journal/v4/n2/full/ncomms2419.html

Press contact
Silke Jakobi

Head of Communication
HIH Hertie Institut for Clinical Brain Research
Center of Neurology Tübingen
Otfried-Müller-Str. 27
72076 Tübingen
Phone ++ 49 (0)7071/29-88800
Fax ++ 49 (0)7071/29-4796
silke.jakobi(at)medizin.uni-tuebingen.de

Silke Jakobi | idw
Further information:
http://www.uni-tuebingen.de
http://www.nature.com/ncomms/journal/v4/n2/full/ncomms2419.html

More articles from Medical Engineering:

nachricht 'Memtransistor' brings world closer to brain-like computing
22.02.2018 | Northwestern University

nachricht MRI technique differentiates benign breast lesions from malignancies
20.02.2018 | Radiological Society of North America

All articles from Medical Engineering >>>

The most recent press releases about innovation >>>

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

Im Focus: Developing reliable quantum computers

International research team makes important step on the path to solving certification problems

Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...

Im Focus: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

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...

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

Stiffness matters

22.02.2018 | Life Sciences

Magnetic field traces gas and dust swirling around supermassive black hole

22.02.2018 | Physics and Astronomy

First evidence of surprising ocean warming around Galápagos corals

22.02.2018 | Earth Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>