Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Functional Magnetic Resonance Imaging under the Magnifying Glass

08.11.2012
Tübinger scientists reveal laminar differences in neurovascular coupling between positive and negative BOLD responses.

The cortex consists of six different layers, which vary in their anatomical and physiological properties. It plays a key role in the cognitive capacities of the brain. Since the cortical layers are segregated functionally, we could potentially say something about the neural processes that take place when an area is activated if we could see different signals in the different layers.


A: The stimulus used to elicit positive and negative BOLD responses in the visual cortex;
B: Positive and negative BOLD responses in monkey primary visual cortex to a visual stimulus;
C: The cerebral blood volume (CBV) response to a visual stimulus is increased in the entire primary visual cortex.

Jozien Goense / Max Planck Institute for Biologische Cybernetics, Tübingen

Jozien Goense from the Max Planck Institute for Biological Cybernetics in Tübingen, Germany and her colleagues used functional Magnetic Resonance Imaging (fMRI) to observe these layer-specific neural processes within the cortex and found different mechanisms for fMRI response increases and decreases as well as cortical layer-dependent differences in the neurovascular coupling mechanism.

The cortex is the outermost layer of the brain and plays a key role in perception, memory, attention, thought, language and consciousness. In mammals, it consists of six horizontal layers, each with different anatomical and physiological properties and different connectivity. These layers have so far been elusive to study in vivo, for several reasons, like a lack of spatial resolution in functional Magnetic Resonance Imaging (fMRI), the inability to see deeper layers with various optical methods, or difficulty in determining the exact recording depth of electrodes. Therefore, if we can visualize the signals in the different layers, it would allow us to better probe the cortical circuitry, for example to determine the processing steps that occur between the input and output of a given cortical area.

Functional Magnetic Resonance Imaging (fMRI) is one of the most used tools to observe the functional activity of the brain. fMRI is a non-invasive method that measures brain activity by detecting associated changes in blood flow and oxygen consumption. The primary form of fMRI uses the blood-oxygenation-level-dependent (BOLD) contrast, which reflects the oxygen concentration in the blood, and through this indicates which brain areas are activated upon a certain stimulus. However, typical fMRI studies measure activation on the scale of a few millimeters and are not able to resolve the cortical layers. Furthermore, it is also not yet known if and how layer-specific neural activity is reflected in the BOLD-response. Other functional imaging methods that are less commonly used, but can shed light on this question, are based on the cerebral blood volume (CBV), whereby the amount of blood in the activated brain region is measured, or based on cerebral blood flow (CBF). These various methods have different sensitivities and measure different aspects of the blood flow response upon neural activity.

Jozien Goense is a project leader in the Department for Physiology of Cognitive Processes headed by Nikos Logothetis at the Max Planck Institute for Biological Cybernetics in Tübingen, Germany. She and her colleague Hellmut Merkle from the Laboratory of Functional and Molecular Imaging at the National Institutes of Health in Bethesda (USA), used high-resolution fMRI to measure BOLD-, CBV- and CBF responses to stimuli that elicit positive- and negative BOLD signals in the macaque primary visual cortex. They compared the activity patterns in response to excitatory stimuli, and stimuli that are known to give negative BOLD responses. Negative BOLD responses are reductions in the BOLD signal, often seen adjacent to stimulated regions. The negative BOLD signal is therefore thought to result from neuronal suppression.

They found that a negative BOLD response is not just the inverse of the positive response, but that it has a separate mechanism. Furthermore, the different layers responded differently to the stimuli. This indicates that the neurovascular coupling mechanism, which is the mechanism that provides the link between the neural signals and the BOLD-response, differs in the different layers and for the two stimuli. This means that potentially the layer-specific differences in the responses can be used to separate what kind of processes occur in the cortex.

These findings suggest different mechanisms for neurovascular coupling for BOLD increases and decreases as well as laminar differences in neurovascular coupling. The consequences of these findings are quite fundamental, since it may improve the interpretation of the BOLD signals in fMRI studies, and especially the negative one. Furthermore, it opens up the possibility to study neural processes within the cortical sheet, which would expand the applicability of fMRI and push it to smaller spatial scales than the ones it is currently used at.

Original Publication:
J. Goense, H. Merkle, N. K. Logothetis. (2012) High-resolution fMRI reveals laminar differences in neurovascular coupling between positive and negative BOLD responses. Neuron, doi: 10.1016/j.neuron.2012.09.019
Contact:
Dr. Jozien Goense
Phone: +49 7071 601-1704
E-mail: jozien.goense@tuebingen.mpg.de
Stephanie Bertenbreiter (Public Relations)
Phone: +49 7071 601-1792
E-mail: presse-kyb@tuebingen.mpg.de
The Max Planck Institute for Biological Cybernetics works in the elucidation of cognitive processes. It employs about 300 people from more than 40 countries and is located at the Max Planck Campus in Tübingen, Germany. The Max Planck Institute for Biological Cybernetics is one of 80 research institutes that the Max Planck Society for the Advancement of Science maintains in Germany and abroad.

Stephanie Bertenbreiter | Max-Planck-Institut
Further information:
http://www.kyb.tuebingen.mpg.de/
http://www.tuebingen.mpg.de/

More articles from Life Sciences:

nachricht A Map of the Cell’s Power Station
18.08.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau

nachricht On the way to developing a new active ingredient against chronic infections
18.08.2017 | Deutsches Zentrum für Infektionsforschung

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>