Now see this: Anti-inflammatory treatment reverses stroke-induced compromise in sensory learning
Localization, size, and demarcation of the photothrombotic (PT) lesion in the mouse cortex. (A) Top view of a mouse brain with a PT-lesion in the left hemisphere (red dotted circle). (Scale bar, 1 mm.) (B) Scheme illustrating average lesion location and size: lesion center was located in the left primary somatosensory cortex (S1), on average 1.3 mm anterior to (the anterior border of) the primary visual cortex (V1) and 1.8 mm lateral to the midline. We overlaid the scheme with an optically recorded retinotopic map from the binocular part of V1 to directly illustrate the spatial relationship of the PT-lesion and V1. (C) Nissl-stained frontal section through a lesion center 7 d after lesion induction. The left brain hemisphere is illustrated showing that the lesion was restricted to the cortex without affecting the underlying white matter or subcortical regions. (Scale bar, 500 μm.) (D) The higher magnification image of the lesion border (region demarcated by the black rectangle in C shows the intact tissue and cortical layering in the perilesional zone. (Scale bar, 500 μm.) Copyright (c) PNAS, doi: 10.1073/pnas.101645810
(Medical Xpress) -- One of the many potential consequences of ischemic stroke a lesion, or localized pathological change in the brain, in which blood flow insufficient to meet metabolic demand leads to poor oxygen supply (cerebral hypoxia) is compromise to two different visual plasticity paradigms: sensory learning (the enhancement of visual acuity and contrast sensitivity of the open eye after monocular deprivation, or MD, in which vision in one eye is blocked) and ocular dominance, or OD, plasticity (a shift in the ocular dominance of neurons in the binocular part of the visual cortex toward the open eye after MD). A standard view holds that changes in the activity of the major thalamocortical afferents to the visual cortex (the afferents from the left and right eye) are sufficient to induce OD-plasticity.
Recently, however, research conducted at the Bernstein Fokus Neurotechnologie (BFNT) and Johann-Friedrich-Blumenbach Institut für Zoologie und Anthropologie at Universität Göttingen in Germany has shown that after a photothrombotically-induced stroke outside the visual system (a lesion induced in the mouse somatosensory cortex by intravenous injection of photosensitive dyes that, when irradiated, cause photochemical occlusion of the irradiated vessels with secondary tissue ischemia), there was neither an enhancement of visual acuity nor an OD-shift after MD but OD-plasticity was present in the hemisphere contralateral to the lesion.
In addition, anti-inflammatory treatment restored sensory learning but not OD-plasticity the same results obtained by implementing a two-week delay between photothrombosis and MD. The researchers were thus able to conclude that both sensory learning and OD-plasticity are compromised in the areas surrounding a cortical lesion, and that transient inflammation is responsible for impaired sensory learning suggesting that anti-inflammatory treatment may be useful adjuvant therapy in post-stroke rehabilitation. Moreover, in a finding significant to researchers modeling the visual system, the study clearly demonstrates that nonlocal influences i.e., factors outside of the visual cortex or visual system can modify the sensitivity of the visual cortex to changes in afferent activity patterns and are thus more important in OD-plasticity than has previously been thought.
Conducted by Franziska Greifzu, a graduate student in Prof. Siegrid Löwels Systems Neuroscience Group, along with Silvio Schmidt, Karl-Friedrich Schmidt, Otto W. Witte, and Klaus Kreikemeier, the primary challenges facing the research team were selecting the lesion model that best addressed their questions, as well as controlling reproducible lesion size and location.
To solve those challenges, says Löwel, we didnt need to develop totally new techniques, but used well-establish ways of answering a question that is very often addressed using only in vitro techniques. The strength of our approach was to combine behavioral analyses and in vivo imaging of brain activities in the same animals.
The results were surprising given previous in vitro knowledge: One of the best-known model systems in neuroscience to study brain plasticity is visual cortex OD-plasticity, initially introduced in the 1960s by the subsequent Nobel Prize winners David Hubel and Torsten Wiesel1. It was firmly believed, Löwel explains, that one can induce ocular dominance plasticity in the visual cortex by depriving one eye of an animal i.e., monocular deprivation. As a result, the MD-affected animals visual cortex will be activated more strongly by visual stimulation of the non-deprived eye while deprived eye afferents get weakened. Our data clearly show that this plasticity does not just depend on changes in the major thalamocortical afferents from the eyes to the visual cortex, but in fact must be modulated by non-local influences.
Despite the strength of the results, Löwel is cautious in speculating on how their findings may impact the development of post-stroke treatment and prophylaxis. First of all, so far we have only analyzed mice and have to be very careful not to create more hope in patients than is justifiable. Nevertheless, she continues, the observation that anti-inflammatory treatment had a therapeutic effect on the investigated learning paradigm might be the starting point for further investigations.
Turning to future research, Löwel notes that the team plans to analyze the cellular mechanisms underlying these plasticity changes using in vivo two-photon microscopy, which will allow then to visualize individual nerve cells and their changes after stroke. In terms of in silico computer modeling, however, she states that If you want to analyze learning after brain lesions, one has to investigate real brains. There is no way around this conclusion. We do not yet know enough about brain mechanisms to switch to in silico protocols. She does point out that We of course use computational neuroscience techniques for analyzing data properly and for creating hypothesis about brain mechanisms.
Other avenues for future research, adds Löwel, is the role of GABAergic neurons in post-lesion OD-plasticity, as well as having already started to investigate changes in inhibitory networks and interhemispheric interactions.
Of great promise, Löwel concludes, is applying their techniques to investigate other forms of neural plasticity. I think the combination of behavioral analyses with imaging of neuronal activity in the same animals perhaps even chronically to follow the same individual over time in a learning experiment is very powerful. One can even perform so-called chronic two-photon calcium imaging experiments to follow single neurons over time. It is therefore possible to follow the activity of larger nerve cell ensembles or even single nerve cells in the brains of individuals during a learning experiment.
More information: Global impairment and therapeutic restoration of visual plasticity mechanisms after a localized cortical stroke, PNAS published online before print August 24, 2011, doi: 10.1073/pnas.1016458108
1Related: An introduction to the work of David Hubel and Torsten Wiesel, Eric R. Kandel, doi: 10.1113/jphysiol.2009.170688, June 15, 2009, The Journal of Physiology, 587, 2733-2741
Copyright 2011 PhysOrg.com.
All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com.
- Study suggests caution on a new anti-obesity drug in children May 07, 2008 | not rated yet | 0
- Adult brain can change, study confirms Sep 05, 2007 | not rated yet | 0
- Disinhibition plus instruction improve brain plasticity Apr 12, 2011 | not rated yet | 0
- New period of brain 'plasticity' created with transplanted embryonic cells Mar 25, 2010 | not rated yet | 0
- Revealing the machinery underlying the 'plastic' juvenile brain Feb 28, 2007 | not rated yet | 0
- Motion perception revisited: High Phi effect challenges established motion perception assumptions Apr 23, 2013 | 3 / 5 (2) | 2
- Anything you can do I can do better: Neuromolecular foundations of the superiority illusion (Update) Apr 02, 2013 | 4.5 / 5 (11) | 5
- The visual system as economist: Neural resource allocation in visual adaptation Mar 30, 2013 | 5 / 5 (2) | 9
- Separate lives: Neuronal and organismal lifespans decoupled Mar 27, 2013 | 4.9 / 5 (8) | 0
- Sizing things up: The evolutionary neurobiology of scale invariance Feb 28, 2013 | 4.8 / 5 (10) | 14
question on coriolis effect with drag force
1 hour ago I really need help with this question. A small floating object initially moves with velocity v on the surface of a liquid at latitude λ. The...
Question of reflection and transmission of TEM wave in normal incidenc
7 hours ago Suppose TEM wave in +z normal to a boundary on xy plane at z=0. We know *E* & *H* are tangential to the boundary. Let ##\vec E_i=\hat x E##, be the...
the rudyak-krasnolutski effective potencial
8 hours ago Hi ... anyone now how to calculate or the formula of the rudyak-krasnolutski EFFECTIVE potencial ? the effective potencial includes the angular...
Normal force for a lever model
9 hours ago My model is a lever on a table top. One arm is horizontal on the table, while the other arm is raised at an angle alpha. I'm assuming the weight of...
gravity is std. therefore can we rate a 'mass at height' by watts?
15 hours ago For example.... wind turbines are primarily listed by their wattage (1.5MW etc.) Presumably their output is varied according to rotational speed, so...
Calculating on-axis elements of a solenoid
May 22, 2013 I wanted to mention that this solenoid has many winds over many layers. The thickness of the windings is 2.4 inches coming off of the engineering...
- More from Physics Forums - Classical Physics
More news stories
Little is known about why asthma develops, how it constricts the airway or why response to treatments varies between patients. Now, a team of researchers at Weill Cornell Medical College, Columbia University Medical Center ...
Inflammatory disorders 10 hours ago | not rated yet | 0 |
The negative effects of poorly controlled asthma symptoms on sleep quality and academic performance in urban schoolchildren has been confirmed in a new study.
Inflammatory disorders May 21, 2013 | not rated yet | 0
Patients with inflammatory bowel disease (IBD) are at higher risk of melanoma, a form of skin cancer, report researchers at Mayo Clinic. Researchers found that IBD is associated with a 37 percent greater risk for the disease. ...
Inflammatory disorders May 20, 2013 | 4.5 / 5 (2) | 0
(Medical Xpress)—Inflammation is an important response in the body - it helps you to kill off invaders such bacteria that could cause a harmful infection. But if it's chronic or uncontrolled, inflammation can also cause ...
Inflammatory disorders May 14, 2013 | 5 / 5 (1) | 0 |
New research by medical students working in the Breathe Well Centre of Research Excellence at the UTAS School of Medicine has revealed swimming has health benefits for young people with asthma, with no adverse effects on ...
Inflammatory disorders May 10, 2013 | 5 / 5 (1) | 0
High blood glucose is associated with poor outcomes in hospitalized patients, and use of intensive insulin therapy (IIT) to control hyperglycemia is a common practice in hospitals. But the recent evidence does not show a ...
17 minutes ago | not rated yet | 0
(Medical Xpress)—Regulating the distribution of power in neurons is done by a system that makes the national electric grid look simple by comparison. Each neuron has several thousand mitochondria confined ...
6 hours ago | 4.8 / 5 (5) | 0 |
A brief visual task can predict IQ, according to a new study. This surprisingly simple exercise measures the brain's unconscious ability to filter out visual movement. The study shows that individuals whose ...
12 hours ago | 4.4 / 5 (9) | 0 |
Teams of highly respected Alzheimer's researchers failed to replicate what appeared to be breakthrough results for the treatment of this brain disease when they were published last year in the journal Science.
10 hours ago | 5 / 5 (1) | 2 |
Scientists at the National Institutes of Health report they have discovered in mouse studies that a small molecule released in the spinal cord triggers a process that is later experienced in the brain as ...
10 hours ago | 5 / 5 (2) | 0 |
(HealthDay)—Type 2 diabetes is more aggressive in children than adults, with signs of serious complications seen just a few years after diagnosis, new research finds.
3 hours ago | not rated yet | 0