fmri

A Visit to the fMRI

jhalper — Tue, 29 Apr 2014 04:16:17 +0000

A Visit to the fMRI

I’ve heard that for some the experience of undergoing an MRI scan is claustrophobic, but I find it oddly comfy and cocoon-like. OK, there are those gear-grinding screeches and thumps interrupting the music in the earphones. And the cumbersome set-up for imaging breasts, along with the usual admonition to keep perfectly still, does not leave me in a position I would choose for a nap. Still, I’m on the verge of dropping off when the whole table starts shaking under me. They had warned me about this before I climbed onto the apparatus, but for a second I’m not sure whether to laugh (without moving) or jump off.

The fMRI machine I’m visiting is located in the center of campus. I’m taking part in an experiment on breast imaging for cancer detection. This experiment couldn’t be more timely: One scholarly article after another is calling into question the blanket use of current screening methods, as well as for better methods for early breast cancer detection. Indeed, one of the goals of the experiment was to develop a method that could image the breasts of women of all ages and at various hormonal stages, with a completely safe, non-invasive method, while avoiding some of the frequent false positives that plague the usual types of screening.

Dr. Noam Nissan

PhD research student Noam Nissan, MD, who led this study, talked with me afterwards. Noam is supervised by Prof. Hadassa Degani of the Biological Regulation Department and Prof. Lucio Frydman of the Chemical Physics Department. Those two groups converge on the MRI equipment: Degani developed a highly sensitive, MRI-based method of breast cancer diagnosis called 3TP, which is in clinical use, and more recently she also developed the new, completely non-invasive method based on diffusion measurements; while Frydman is a pioneer in developing novel NMR and MRI techniques.

“I knew I wanted to research cancer, for personal reasons as well as scientific ones,” says Noam. “I had contacted Hadassa almost by mistake, but minutes into our first talk I was introduced to her work in breast cancer research, and I immediately recognized that she would be my supervisor, even though, at the time, I knew almost nothing about the methodology of MRI. ”

Prof. Hadassa Degani

For the experiment, volunteers from three different groups were recruited: Young, premenopausal women; older, postmenopausal women; and lactating women. Detection of cancer in each of these groups, Noam explains, presents a different diagnostic challenge. For the young, premenopausal women, hormonal cycles can get in the way when the current standard MRI method that uses injection of a contrast material is used, thus restricting the scanning to a limited time of the month. Hormone replacement therapy in older women is also problematic for the standard MRI method and it is generally recommended to discontinue it a few months prior the scan, which, again, may lead to delayed diagnosis. There are also problems with using this method in lactating women and pregnant women. In addition, mammography – the standard screening method – is less effective in young women and women treated with hormonal replacement therapy who have unusually dense breast tissue. Although rare, pregnancy-associated breast cancer is not unknown, says Noam and because of the diagnostic challenge with conventional imaging methods, it is often diagnosed late and thus carries a less favorable outcome.

Degani’s new method, Diffusion-Tension Imaging (DTI), does not require any injection of contrast materials, and the experiment showed that it is not sensitive to hormonal changes, so it can potentially be used for all of the above. Part of the method relies on using diffusion gradients in multiple directions, which causes the feeling of shaking in the MRI bed. The other part is computerized analysis of the data. Call it extreme photoshopping: The algorithms they developed begin working immediately after the scanning – while the subject may still be in the fMRI scanner – and provides very fast answers. It consists of analyzing each pixel in the some 60 thin slices of each breast produced in the scan to find any in which the normal, relatively fast diffusion of water is reduced and becomes disordered – a sign of cancer, especially if the neighboring pixels show a similar reduction and disorder. The result is a 3-D, “searchable” image of the breasts that in normal breasts appear in cold colors (purple and blue), while any cancer is highlighted in living color (red and yellow).

The results were published in Radiology, a clinical journal, and the researchers hope that breast DTI will make a relatively quick transition from lab to clinic. According to Noam, DTI can complement the other breast screening methods, giving clinicians a valuable choice in non-standard situations. In the meantime, the lab team is working to apply the method to screening for other forms of cancer, particularly pancreatic cancer, which is often discovered only in the later stages of the disease.

From Radiology Nissan, et al. [0033-8419] 2014

When I asked Noam about the experiment, itself, he told me that I was not alone in my keenness to volunteer. The lab was flooded with calls, including quite a few lactating women. (The experimental setup was not suitable for pregnant women – otherwise they would likely have volunteered as well.) Clearly, he says, there is quite a bit of awareness of the problem as well as willingness to help find a solution.

- Judy Halper

jhalper Tue, 04/29/2014 - 00:16

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Cancer Research

female health

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Very nicely written! Please ping me if you do subsequent blog posts on MRI or fMRI, I'll be glad to tweet, etc. I've been helping some folks at Hebrew Uni with their fMRI expts but I have no idea what's going on at WIS. (Looks like Noam Sobel, my former Berkeley colleague, isn't doing fMRI at the mo.)

Thanks. Noam, indeed, does not use the fMRI much. Neurobiology groups that do are those of Yadin Dudai and Rafi Malach.

Since you were volunteering you had a lot of time to think about the experience, since you were not sick, you were not worried about the results or anything else. Imagine the experience for some one who is there for a test, it is a really is a shaky experience. I have been under the scan myself. I hope the DTI scan will soon be available internationally, because many women under the categories where the standard screening method is not effective could benefit a lot,since some of them actually do have cancer but can not be helped in time because the cancer could not be traced.

absolutely. Thanks

Last Week on ResearchBlogging.org

milhayser — Sun, 02 Mar 2014 10:29:55 +0000

Last Week on ResearchBlogging.org

Solar cells made with bismuth vanadate achieve a surface area of 32 square meters per gram. This compound can be paired with cheap oxides to split water molecules (and make hydrogen) with record efficiency.

Short-term geoengineering could postpone global warming, only to have it happen more quickly in the future.

Carotenoids tinge blackbird bills a deep orange, signalling fitness; birds with oranger bills are "are heavier and larger, have less blood parasites and pair with females in better condition than males with yellow bills."

Fibroblasts can extrude a tidy biological scaffold for stem-cell growth at a nanometer scale, while provoking a lower immune response than synthetic or animal-derived materials.

Higher levels of Omega-3 fatty acids in the blood correlate with stronger white matter in the brain.

By first reverting skin cells to endodermal cells instead of stem cells, researchers were able to transform them into better liver cells with true regenerative potential.

Headband cam reveals that babies spend 25% of their waking lives looking at other people's faces, 96% of which belonged to members of their own race. By the age of 6 months, the faces of another race begin to all look the same.

Here: everything you ever wanted to know about star spiders.

Rodents are similar enough to humans to be used as laboratory models, so does a cat parasite that manipulates the behavior of rats also alter the behavior of humans (30-40% of whom are infected worldwide)?

Researchers have come within 99.8% of the theoretical limit of light absorption enhancement in solar cells, paving the way for "the next generation of high-efficiency, cost-effective and ultra-thin crystalline silicon solar cells."

European utilities, under pressure from a law requiring 20% of all energy to come from renewable sources by 2020, are importing millions of metric tons of wood pellets from the southern United States. Burning these pellets produces less than half the emissions of fossil fuel, not counting the energy needed to ship them across the Atlantic.

Newly discovered chimpanzee populations in the Congo are thriving, outnumbering their cousins in West Africa, but bushmeat hunters, like researchers, are beginning to encroach.

Another study shows a correlation between use of acetaminophen (i.e. Tylenol) during pregnancy and the development of ADHD in children.

New process turns algae into biogas compatible with our natural gas infrastructure. "While it takes nature millions of years to transform biomass into biogas, it takes the SunCHem process less than an hour."

Among single-celled organisms like algae, programmed suicide can benefit relatives while suppressing the growth of non-relatives.

Off-shore wind turbines could significantly slow hurricane winds and decrease storm surges, all while generating electricity.

Novel aerogel made from wood and polymer could be thrown on an oil spill, absorbing nearly 100 times its own weight before being wrung out and used again.

Five-year-olds spanked by their mothers showed increased behavioral problems at age 9. Those spanked by their fathers showed reduced vocabulary.

During a musical "conversation," a jazz musician scanned by fMRI showed activation of language and rhythmic centers in the brain, hemispheric mirrors that "perform syntactic processing for both music and speech." At the same time, there was a marked deactivation of the angular gyrus, which is involved in interpreting the meaning of words if not their syntactic structure.

And finally if you want to be considered a great artist, it might be worth cultivating an eccentric persona in the most sincere manner possible.

For more visit researchblogging.org.

milhayser Sun, 03/02/2014 - 05:29

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Brain and Behavior

Weizmann Science News: Autism, Rain Clouds and a Universal Cancer Therapy

jhalper — Sun, 24 Jul 2011 02:15:53 +0000

Weizmann Science News: Autism, Rain Clouds and a Universal Cancer Therapy

Today's science news from the Weizmann Institute covers research in neurobiology, environmental science and cancer immunology.

â¢ In the first, scientists identified a likely biological marker for autism that shows up even in very young children. Diagnoses of autism are generally not possible so early, as the signs typically appear gradually throughout the first 3-4 years of life. The scientists used fMRI to scan the brains of children aged 1-3 who were just starting to show signs of autistic behavior. Their method: scanning the brains of toddlers while they sleep. It seems that even asleep, brain activity in autistic toddlers is different. In particular, the researchers saw irregularities in synchronization between the left and right hemispheres. The areas tied to language and communication in each half normally exhibit slow fluctuations that are in sync with the other side, but the synchronization was off in around 70% of the autistic toddlers. The more severe their autism, the more pronounced this phenomenon appeared to be. For the near future, the scientists hope this insight can be used to develop early diagnostic tools for the disorder.

As compared to the control brain (top), the autistic brain (bottom) shows weaker inter-hemispheric synchronization in several areas, particularly the superior temporal gyrus (light blue) and the inferior frontal gyrus (red)

â¢ In today's scientific world, ideas and methods flow back and forth between all sorts of seemingly unrelated disciplines. A collaborative effort between a Weizmann Institute scientist and an NOAA researcher suggests that a version of the predator-prey population model (used to describe, for instance, the shared ecology of cheetah and gazelle populations) may accurately describe cycles of cloud formation and rain.

Classic predator-prey model

In the watery version of the model, rain is the predator, clouds are the prey and atmospheric aerosols that seed cloud droplets take the place of the grasslands that provide nutrition to the prey population. Using equations built from the basic principles, the model reveals the sharp transitions between stable and unstable states, as well as the contribution of changes in aerosol levels to shifts in rainfall patterns. Because clouds are still considered big "question marks" in climate change predictions, models like this one can help clarify the bigger picture.

Cloud-rain-aerosol oscillations

â¢ Finally, research by Weizmann Institute immunologists aims to turn a pricey, time-consuming, personalized treatment into an off-the-shelf, universal cancer therapy. In the current therapy, which is now undergoing early-phase clinical trials, a patient's own immune cells are modified outside the body and reinjected. In the new method - which has so far been shown to work in mice - patients would receive injections of immune cells from a ready-made, common donor pool. To prevent rejection of these foreign cells, the patients also receive a mild dose of radiation - just enough to temporarily prevent the immune cells from being given the boot until after they have had a chance to attack the tumor. And, to ensure that these donor immune cells put the short time they have to the best use, they are equipped with receptors for recognizing the cancer cells they are meant to destroy.

jhalper Sat, 07/23/2011 - 22:15

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environmental science

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Casting Memory in Doubt

jhalper — Fri, 01 Jul 2011 05:00:00 +0000

Casting Memory in Doubt

Do you ever doubt your own memory? New research at the Institute suggests that some of the things we think we remember could be wrong. It seems that our brains are surprisingly willing to exchange a true memory for a false one, just on the basis of friends' claims. The scientists not only demonstrated just how easy it is to create false memories, they showed that the switch in memory has a signature pattern of brain activity. The most significant feature? They found strong connectivity between areas of the brain known to be involved in memory and learning, and the amygdala, which, among other things, plays a role in social interaction.

This of course, raises a number of interesting issues and questions. One of the more significant could be this: If memory is so malleable, what is it really for? We may believe our memories to be a personal record of events, but might there be a social aspect to memory that is better served by a tendency to adjust our memories to those of the group?

The amygdala, more often associated with emotions, has been showing up in a number of studies dealing with various aspects of memory conducted by this group and others at the Institute. The implication, here, could be that the rational, information-processing parts of our brain don't really work independently of the emotional, social parts.

jhalper Fri, 07/01/2011 - 01:00

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social interaction and brain

neurobiology

Really interesting. At first glance, you'd assume that accurate-to-reality memories would provide a selective advantage, since past experiences serve as basis for evaluating future scenarios, and an accurate evaluation should provide advantages.

But a single individual's experiences are naturally limited, so an argument could probably be made that a mechanism that allows an individual to assimilate memories from a larger group would also be advantageous - if an individual's experience in an given scenario was somehow atypical, having the memory 'overwritten' with a more typical communal experience might actually lead to forming more accurate expectations, even if, strictly speaking, the memory is wrong.

Quote from Jerome K. Jerome's 1899 book "Idle Thoughts of an Idle Fellow"

"That is just the way with Memory; nothing that she brings to us is complete. She is a willful child; all her toys are broken. I remember tumbling into a huge dust-hole when a very small boy, but I have not the faintest recollection of ever getting out again; and if memory were all we had to trust to, I should be compelled to believe I was there still".

Perhaps the malleability is just an indication of the limitatioins of this amazing biological ability.

Memories are really "stories" and oral history has probably been with us a lot longer than writing. When there's value to society in stories, there's probably also value in editing them.

We assume that our brains work better at comprehending reality than they actually do. It's another collective illusion - we constantly reassure ourselves that we are the pinnacle of evolution, when if we take even a cursory look at human history, we are very limited in our intelligence. We make the same mistakes over and over; we rely on one solution. War, violence, brutality, and tribalism, have only been augmented by technology, not resolved. We know that we are destroying the very environments we depend on, and yet we persist. This is not the sign of an intelligent species.

Is it possible that different types of memories are associated with different levels of malleability. It would seem that the location where a food source ripens at a given time of year would need to remain fairly correct if one is to survive in most habitats where food is not plentiful year around. However, in memories more social than geological/chronological, one might be best served to "go along to get along"...

CaseyR:

Is it possible that different types of memories are associated with different levels of malleability.

This is a really interesting point. Has anyone done experiments on this question?

Memory Booster, Aha Moments and Biological Quantum Phenomena

jhalper — Thu, 31 Mar 2011 03:14:04 +0000

Memory Booster, Aha Moments and Biological Quantum Phenomena

Today's Weizmann Institute news stories include two new papers from the prolific lab of Prof. Yadin Dudai. The first is on a protein that boosts memory in rats. Dudai and his group have been investigating this protein for several years. Previously, they had managed to show that blocking the protein, even for a very short time, erases memories. Now, they have demonstrated that adding more of the protein to certain areas of the brain can strengthen memory. Note: They increased the protein via gene-carrying viruses that infiltrated the rats' brain cells - not a clinic-ready technique. But until we find ways to medically enhance our memories, lead author Reut Shema reminds us that the brain is a dynamic organ - new learning is what causes this protein to be produced in the first place.

The second looks at learning and memory from a different angle altogether: The researchers have found a clue that might explain why things we "get" in a flash of insight tend to stick better in our memories than, say, facts we spend hours memorizing for a test. In a clever experiment, they got volunteers to experience "aha" moments while looking at camouflaged photos interspersed with quick glimpses of the undoctored images. Scans in the fMRI showed that the difference between remembering and forgetting the image behind the camouflage was activity in the amygdala - often called the brain's emotion center. So that satisfying "click" we feel when insight comes out of the blue might just be our amygdala deciding that what we've just figured out is also worth remembering.

(click here to see the solution to the image)

In the last item, quantum mechanics meets molecular biology - areas that, logically, should have nothing in common. Yet, it turns out that a phenomenon that physicists can normally only observe at extremely low temperatures can take place in everyday DNA - at room temperature. That phenomenon is spin selection - a preference for one of the two directions of angular momentum in subatomic particles. A team from the Weizmann Institute and the University of MÃ¼nster in Germany observed the selection of electron spins when they attached DNA to metal electrodes. Apparently, this ability to choose one spin over the other comes from the "spin" of the DNA - the direction in which it twists around to form its double helix. Watch this space for future "spintronic" devices with DNA components.

jhalper Wed, 03/30/2011 - 23:14

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insanlar hafÄ±za sÄ± Ã§ok Ã¶nemlÄ±

It is funny how memory works. I have no expertise in this area, only my views. I can imagine certain drugs having the ability to enhance memory for the general population, and being of specific benefit in cases like dementia.

What I have noted in myself about making memories is that it doesnt necessarily require a aha moment. Yes if I am having a great time, or its something like a first kiss, and adrenalin and many other natural chemicals are involved, yes I will automatically remember an event. But I have also found that to an extent I can make a conscious decision to make a memory. This is not about cramming but deciding and saying (silently) to myself, that this is momentous, this is something I should remember. Its not an automatic prompt, I have trained myself to stop and tell my brain to commit it to memory, because it is important.

So ,,, I wonder how much in the future manufactured drugs will be used in this kind of decision therapy for people to consciously commit something to memory, artificially?

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DWL, couldn't that just be called an aha in slow motion?

You could definitely see your expertise in the work you write. The sector hopes for even more passionate writers like you who aren't afraid to mention how they believe. All the time follow your heart. "We may pass violets looking for roses. We may pass contentment looking for victory." by Bern Williams.

Thanks very much. If you only knew.

A Test of Courage

jhalper — Sun, 18 Jul 2010 23:00:00 +0000

A Test of Courage

Anne Dillard said "You can't test courage cautiously," but Institute scientists have found a way to test it fairly safely, at least.

One might think of courage as an abstract idea, but it turns out that acts of bravery reveal a unique activity pattern in the brain. An experiment at the Institute to identify the brain mechanisms that take control when the call to action conquers fear involved a live snake on a remote-controlled trolley and volunteers with a fear of snakes in an fMRI.

jhalper Sun, 07/18/2010 - 19:00

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I do not know anything about the subject, but if the relevant areas in the brain can be identified, would it not be possible to stimulate them with a weak electric current to help patients overcome -for instance- a socially handicapping phobia?
And once the neurons involved in "courage" get stimulated, will not the neurons progressively get more effective, just like the neurons involved in other often repeated tasks?

Anyone who quotes Annie is OK by me.

That was a well designed experiment. Congratulations.

Neural basis of spatial navigation in the congenitally blind

neurophilosophy — Wed, 30 Jun 2010 13:55:25 +0000

Neural basis of spatial navigation in the congenitally blind

FOR most of us, the ability to navigate our environment is largely dependent on the sense of vision. We use visual information to note the location of landmarks, and to identify and negotiate obstacles. These visual cues also enable us to keep track of our movements, by monitoring how our position changes relative to landmarks and, when possible, our starting point and final destination. All of this information is combined to generate a cognitive map of the surroundings, on which successful navigation of that environment later on depends.

Despite the importance of vision for navigation, congenitally blind people - those born blind - can still generate neural representations of space. Exactly how is unclear, but it is thought to be by using a combination of touch, hearing and smell, and some are even known to use echolocation. Spatial navigation in the congenitally blind is therefore thought to involve different brain networks than those engaged in sighted people. A team of Danish researchers now report, however, that the mechanisms underlying spatial navigation in the blind are much the same as those in sighted people, due to the brain's remarkable ability to reconfigure itself.

The new study, by Ron Kupers and Daniel-Robert Chebat, involved two separate experiments using the same navigation task. In the first, 10 congenitally blind and 10 blindfolded sighted participants spent 4 days learning a route navigation and route recognition task using the BrainPort tongue-display unit (below), a sensory substitution device which translates visual images into touch sensations applied to the tongue.

The principle of sensory substitution was established in the 1960s by Paul Bach-y-Rita, who demonstrated it with a "tactile-vision" device consisting of an old dentist's chair with hundreds of vibrating solenoid stimulators incorporated into the back rest. These acted a bit like pixels, generating a tactile representation of images from a television camera, which was accurate enough to enable blind people to discriminate between objects. This is possible because of the brain's ability to re-route sensory information along novel pathways, one form of the phenomenon referred to as neuroplasticity.

In the navigation task, the participants learned to navigate their way through two virtual routes (above) presented onto their tongues by the device, using the arrow keys on a computer keyboard. At the end of each training day, they were asked to draw each of the virtual routes, to verify that they had generated a cognitive map. In the route recognition task, the participants were automatically guided through the routes by the computer program, and then had to indicate which of the routes had been presented to them by means of the tongue-display unit. Overall, there was no difference in performance between the two groups - both the blind and the sighted participants successfully learned both of the routes, and their drawings became increasingly accurate after each training day.

When, however, they repeated the route recognition task while lying in a brain scanner, important differences in the brain activation patterns were observed. In the blind participants, route recognition produced strong activation of several distinct sub-regions of the visual cortex, and of the right parahippocampus, which is known to contain cells that are involved in spatial navigation. In contrast, the sighted participants exhibited no increase whatsoever in visual cortical or parahippocampal activity. Instead, the task led to activation of various frontal cortical areas. In the second experiment, 10 more sighted participants were trained to perform the same route recognition without blindfolds. They didn't use the tongue display unit either - the virtual routes were presented to them on a computer screen instead. When they repeated it in the brain scanner, the brain activation pattern observed was very similar to that seen in the blind participants in the first experiment.

Although there are numerous studies of how the brain is reorganized following sensory loss, this is one of only a small handful that use functional neuroimaging to investigate the neural basis of spatial navigation in the congenitally blind. One interesting finding is that the hippocampus itself, which is known to contain at least four cell types involved in spatial navigation, was not activated in any of the participants. This may be because it is more important for encoding of cognitive maps, but not their subsequent retrieval. The participants spent 4 days learning the routes, by which time their maps were likely encoded strongly. There is also some evidence that the hippocampus encodes spatial information related to external cues, whereas the parahippocampus encodes it in relation to one's own movements. The frontal cortical activation observed in the sighted participants suggest that they may use a different navigational strategy, one that involves decision-making.

Because of the limited resolution of the tongue display unit, the routes used in the navigation tasks were simplifed versions of computerized mazes that lacked usual environmental features such as landmarks. It is possible, therefore, that the tasks were not demanding enough, but solving them did involve generating cognitive maps, and they were made harder because the sensory information was tactile rather than visual. The study therefore provides evidence that spatial navigation in the absence of vision depends upon the parahippocampus and visual cortex. The findings also suggest that cognitive maps can develop in the complete absence of visual experience, because the visual cortex is capable of processing spatial information received by non-visual senses such as touch.

Related:

Kupers, R. et al. (2010). Neural correlates of virtual route recognition in congenital blindness Proc. Nat. Acad. Sci. DOI: 10.1073/pnas.1006199107.

Bach-y-Rita, P. W. & Kercel, S. (2003) Sensory substitution and the human-machine interface. Trends. Cogn. Sci. 7: 541-546. [PDF]

neurophilosophy Wed, 06/30/2010 - 09:55

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"Exactly how is unclear, but it is thought to be by using a combination of touch, hearing and smell, and some are even known to use echolocation."

All we actually are echolocator. Try to observe how our sounds go and come from the near surfaces. You do function in that way. No matters if you are not aware.

The actual "blindness" from neuroscientists to accept echolocation as universal, may come from centuries trying to divorce themselves from their body, from their senses and sensibility. Neuroscientists seemed "buried" in the Plato cavern called: "isolated brain". But brain is in permanent and open connection within your body, your senses, and the world.

Fortunately, embodied embedded cognition is changing that, towards a sharing transsubjectivity where the observer, the subject, becomes, at different levels, the brain, the body, and the ecosystem.

Symbiodiversity research group and ISMA association have developed several technological tools to enhance all that human "hidden" powers: Copylife code, Infimonikal mathematical system, MimouX co-operating system, and Mokoputomoko server...

Neuron Culture top 5 hits for May

ddobbs — Tue, 01 Jun 2010 09:23:14 +0000

Neuron Culture top 5 hits for May

In reverse order:

5. Â David Sloan Wilson, pissing off the angry atheists.

"I piss off atheists more than any other category, and I am an atheist.ï»¿"Â This sparked some lively action in the comments.

4. Lively or not, Wilson and Dawkins lost fourth place to snail jokes.

A turtle gets mugged by a gang of snails.Â ï»¿

3. A walking tour that lets youÂ See exactly where Phineas Gage lost his mind

2. "Push" science journalism, or how diversity matters more than size

We're constantly told -- we writers are, anyway -- that people won't read long stories. They're hard to sell to editors, probably because editors believe they're hard to sell to readers. I think I read once -- can't recall where, don't know if it's true, we're trusting my hippocampus here, which is a frail thing -- that a major online news magazine found that readership of its stories reliablty fell off as the stories went past the 1000-word mark.

That's probably true. Yet if a long story is written with care, plenty of people read it. The Times'sÂ most-popular-story lists consistently includes long features among their top three entries. (My depression story was there several days.) Clearly length does not always dissuade. Yet the idea that it does dissuade holds strongly enough that writers seldom get the opportunity to write long -- and thus to include the goods that will carry some readers through a science story.ï»¿

1.Â Who you gonna believe, me -- or my lyin' fMRI?

As I noted in anÂ earlier article on the overreach of forensic science, juries tend to be overly credulous about any evidence offered as forensic or scientific evidence. And other studies show that imaging studies generate an extra layer of overcredulousness. (On those, seeÂ Dave Munger andÂ Jonah Lehrer.) So when an 'expert' shows a jury a bunch of brain images and says he's certain the images say a person is lying (or not), the jury will led this evidence far more weight than it deserves.ï»¿

ddobbs Tue, 06/01/2010 - 05:23

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"So when an 'expert' shows a jury a bunch of brain images and says he's certain the images say a person is lying (or not), the jury will led this evidence far more weight than it deserves."

This probably has a lot to do with the fear of asking a stupid question.

Optogenetic fMRI

neurophilosophy — Fri, 21 May 2010 01:50:54 +0000

Optogenetic fMRI

OF all the techniques used by neuroscientists, none has captured the imagination of the general public more than functional magnetic resonance imaging (fMRI). The technique, which is also referred to as functional neuroimaging and, more commonly, "brain scanning", enables us to peer into the human brain non-invasively, to observe its workings and correlate specific thought processes or stimuli to activity in particular regions. fMRI data affect the way in which people perceive scientific results: colourful images of the brain have persuasive power, making the accompanying data seem more credible.

Functional neuroimaging is used widely by researchers, too, with tens of thousands of research papers describing fMRI studies being published in the past decade. Yet, a big question mark has been hanging over the validity of the technique for over a year and, furthermore, the way in which fMRI data are interpreted has also been called into question. Using a novel combination of fMRI and a recently developed state-of-the-art technique called optogenetics, researchers now provide the first direct evidence that the fMRI signal is a valid measure of brain activity.

fMRI measures brain activity indirectly, using signals generated by the flow of blood around the brain. It is based on the assumption that increased blood flow to a particular region of the brain is related to activity in that region, because the cells within it require a supply of oxygen to generate nervous impulses. But several recent studies challenged this assumption. The most important of these, by Yevgeniy Sirotin and Aniruddha Das of Columbia University, showed that the brain pre-empts itself by increasing the flow of blood to regions that might become active in the near future, but that this anticipatory blood flow is not always needed. This prompted the question of whether or not fMRI actually measures what researchers have always claimed it measures.

The new study, published online in the journal Nature, finally answers this question, by confirming that the fMRI signal is indeed closely correlated with increased brain activity. Senior author Karl Deisseroth published one of the first papers describing the optogenetics technique, back in 2005. That paper showed that light-sensitive proteins called channelrhodopsins, which had been isolated from algae several years earlier, can make the neurons sensitive to light when shuttled into them. As a result, light pulses of the appropriate can be used to control the activity of individual, specified cells, on a millisecond timescale. The technique was quickly applied to controlling simple behaviours in small organisms such as nematode worms and fruit flies; more recently, it has been used to successfully control complex functions, such as reward behaviors and memory, in mammals; it has even been used to restore vision in blind mice.

This time, Deisseroth and his colleagues injected a virus carrying the channelrhodopsin gene into the primary motor cortex of mice. The gene was engineered so that it would be expressed specifically in the large pyramidal cells that send axons down into the spinal cord and control movement. The mice were then placed into a custom-made MRI-compatible cradle fitted with a stereotaxic frame to keep their heads still. With the animals inside the scanner, the researchers delivered light pulses to the virus injection site, using an optical fibre inserted through a hole in the skull. In this way, they could activate specified subsets of cells in the motor cortex and simultaneously monitor the fMRI signals generated by them.

The researchers observed fMRI signals (above right) in the motor cortex 3-6 seconds after delivering pulses of light to the motor cortex. The signals originated in the area into which the light pulses were delivered (indicated above by the asterisk) and spread away from it, lasting for about 20 seconds before returning to a baseline level. By contrast, no fMRI response was seen in control mice injected with a salt water solution instead of the ChR2 gene (left). Activity in a part of the brain called the thalamus, which receives connections from the motor cortex, was also observed. This downstream activity was initially weaker than that seen in the cortex, but after a 5-second delay showed a very similar pattern, and reliably followed the cortical activity by several hundredths of a second.

The activity pattern observed in the thalamus again demonstrates that fMRI can accurately measure the activity of groups of neurons. It also shows that the combination of optogenetics and fMRI can be used to investigate how activity in one region of the brain alters activity in distant regions via long-range connections - the 5-second delay is consistent with network activity that modulates the output of the cortex and activity in the thalamus. By introducing ChR2 into the thalamus and performing simultaneous optical stimulation and neuroimaging, the researchers also revealed hitherto unknown details about the pathways connecting the thalamus and motor cortex.

The thalamus is thought of as a 'relay station', which receives sensory information en route to the cortex, and provides the cortex with feedback. The feedback pathways are mostly ipsilateral, that is, they project to the sensory cortical areas on the same side of the brain. The thalamus also sends and receives information to and from the motor cortex, but the former pathways are thought to project to motor areas on both sides of the brain, because control movement involves co-ordination between the two sides of the body. The experiments confirmed this, by showing that optical stimulation of one side of the thalamus evoked activity in the motor cortical areas on both sides.

Previous attempts to investigate the relationship between blood flow and neuronal activity have involved using microelectrodes to stimulate small groups of cells whilst simultaneously performing functional neuroimaging. This method has limitations, because electrical stimulation activates not only those cells targeted by the electrodes, but also distant cells whose axons traverse the stimulated brain region. In these neurons, the electrodes elicit nervous impulses that travel backwards along the axon, causing the cell body to generate further impulses. The resulting activity can therefore potentially confound the fMRI signal, because it is unrelated to that of the targeted cells.

Optogenetic fMRI largely overcomes this problem. Optical stimulation will activate ChR2-expressing axons in the targeted area, and the resultant nervous impulses will be back-propagated. So although some unwanted activity might be observed, it will be related to the cells of interest, because only those cells will be sensitive to light. As well as confirming the validity of fMRI data, this initial description of optogenetic fMRI shows that it is a very powerful technique for investigating neuronal activity at both the local and the global level. The new study does not, however, rule out the possibility that fMRI also detects other unrelated signals. Many questions still remain about exactly how the fMRI signal is generated but, using optogenetics, researchers may soon begin to answer them.

Related:

Lee, J., et al (2010). Global and local fMRI signals driven by neurons defined optogenetically by type and wiring. Nature DOI: 10.1038/nature09108. [PDF]

Boyden, E., et al. (2005). Millisecond-timescale, genetically targeted optical control of neuronal activity. Nat. Neurosci. 8: 1263-1268. [PDF]

McCabe, D. P. & Castel, A. D. (2008). Seeing is believing: The effect of brain images on judgments of scientific reasoning. Cognition: 107: 343-52. [PDF]

neurophilosophy Thu, 05/20/2010 - 21:50

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What disappointed me, however, is that Dr. Bernardine Healy, former Director of the NIH, was a guest and that she didn't slap Maher down hard for his idiotic statements about vaccines and Pasteur.

Ok....I'm just wondering if it is just me or if there is a more widespread thought that subjecting the brain to these kinds of bombardments may have long term effects that have not been sufficiently considered. You know...there are people now who can see the change in energy coloration without the use of machines? Perhaps giving these gifted ones the opportunity to be useful...testing to see if they see what the machine sees...would provide interesting data. Just as those who are on the aspergers to autistic spectrum are able to read the unspoken thoughts of others...and could be used to assist in situations where the patient is unable to speak/communicate....those with other gifts could also be utilized to diagnose and heal.

Do you actually believe that there are people who "can see the change in energy coloration"? And are you really expecting a serious answer?

This is very nice work, and an excellent technique, but no, no, no, no, no it does not show that the fMRI BOLD signal can always be used as a surrogate for neuronal activity (and I appreciate that you are not saying that it can be, but you do say it is âconfirming the validity of fMRI dataâ, it isn't). It is only sometimes that the fMRI BOLD signal corresponds to neuronal activity. That âsometimesâ may be 99% of the time, but it is still only sometimes. Sirotin and Das showed that quite clearly.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2705195/

Pretending that a technique is more reliable than it actually is may falsely inflate the purported value of the research results; it actually decreases their value. Results with fMRI BOLD need to be understood to be not primary measures of neuronal activation. Even when a volume element appears to be highly activated by fMRI (or by any technique), only a small minority of the neurons in that volume element are actually activated simultaneously.

This is a very large issue in my work on basal nitric oxide. The vasodilatation observed in fMRI is produced by NO, by neurogenic NO that causes local vasodilatation. What the BOLD fMRI technique is showing, is where the local NO level is high enough to activate sGC, form cGMP and produce vasodilatation.

Changing the basal NO level changes the amount of neurogenic NO that is needed to raise the local NO level to the threshold that activates sGC and so causes vasodilatation. There is no threshold for changes in basal NO levels to change the volumes activated because differences in NO are already used for regulating the volumes activated.

There are many researchers who don't want to appreciate that the fMRI BOLD technique does not actually measure neuronal activity because it complicates the analysis of their data. I have no sympathy for such researchers. If you are going to use a technique, you need to know and understand the limitations of that technique. It is not being a âpuristâ to demand rigor in how techniques are used and described.

Although the study clarifies previous studies' results on the validity of fMRI by removing the artifacts of electrode stimulation (while creating a cool new method for use in animal work), you're implying that this validates the BOLD signal for all applications of fMRI.

I'd thought that for certain areas fMRI has not been found to have a good correlation with neural firing and that this correlation can switch between tasks. For instance, fMRI is often used to look at the temporal lobe for memory and learning studies. However, fMRI may not be related to actual firing there, but rather to phase-locking to certain brain waves that may correspond better with general dendritic integration rather than actual action potential firing. This phase-locking might vary if the task is a memory encoding task, a memory retrieval task, or a navigation task.

There's also thought that this could be because areas like the motor, visual, and auditory cortices exhibit population coding while the hippocampus and other temporal lobe regions may exhibit sparse coding.

The paper ends with the statement that ofMRI a tool to further probe the controversy - not a solution to the question of whether the BOLD signal is valid.

It's a very interesting study, but I don't see how it validates fMRI as a technique. This study shows: if there's neural activity, then there's an fMRI signal. Most research is based on the assumption: if there's an fMRI signal, then there's neural activity. These are different statements; one may be true and one may be false.

fMRI is valid as a technique to look at vasodilatation.

Vasodilatation is mediated through neurogenic NO. Neuronal activity is mediated through propagation of action potentials.

The coupling between those two things is not one-for-one.

Well..is that true that fMRI signals based on elevated levels of oxygenated blood in specific parts of the brain are caused by an increase in the excitation of specific kinds of brain cells?!?

I view this with baited breath, since so much of the research regarding mental illness will ride on fMRI's in the future.

Gleanings from empathetic ravens, lying brains, dying converence, fading vocabularies, and new books

ddobbs — Tue, 18 May 2010 06:31:00 +0000

Gleanings from empathetic ravens, lying brains, dying converence, fading vocabularies, and new books

RavensÂ via PDPhotoï»¿

Ravens show that consoling one another is also for the birds, Yet another finding that other species have qualities previously thought uniquely human. Our greatest distinction is that we're highly social.Â Yet in that we've got a lot of company. Â ï»¿

Human brains excel at detecting cheaters. FMRI's, not so much, says Vaughan Bell at Mind Hacks-- though in yet another court case, the fMRI lie detection industry pushes another story.

Bell also has a nice write-up of of scintillating RadioLab program on how early dementia shows up in use of language. A stellar program, and short. You'd be demented not to listen to it.

At n+1, Kent Russell offersÂ Eight Playoff Truisms. He's talking hockey, but most of it would go for basketball. I care zero for hockey but found this a fun read.

Backreaction: The Future of the Conference wonders whether we'll quit all this traveling and just conference in cyberspace. I don't see it. No substitute for meatspace, which we manage and mine far more skillfully than anyone does the web. Don't get me wrong, I love the web. But it can't replace meatspace any more than meatscape can it.

You can now orderÂ Here Is a Human Being: At the Dawn of Personal Genomics, byÂ Misha Angrist, a writer who talked his way into being one of the first ten people to have his entire genome sequenced. Haven't read it myself yet, but after meeting Misha and hearing him talk -- and spar with Jim Watson (Angrist is not just a cheerleader for all things genomic) -- I believe this will be a good read.

ddobbs Tue, 05/18/2010 - 02:31

Thanks for including this information and link to "The Future of the Conference". Virtual worlds are an interesting invention, and perhaps the future of the internet itself. I maybe be one of the first however to raise the issue of the implications virtuality has on the mind and brain. Currently, virtual experiences are a fantasy like visual, with some communication potentials, voice or text, Is there a measurable difference to the brain if the virtual world resembles a real life (RL) experience? I believe there mat be, differences in both in the quality of the experience and the memory of it.

I think a theory to pursuit here that could shape the direction of virtual worlds.

I think a theory to pursuit here that could shape the direction of virtual worlds. I agree Ted.Thanks.