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How to be a neuroscientist

In this post, I will teach you all how to be proper, skeptical neuroscientists. By the end of this post, not only will you be able to spot "neuro nonsense" statements, but you'll also be able to spot nonsense neuroscience questions.

I implore my journalist friends to take note of what I say in this post.

Much has already been said on the topic of modern neuroimaging masquerading as "new phrenology". A lot of these arguments and conversations are hidden from the lay public, however, so I'm going to expose the dirty neuroscientific underbelly here.

Bradley Voytek Cognitive Neuroscience New Phrenology fMRI

(Image source: The Roots - Phrenology)

This post was prompted by a question over on Quora: What is the neurological basis of curiosity? Where does curiosity reside in the brain?

The question itself is of a type that is commonly asked in cognitive neuroscience: where is <vague behavior> in the brain?

But what does it even mean to ask where "curiosity" is in the brain? What would an answer look like?

According to the article linked to in the current top answer on Quora:

In study after study, scientists have found that the striatum lit up like an inferno of activity when people didn’t know exactly what was going to happen next, when they were on the verge of solving their mystery and hoped to be rewarded—it was more active then, in fact, than when people received their reward and had their curiosity satisfied.

"So," you may ask, "what's wrong with that answer? That seems reasonable and sound and very sciencey!"

You just got brain-mesmerized!

I can prove, with one statement, that this answer is wrong (if you're impatient, jump to point 2 at the bottom).

I'm not picking on the person who answered the question; they had no way to know. They were just following the discourse of the media narrative about neuroscience findings.

So what is wrong with this explanation (he says, finally getting to the damned point)? I'll break both of these points down in detail later.

1. The question is phrased in such a way that it presumes that "curiosity" is a singular thing.

2. The question presumes that a complex behavior or emotion can be localized to a brain region or regions. There are several philosophical pitfalls packaged into the answer, such as the ontological commitment to the narrative of cognitive neuroscience and the cerebral localization of function.

To be clear, what I'm not saying is that behaviors aren't in the brain. What I am saying is that the cerebral localization narrative is too simplistic.

Let me break down these points.

1. "Is curiosity a singular thing?"
When you ask "where is curiosity in the brain" you assume that researchers can somehow isolate curiosity from other emotions and behaviors in a lab and dissect it apart. This is very, very difficult, if not impossible. Neuroimaging (almost always) relies on the notion of cognitive subtraction, which is a way of comparing your behavior or emotion of interest (curiosity) against some baseline state that is not curiosity.

Or, as I say in my book chapter from The Mind and the Frontal Lobes:

The underlying assumption in these studies is that activity in brain networks alters in a task-dependent manner that becomes evident after averaging many event-related responses and comparing those against a baseline condition. Deviations from this baseline reflect a change in the neuronal processing demands required to perform the task of interest.

2. "Can curiosity be localized to one brain region?"
Bradley Voytek PNAS basal ganglia prefrontal cortex striatum

No, it cannot. Here's how I know: I've personally worked with people who have a severely damaged striatum. Know what? They still have curiosity. If the striatum is where curiosity is in the brain, how can someone whose striata are gone still have curiosity? They cannot. Yet they do. Poof. Hypothesis disproved.

Imagine asking "where is video located in my computer?" That doesn't make any sense. Your monitor is required to see the video. Your graphics card is required to render the video. The software is required to generate the code for the video. But the "video" isn't located anywhere in the computer.


Now there's a subtlety here. It may be that people with damaged striata have curiosity impairments (whatever that means), which would agree with the fMRI study discussed in that link above, but it proves that the striatum is not where curiosity is in the brain. More technically: the striatum may be a critical part of a network of brain regions that support curiosity behaviors, but that is different from saying that the striatum is where curiosity is.

Or, as I say in my chapter:

...the cognitive subtraction method... provide[s] details of functional localization that can then be tested and corroborated using other methodologies, including lesion studies. The interpretation of these localization results is confounded, however, by a lack of clarity in what is meant for a "function" to be localized. For example, Young and colleagues (2000) noted that for a given function to be localizable that function "must be capable of being considered both structurally and functionally discrete"; a property that the brain is incapable of assuming due to the intricate, large-scale neuronal interconnectivity.

Thus, discussing behavioral functions outside of the context of the larger cortical and subcortical networks involved with that function is a poorly posed problem. Therefore, the scientific study of cognition requires detailed neuroanatomical and connectivity information to compliment functional activity findings.

God. I was going to end this with some links to news stories talking about neuroscientists finding out where (love/happiness/hate/prejudice/sexytimes/etc.) were located in the brain, but I just gave up. There are some damned many of them.

If you're a journalist and you're reading this, please change the way you talk about these results.

If you're a student, if you remember nothing else from this post, just remember to ask, "can a person who has a lesion to that brain region not experience that emotion or do that behavior anymore?" If the person still can, then that is not where that behavior is located in the brain. And, in all likelihood, that function can't be localized to any one region at all.

Editor's selection: Neuroscience
This post was chosen as an Editor's Selection for ResearchBlogging.org
Editor's selection: Social Science
This post was chosen as an Editor's Selection for ResearchBlogging.org
Barres, B. (2010). Neuro Nonsense PLoS Biology, 8 (12) DOI: 10.1371/journal.pbio.1001005
Racine E, Bar-Ilan O, & Illes J (2005). fMRI in the public eye. Nature Reviews Neuroscience, 6 (2), 159-64 PMID: 15685221
Editors (2004). Brain scam? Nature Neuroscience, 7 (7), 683-683 DOI: 10.1038/nn0704-683
Weisberg, D., Keil, F., Goodstein, J., Rawson, E., & Gray, J. (2008). The Seductive Allure of Neuroscience Explanations Journal of Cognitive Neuroscience, 20 (3), 470-477 DOI: 10.1162/jocn.2008.20040
Young, M., Hilgetag, C., & Scannell, J. (2000). On imputing function to structure from the behavioural effects of brain lesions Philosophical Transactions of the Royal Society B: Biological Sciences, 355 (1393), 147-161 DOI: 10.1098/rstb.2000.0555

brainSCANr: Paper rejected and Health2.0!

(This is cross-posted from the brainSCANr blog)

Sorry for the silence these last few weeks! With Jess back in school and Brad back from break, we've had to refocus on our "real world" work again.

To give a brief few updates, the brainSCANr manuscript was not even sent out for review (hooray!) so we decided to do a few presubmission inquiries at journals to see if it's even of interest to anyone. We're sure the paper will find a home, we're just not sure where.

Also, we've set up a Google Group for discussion. You can join it here:

Bradley Voytek Jessica Voytek brainSCANr careMAPr Health2.0

This past Saturday, Brad and Jess spent all day at the Health2.0 Developer Challenge (aka the "code-a-thon") at the Googleplex. This event was intended to pair researchers, developers, designers, and folks from the health industry to provide rapid prototypes to address social and person issues in health and medicine.

Neither of us really knew what to expect when we got there, but it ended up being a really cool experience. We started with Brad giving a brief presentation to the crowd about brainSCANr and why we built it. This piqued the interest of a few people in the crowd, and soon we were off in a group discussing some other possibilities with data-mining PubMed.

After about an hour, we were met by Alex from MEDgle (another great heath data mining service), who recognized Brad from Twitter.

We quickly decided on a tool to map where the primary research on health topics was being performed, and one of the members of the group (Sean) dubbed this "careMAPr".

You can see the rapid demo prototype here:

Bradley Voytek Jessica Voytek brainSCANr careMAPr Health2.0

Right now this only works for ADHD for the USA, but the idea would be to allow anyone to enter any search term, and we would query PubMed for that topic. From the results we can identify where the primary research is being conducted. The user could even search by year to highlight only researchers who have recently published on a topic, for example.

The problem that we are trying to address with this site is how to connect the lay community with research specialists. The use case scenario we presented was this: imagine you are a parent whose child was recently diagnosed with ADHD. Maybe your kid was prescribed a drug as part of their treatment. But maybe your child also has another disease, and you want to know about research looking at the relationship between that disease and ADHD.

Right now, the best most people have is to do some Google searching (which can result in very dubious or even misleading information). You can talk to a psychiatrist, but maybe that doctor doesn't really know much about ADHD. How can you find a clinician in your area who does? We hoped that our site might serve as such a resource.

Anyway, the project was very fun, and we were all pretty surprised with how much we managed to put together in just a few hours. We're not sure if we're going to see this one through the the finish, but we hope to.

What do people think about the idea? Any suggestions?


Something ghoti with science citations

Science has a lot of problems. Or rather, scientometrics has a lot of problems. Scientific careers are built off the publish or perish foundation of citation counts. Journals are ranked by impact factors. There are serious problems with this system, and many ideas have been offered on how to change it, but so far little has actually been affected. Many journals, including the PLoS and Frontiers series, are making efforts to bring about change, but they are mostly taking a social tactic: ranking and commenting on articles.

I believe these methods are treating the symptom, not the problem.

Bradley Voytek drunk ghoti

Publish or perish reigns because our work needs to be cited for we scientists to gain recognition. Impact factors are based on these citation counts. Professorships are given and tenure awarded to this who publish in high-ranking journals. However citations are biased, and critical citations are often simply ignored.

Bear with me here for a minute. How do you spell "fish"? g-h-o-t-i: "g-h" sounds like "f", as in "laugh". "o" sounds like "i", as in "women". "t-i" sounds like "sh", as in "scientific citations". This little linguistic quirk is often (incorrectly) attributed to George Bernard Shaw; it's used to highlight the strange and inconsistent pronunciations found in English. English spelling is selective. You can find many spelling examples that look strange, but support your spelling argument.

Just like scientific citations.

Bradley Voytek scientometrics

There are a lot of strange things in the peer-reviewed scientific literature. Currently, PubMed contains more than 18 million peer-reviewed articles with approximately 40,000-50,000 more added monthly. Navigating this literature is a crazy mess. When we created brainSCANr, our goal was to simplify complex neuroscience data. But now we want to shoot for more.

At best, as scientists we have to be highly selective about what studies we cite in our papers because many journals limit our bibliographies to 30-50 references. At worst, we're very biased and selectively myopic. On the flip side, across these 18+ million PubMed articles, a scientist can probably find at least one peer-reviewed manuscript that supports any given statement no matter how ridiculous. Don't believe me? Here's my first whack at a questionable series of statements supported by peer-reviewed literature:

Human vision extends into the ultraviolet frequency range1, possibly mediated by an endogenous violet receptor2.


The effects of retroactive prayer are well-described in improving patient outcomes1. Herein we examine the hypothesis that such retroactive healing is mediated by an innate human ability for "psi"; that is, for distance healing mediated by well known quantum effects2.

What we need is a way to quickly assess the strength of support of a statement, not an authors' biased account of the literature. By changing the way we cite support for our statements within our manuscripts, we can begin to address problems with impact factors, publish or perish, and other scientometric downfalls.

brainSCANr is but a first step in what we hope will be a larger project to address what we believe is the core issue with scientific publishing: manuscript citation methods.

We argue that, by extending the methods we present in brainSCANr to find relationships between topics, we can adopt an entirely new citation method. Rather than citing only a few articles to support any given statement made in a manuscript, we can create a link to the entire corpus of scientific research that supports that statement. Instead of a superscript number indicating a specific citation within a manuscript, any statement requiring support would be associated with a superscript number that represents the strength of support that statement has based upon the entire literature.

For example, "working memory processes are supported by the prefrontal cortex"0.00674, gets strong support, and a link to PubMed showing those articles that support that statement. Another statement, "prefrontal cortex supports breathing"0.00033, also gets a link, but notice how much smaller that number is? It has far less scientific support. (The method for extracting these numbers uses a simple co-occurrence algorithm outlined in the brainSCANr paper).

My citation method removes citation biases. It provides the reader a quick indication of how well-supported an argument is. If I'm reading this paper and I see a large number, I might not bother to look it up as the scientific consensus is relatively strong. But if I see an author make a statement with a low number--that is, a weak scientific consensus--then I might want to be a bit more skeptical about what follows.

We live in a world where the entirety of scientific knowledge is easily available to us. Why aren't we leveraging these data in our effort to uncover truth? Why are we limiting ourselves to a method of citations that has not substantially changed since the invention of the book? My method may have flaws, but it much harder to game than the current citation biases that only give us the narrowest slice of scientific support. My citation method entirely shifts the endeavor of science from numbers and rankings of journals and authors (a weak system for science, to say the least!) to a system wherein research is about making statements about truth. Which is what science should be.


. (2006). The Impact Factor Game PLoS Medicine, 3 (6) DOI: 10.1371/journal.pmed.0030291
(2010). How to improve the use of metrics Nature, 465 (7300), 870-872 DOI: 10.1038/465870a
Robinson KA, & Goodman SN (2011). A systematic examination of the citation of prior research in reports of randomized, controlled trials. Annals of Internal Medicine, 154 (1), 50-5 PMID: 21200038


Top 10 neuroscience TED talks

Neuroscience and neuroscientists seem to be a popular staple of TED. As a neuroscientist, this makes TED basically brain-porn for me. There have been so many excellent TED talks on the topic, and I wanted to collect my favorites here (with some commentary). Mind you, this list isn't complete, it's just representative of my neuroscientific tastes.

I've listened to or watched hundreds of TED talks. But I know it's popular right now to give some TED hate. The most common criticism I've seen is that TED is a way for the rich to pat themselves on the back.

But you know what? I've genuinely learned a lot from watching the TED talks. Who cares if it costs folks $6k a pop to attend, when so many talks are posted online for free? In a society where 30 seconds of advertising during the Super Bowl costs $2.6M and American Idol draws 20 million weekly viewers, I'll definitely take some rich folks paying money to gather and talk to each other about interesting topics.

In 2010, I had the honor of giving a talk at TEDxBerkeley about my neuroscience research and my experience growing up watching my grandfather deteriorate from Parkinson's disease. In preparing for that talk, I got a lot of speaking inspiration from some of these talks. Here are my favorites.

Oliver Sacks

There's not a lot I can say about Sacks that hasn't yet been said. His books were a huge inspiration for my career, my research, and my way of thinking about the brain. The profiles he gives of his patients are fascinating insights into how the brain works, and very thoughtful and caring. Seriously, if you haven't yet, go read The Man Who Mistook His Wife for a Hat and An Anthropologist on Mars.

He also just seems like an interesting guy. He did a lot of drugs back in med school, has recently survived cancer (as profiled beautifully by Steve Silberman), and is a regular on RadioLab, my favorite podcast.

In this talk he profiles several patients who have experienced hallucinations caused by damage to the eyes, such as from macular degeneration. This phenomenon is called Charles Bonnet syndrome, and Sacks talks about it in his usual amazing manner.

Jill Bolte Taylor

My first introduction to Jill Bolte Taylor was through her book, My Stroke of Insight. I was given her book by Prof. Marian Diamond, who has become quite well known for her YouTube videos on anatomy. At the time, I was the graduate lab instructor for Marian Diamond's neuroanatomy course. Dr. Diamond knew I working with patients who had stroke, and she gave me Dr. Jill Bolte Taylor's book in the hopes that I gained some empathic insight into what the experience of a stroke was like. She was right. It was amazing.

Now, while I don't agree with all of Jill Bolte Taylor's interpretations of the neuroscience in her talk (e.g., "the right hemisphere 'thinks' in pictures; "the left hemisphere functions like a 'serial processor'"), it's quite amazing never the less.

Henry Markram

Okay, okay, so I've given Henry Markram and the Blue Brain Project some shit on this blog before. Hell, I'm quoted in the New York Times as a bit of a naysayer for this kind of stuff (although my full quote was, "...every neuroscientist will agree that the endeavor is important and worthwhile. It's a necessary tool in the neuroscientific repertoire. The backlash is against the hype.")

But Henry Markram gives a great talk about why brain simulation is important for neuroscience, and he gives one version of how we can go about it. My favorite quote from this talk is toward the beginning when he says, "we can't keep doing animal research forever". While I believe there are also potential future issues with brain simulation, there's a great quote from Bill Crum in his correspondence to Nature:

To my mind, there is a moral inconsistency attached to studies of higher brain function in non-human primates: namely, the stronger the evidence that non-human primates provide excellent experimental models of human cognition, the stronger the moral case against using them for invasive medical experiments. From this perspective, 'replacement' should be embraced as a future goal.

Vilayanur Ramachandran

Ahhhh VS Ramachandran. He's such a great speaker. Sure, he's on record for equating mirror neurons to the discovery of DNA (sigh...), but like Sacks he has some great insight into the damaged brain and, more importantly, what that means about what it means to be human. The Capgras delusion is so fascinating, and I love his explanation of it. Hell, we use it for our fake-science explanation of why zombies don't attack one another!

Anyway he does go on to talk about his classic (and amazing) phantom limb research. Check out his book, Phantoms in the Brain. (Man, I should be getting kick-backs from Amazon for all these friggin' book links.)

Sebastian Seung

I AM MY CONNECTOME! ::chuckles:: Okay, that awkwardness aside, I love his work, and Seung really manages to explain, in clear language, why this work is so important.

Granted, I'm also biased about this one, too...


Bradley Voytek brainSCANr

Gero Miesenboeck

Man did Miesenboeck get overshadowed by Karl Deisseroth or what? Nature named optogenetics the Method of the Year in 2010 not because of Miesenboeck, but because Deisseroth had 10 (TEN) Nature* publications in 2010 alone (and he had 4 in Science, too).

Anyway, Miesenboeck's talk explains optogenetics and its applications beautifully. Such a great talk. It also contains one of my favorite TED talk quotes: "So it seems the only trait that survives decapitation is vanity".

And mark my words: the Nobel Prize in Physiology or Medicine in 2020 will be awarded for the optogenetics work of Lima, Miesenboeck, and Deisseroth.

Michael Merzenich

I've got a huge amount of love for Merzenich's research. He's done groundbreaking work showing how important neuroplasticity is for cognition, behavior, and learning. In this talk he manages, in 20 some minutes, to give a very thorough overview of this great work. Again, this is another researcher who greatly influenced my thinking and indirectly lead me down the path to my Neuron paper.

Jeff Hawkins

My views on this talk are similar to how I feel about a lot of the neuroscience TED talks: I don't necessarily agree with all of their arguments or scientific points, but Hawkins offers some cool theories and he's working hard on them in an interesting way. He's got a couple of phrases he uses that I don't like (e.g., "old/alligator brain"), but hey, it's a lay lecture. I'll cut some slack.

I wrote a bit about Hawkins, his book On Intelligence, and Numenta before on Quora. Rather than write it all again from scratch, here's the full thing:

When I first started my PhD, Hawkins was still running the Redwood Neuroscience Institute, which at the time was affiliated with UC Berkeley (since the founding of Numenta, it has now been fully absorbed into Berkeley as the Redwood Center for Theoretical Neuroscience). The RNI was founded on the ideas presented in On Intelligence. The energy of the whole endeavor was amazing, and it was hard not to believe in him.

The main idea in the book is that there are nested hierarchies of cortical modules that give rise to a predictive functionality, and that this is a critical, core functionality of the human brain. There's been some cool research out of Berkeley (e.g., Badre et al., 2009) showing that there is a hierarchical organization within the frontal cortex related to cognition. The idea isn't an old one, but Hawkins organizes it and gives it a good foundation.

It's an excellent start (clearly the brain does make predictions), but it's well-known from psychology that another thing we humans are good at is adding a post hoc narrative explanation to something that we did unconsciously, or that has no obvious explanation. Obviously this kind of phenomenon indicates a "broken" prediction mechanism where we make a "prediction" of something after it has already happened, and then we tend to remember the event as though we accurately predicted it beforehand!

So basically, yeah. Brains is hard. Hawkins is smart and he's onto something, but it's not the whole story. But I'm sure he'll get something out of it in terms of working classification and prediction algorithms, even if those algorithms don't have anything to do with what the brain turns out to be actually doing.

Christopher deCharms

So when I first saw this back in 2008, I was thinking, "ugh, so much hype". Well, here we are only about 3 years later and I've seen more of what Christopher deCharms and his company Omneuron have been up to, and I gotta say I'm a bit more impressed now. It's fMRI-based (and if you know me, you know my feeling about fMRI), so there's that. But the potential for real-time fMRI paired with biofeedback for patient treatment is enormous, so I'm gonna hold my breath and hope they pull this off.

Dan Gilbert

Okay, okay, so it's not strictly neuroscience per se, but damn if Dan Gilbert's talk on how context shapes our behavior and psychology isn't great. Just watch it.

Daphne Bavelier

This is such a great talk providing good, real evidence to counter a lot of nonsense, reactionary claims about the negative effects of video games on our brains. Check out my full write-up about this talk here.


Gabrielle Giffords' brain surgery: Decompressive hemicraniectomy

So the big news this weekend was the terrible shooting in my home state of Arizona. The highest-profile victim was congresswoman Gabrielle Giffords who, as of this writing, is recovering from surgery after being shot in the head.

Most early reports of her shooting listed her as dead. My belief is that this is because people hear "shot in the head" and immediately translate that into "dead". Many surgeons would, as well.

However, according to the BBC, Giffords' surgeon, Peter Rhee, was "a former military doctor who served in Afghanistan" and her neurosurgeon, Michael Lemole, "removed half of her skull to give the [brain] tissue room. The bone is being preserved at a cold temperature and can be reattached when the swelling subsides."

The article does not, however, explain this procedure very well, and so I thought I'd give a little bit of an explanation.

This surgery is known as a decompressive hemicraniectomy. I've published research with people who have had this procedure, blogged about that work, talked about it a TEDxBerkeley last year, and even got picked up by Mind Hacks and Wired for it. Here's what the skull of a person who has had this surgery looks like:

Bradley Voytek Journal of Cognitive Neuroscience Giffords Hemicraniectomy

And in 3D:

This surgery is amazing. As I said in the last piece, I worked with a surgeon at San Francisco General Hospital, Geoff Manley.

Dr. Manley has recently published several papers on the clinical benefits of performing a decompressive hemicraniectomy on people who have had some kind of head trauma. To give a little bit of a background, a decompressive hemicraniectomy is a surgical procedure in which the surgeon actually removes a large part of the skull (see the picture at the right) after someone has had head trauma that has caused the pressure inside the skull to increase. This can happen in a few ways, but basically, because the head is an enclosed system, if the brain swells arteries can get pressed closed. This can cut off the blood supply to different brain areas. The swelling can also cause the brain to press down onto the brainstem which can lead to coma or death.

There is a scale that is used to describe someone's neurological state after a head injury. This is known as the Glasgow Coma Scale (GCS), which is a numerical scale ranging from 3 to 15, which 3 being nearly dead. A person who shows up with a GSC of 3 can even be viewed as a lost cause, with very little chance of survival. Points are assigned based upon observations of the eyes, movement, and verbalization by the patient. A 3 would mean the patient does not open their eyes to any stimulation, has no movements, even in response to pain, and makes no sounds.

One of the patients we worked with in my study had a GSC of 6 in the field, which dropped to a 3 by the time he got to the hospital. That subject

...underwent an emergency decompressive hemicraniectomy and removal of the subdural hematoma because of his rapid neurological deterioration. At the time of EEG testing, he was doing remarkably well and had no evidence of any residual neurological or behavioral deficits.

Another patient:

Subject 1 sustained a gunshot wound to the left frontal lobe anterior to premotor and motor cortices. His Glasgow coma scale (GCS) was 14 on admission. The patient was taken to the operating room for debridement of the gunshot wound, and a decompressive hemicraniectomy was performed to prevent further neurological deterioration from increasing ICP [intracranial pressure] from the initial penetrating brain injury. At the time of EEG testing, his memory, attention, and motor function were normal and he did not have any frontal release signs. Of note, the patient is currently back to school.

Now, of course I'm not a medical doctor, have no details about Congresswoman Giffords' medical state, or anything like that. But hearing that her neurosurgeon performed a decompressive hemicraniectomy gives me hope that she may well recover from this attack.

Anyway, I hope this serves as a way of some explanation of what her surgery was, and why it was performed.

EDIT: I've written an even simpler explanation of this over at Quora:

Basically, the gunshot caused tissue damage of the actual brain tissue. This leads to swelling. Of course, the head is an enclosed space, so the brain tissues can only swell up onto the skull causing compression and threatening to cut off blood supply or down, through the opening at the base of the skull (foramen magnum) causing a herniation (in this case, and "uncal herniation"). This swelling down onto the brainstem stem compresses the tissues there, damaging the neurons. The brainstem neuronal structures are responsible for basic functions required for life such as respiration and maintenance of consciousness. Damaging these tissues leads to rapid degeneration of status, coma, and then death.

EDIT #2: Looks like CNN's Dr. Gupta agrees with me.


Voytek B, Secundo L, Bidet-Caulet A, Scabini D, Stiver SI, Gean AD, Manley GT, & Knight RT (2010). Hemicraniectomy: a new model for human electrophysiology with high spatio-temporal resolution. Journal of Cognitive Neuroscience, 22 (11), 2491-502 PMID: 19925193