Modeling of Large-Scale Functional Brain Networks Based on Structural Connectivity from DTI: Comparison with EEG Derived Phase Coupling Networks and Evaluation of Alternative Methods along the Modeling Path

New findings from Holger Finger, Marlene Bönstrup, Bastian Cheng, Arnaud Messé, Claus Hilgetag, Götz Thomalla, Christian Gerloff, Peter König

doi: http://dx.doi.org/10.1101/043109

This article is a preprint and has not been peer-reviewed [what does this mean?].

Abstract

Here we use computational modeling of fast neural dynamics to explore the relationship between structural and functional coupling in a population of healthy subjects. We use DTI data to estimate structural connectivity and subsequently model phase couplings from band-limited oscillatory signals derived from multichannel EEG data. Our results show that about 23.4% of the variance in empirical networks of resting-state fast oscillations is explained by the underlying white matter architecture. By simulating functional connectivity using a simple reference model, the match between simulated and empirical functional connectivity further increases to 45.4%. In a second step, we use our modeling framework to explore several technical alternatives along the modeling path. First, we find that an augmentation of homotopic connections in the structural connectivity matrix improves the link to functional connectivity while a correction for fiber distance slightly decreases the performance of the model. Second, a more complex computational model based on Kuramoto oscillators leads to a slight improvement of the model fit. Third, we show that the comparison of modeled and empirical functional connectivity at source level is much more specific for the underlying structural connectivity. However, different source reconstruction algorithms gave comparable results. Of note, as the fourth finding, the model fit was much better if zero-phase lag components were preserved in the empirical functional connectome, indicating a considerable amount of functionally relevant synchrony taking place with near zero or zero-phase lag. The combination of the best performing alternatives at each stage in the pipeline results in a model that explains 54.4% of the variance in the empirical EEG functional connectivity. Our study shows that large-scale brain circuits of fast neural network synchrony strongly rely upon the structural connectome and simple computational models of neural activity can explain missing links in the structure-function relationship.

YES. My DTI MRI is scheduled for next week

And here I thought they’d forgotten about me…

But this afternoon, I got a call from the MRI place to schedule my DTI MRI. They can see me next Wednesday afternoon, which is pretty awesome.

DTI MRI shows white matter connections in the brain — all the “cables” that communicate between the different sections, showing how everything is “talking to each other”.

Tomorrow, I have my EEG and autonomic function testing first thing in the morning. I’m not sure what I was thinking, scheduling it for 9:30 a.m. on a workday, when I have to deal with metro area traffic.

But there it is. I’ve got my appointments for tomorrow. And I’m looking forward to actually getting some data about my situation, instead of personal accounts and impressions. I need measurements. If you can’t measure it, you can’t manage it.

And after that, I have my neuropsych appointment at noon. There are only four more sessions with them, and it seems strange that after eight years, they’re going away.

But this happens all the time. And after being all torn up over it last weekend, I’m dealing.

Just get on with it.

So, that’s the news. I’m really excited to be getting all this done. It’s going to cost me some more money, but that’s what my flexible spending account is for at work. To offset this cost. So, it will.

Onward.

Treating TBI

Treating traumatic brain injuries @ the LATimes

They can’t be set like a bone or staunched like a bleed. They can be difficult even to detect, but the military and others are working to improve care.

Larry Ewing’s life changed last year on a construction site in Victorville; Larry Carr’s changed in 2004 on a road in Iraq. Unlikely brothers in arms, both men now share the same invisible wound — traumatic brain injury.

They tire easily, forget often and lose their balance and concentration without warning. They struggle to make peace with personality changes that have made them barely recognizable to loved ones.

Read the whole story here

Diving Into My MRI

I spent time yesterday studying my MRI, comparing my brain with pictures of normal MRI’s I found online at Google images. What a treasure trove Google is! Just being able to find pictures of what “normal” looks like has been a great boon to me.

Looking at MRIs can be very trippy, and looking at my own brain is kind of spooky. From looking at it, the untrained eye could easily become very disoriented and alarmed. But knowing what other normal MRIs look like is very helpful. How else would I know that I’m not a freak of nature? The brain is just so fascinating!

It’s so great to find descriptions of the normal brain MRIs, since it can be hard to figure out what you’re looking at. I’ve got a used textbook on neuroscience I picked up, as well as a copy of Netter’s Atlas of Human Anatomy, which is a hefty tome of highly detailed drawings (done by Dr. Netter) of virtually every part of the human body, which also have every little piece clearly marked and labelled. I look at my MRI, then I consult my Netter’s book, then I Google the part of my brain that I think I’m looking at and read about it, and then consult my neuroscience textbook, to read more in-depth information that’s at a student level. Fascinating.

But I’m surprised to be having such a hard time finding information on reading MRIs. Maybe I’m not looking in the right places. Maybe that type of information is too advanced to be safe to release into the public, lest we all fire our radiologists, start reading our own MRIs, and jump to conclusions about ourselves. I’ve already had people look askance at me, when I told them I was going to be studying my MRI. They clearly seemed to think that I’m not qualified to do it, but I figure, why let that stop me? I’m not getting paid by anyone to ply that trade, and I’m only interested in my own situation, and it’s really just for my own gratification, so I’m not letting their skepticism stop me. It’s my body. I’ll study it to my heart’s content.

I know there’s no substitute for a qualified neurologist or radiologist, but I really need to understand what’s going on with me, and nobody seems to have the time to spend with me to make sure I’m clear on what’s going on. It’s very discouraging to have this level of testing done, only to not be able to find someone to help me understand it. The neuro I saw a week ago wouldn’t give me any more information, other than that my tests read as normal. I asked if they could show me the film, but they brushed me off. Maybe they thought I’d be looking for something that doesn’t exist… malingering and all that. I’m not malingering. I’m curious! And honestly, I don’t want to milk this and make myself out to be sicker than I am. I just want to know why my life experience is so different from what I hear everyone else describing. I want to know why I have the many, many issues I’ve got. I want to know what makes my brain unique — and treat that uniqueness as a strength, not a weakness. And having MRI images to help me gain just a little more insight into my situation seems like a great opportunity to learn more… even/especially if what I learn is that my variations on experience are “within normal range” and not the sort of thing I need to be concerned about.

I did find some pictures of my brain that I have questions about. Places where there are asymmetries and/or dark/light spots that might be old injuries or some abnormality. The part of me that’s been on high alert — or hovering around there — is eager to run off to a neuro to get the spots and dots and bright places explained… to explain how the asymmetries in my brain might translate to some irregularities in how my mind works. I know I need to calm down, get some rest, let it all sink in. There’s no tremendous hurry, now that I know that I’m not in imminent danger from a brain tumor or MS or some other terrible neurological condition. I can relax, now. And I need to make more of an effort at doing that.

In the meantime, while I recover from my over-excitabilities, I’ll think about my next steps. Study normal MRIs online, look around, just do the whole visual image thing, getting my eyes used to the sight of MRIs, so when I do get a chance to talk to a neuro about my results, I can sound at least moderately intelligent. I’m thinking about contacting that last neuro I went to see — the one who treated me like I was looking for drugs, who has since apparently recanted their attitude towards me and offered to help me “in any way” they can. I may give them another chance — but next time, take someone I trust with me, and ask the neuro to just walk me through the high-level points of my MRI. There are some things that are grabbing my attention, and I would like a little bit of an explanation.

I really need someone to read it who knows how to interpret the orientation of the images. I think MRIs may give you a mirror image of a body part, so the left side of the picture is actually the right side. At least, that’s the impression I get from reading descriptions of MRIs that show clear anomalies on the left side… but the text talks about right-side issues. It gets confusing. One side of my brain is shaped a little differently than the other, and I’m not sure if my right side is lop-sided, or if it’s my left. I think it makes a difference, too, which side is varied from the “norm” — left and right sides have different functionality, or so I understand, and if I’ve got developmental issues with one side of my brain, then knowing about them might help me better understand and manage my own issues.

It could be that I’m on some wild goose chase, and that all the differences in my brain are in fact quite normal. But looking at my pictures and comparing them with other MRIs, my head is kind of lop-sided, and one side of my brain has a noticeably different angle than the other side — between the lower frontal/parietal lobes and the temporal lobe that sits beneath it. I’ve got some asymmetrical bulges, and in some places, one part of my brain looks like it’s been crowded by another part that is not shaped the same way as others’ normal pix. It is considerably wider and looks bigger than I’ve seen elsewhere, so that just makes me wonder.

I don’t think it’s a bad thing, having parts of my brain differently arranged than the norm. If anything, it’s probably an advantage. Even if my brain developed differently over the course of my life, it hasn’t completely stopped me from living my life, and no one would probably ever guess that it’s developmentally different. I’ve been far too successful in my life, far too resilient, far too capable, far too adaptable, far too effective, all across the board, for any sort of developmental differences to be a liability. If anything, my differences are a strength. And I’d never part with them. Not at all.

Looking at all these “normal MRI” pix, I have to wonder… What is normal, anyway? If you think about it, the chances of anyone turning out the same way as other people are just so slim. The human body is an amazingly intricate and sensitive system that can be impacted by unseen, invisible forces that we don’t recognize for a long time, if we recognize them at all. We’ve got billions and billions of cells constantly growing and changing and multiplying, we’ve got tons of distinct body parts, we’ve got so many different bodily functions, many of them invisible to us. And we’ve got not only our internal world but our external world to deal with and factor in. Some days, I’m amazed that the human race — or, for that matter, any living creature — makes it through a single day.

Lots can go wrong. Lots can change us. Lots can affect us and our development. But variations are what keep the human race viable. The healthiest living systems have a lot of variety in them, and I would expect that variations in brain development are critical for a healthy system, as well. Even if those variations appear to be “disabilities” or some other sort of rare deviation. The human brain is an amazing organ, and not only can it do things we cannot even begin to imagine possible, but it can also accommodate a whole lot of additional variations and bounce back from injuries, with neuroplasticity and remapping functions and other mechanisms we haven’t even begun to name. (I haven’t done a plug for The Brain That Changes Itself by Norman Doidge, in a few months, so I’ll mention it here — if you have doubts about the ability of the brain to adapt, then you should definitely check it out.)

So, even if my brain is developmentally anomalous, and even if it got broken along the way with those hits and falls and accidents, and even if it gets tired and overwhelmed and doesn’t know where it is, sometimes, it’s still mine. It’s what I have to work with. And so far, injuries and accidents notwithstanding, it’s still going strong.

EEG and MRI are both normal!

Woo hoo!

I had a visit with my new neuro on Monday, and they tell me that my EEG and MRI both read as NORMAL.

There is no sign of a brain tumor.

There is no sign of MS.

There is no sign of degenerative disease.

I’m way symmetrical and looking good.

At last, I’ve got some actual testing and numbers to show for all this. Enough of the guesswork — I’ve got plenty of notes and detailed observations about my life, but no doctor apparently has the time or inclination to sort through them all.

Plus, with my over-the-top attention to detail and fixation on things that are experientially important (but probably medically insignificant), who knows if anything I’ve recorded is even any use to them at all?

God, I love minutiae. But it doesn’t love me 😉

Anyway, I’m trying really hard to stay positive through all this. I think that part of me would have liked to see at least a little bit of “variation” on my test results, so I have concrete proof that something unusual is “up” with me.

But this is actually one of the things that makes TBI such a conundrum for folks — both medical doctors and people who experience it. Your test results can come back looking great, your CAT scan, your MRI, and your EEG can all come back normal. But there are real issues hidden under the surface that emerge over time and with varying degrees of difficulty.

And those issues can look like seizures or mental illness or ADD or OCD or some of the other “alphabet” conditions that are swimming around out there.

Or, worst of all, they can be interpreted as a lack of will, being a “bad seed”, being “sinful”, or old-fashioned “character defects” that have little or nothing to do with character and have everything to do with the brain not behaving as it should.

And it can make you crazy. Personally, I wouldn’t be surprised to learn that mental illness can emerge as a result of the stress and strain of dealing with TBI… with or without knowing it.

Well, I would love to write more… and I really want to. But I’ve got to get ready for work and stop at the bank to close the business bank account I opened back before I realized that I wasn’t nearly as capable as I thought I was, and my MBTI was propelling me forward in life, fueled by anxiety, drive, aggression, and a deep-seated need to prove to myself and the world that I was really doing very well… when in fact, I wasn’t.

I know now that the complicated tasks involved with running a business are well beyond my broken brain. I may be able to get back some of my functionality with some speech/occupational therapy, but that’s a ways off in the futur. Right now, it’s time for me to let go of that unrealistic drive and work with the limitations I have. In a way, it’s a huge relief. There are plenty of other ways I can prove my self-worth to myself and the world that don’t involve adminstrative paperwork and filing quarterly taxes 😉

Note: This was cross-posted at Daily Strength

Prepping for my neuro visit tomorrow

I’ve got another neuro visit tomorrow — this one is finally a substantial one, when I’ll actually be reviewing the results of my MRI and my EEG. It’s been about a month since I got my MRI, and it’s been nearly 3 weeks since my EEG, and the suspense has been really intense at times.

In my more dramatic moments, part of me thinks, “Today is the last ‘normal’ day/week of my life.” And I get all worked up, thinking that these test results might come back with terrible news or some sign of a horrible condition/disease/tumor/whatever that will sideline me permanently — or at least turn my life into one big detour.

I worry that I won’t be fully functional anymore. That I’ll have to invest all this extra time and energy in overcoming a real issue that I’ve blissfully ignored for a long time. That I’ll be officially disabled. That I’ll be “less than human” and have to live a second-rate life as a result of what the pictures of my brain show.

I also worry that they won’t find anything at all… that I’ll turn out to be crazy and people will look at me like I’m just looking for attention… making things up… malingering… defrauding professional service providers.

Worst of all, I think, would be getting inconclusive results that will waylay my energy and keep me pre-occupied trying to track down the root cause of stuff that’s been getting in my way for a long time, but I’ve been able to brush off and minimize until the past year or so.

I’d almost rather get no results than inconclusive ones. But whatever happens, happens. And I’ll just deal with whatever comes up. I always do.

This waiting around for test results is really exhausting. Especially since I never got any medical attention for any of my multiple TBI’s, and I don’t have a lot of reliable medical records describing my symptoms and issues in medical jargon-y detail. I’ve never been able to articulate my issues to doctors with any level of accuracy, and most of the time, I’ve just given up and said, “Oh, forget it — it’s not that bad, really…” and went off to lick my wounds where I was safe and warm and able to tend to myself and my problems on my own terms.

I swear, this cognitive-challenge/communication-difficulty stuff just makes me nuts. I have a hell of a time articulating my issues out loud to doctors, who are all too often looking for medical data and/or some Latin-based vocabulary in order to properly assess my situation. I don’t know Latin, and I don’t have medical records that show evidence of my injuries. All I have is my life experience and a muddled, garbled mish-mash of out-loud observations that don’t come across right, when I’m talking to someone who doesn’t know me personally (and even if they do, can’t for the life of them imagine that I’ve actually been injured). Absent concrete data, I’m out of luck… so, I’ve been largely resigned over the years to just being out of luck.

Oh, well… what’s next? Life is waiting…

But tomorrow, I will actually be having a discussion with a doctor about real, honest-to-goodness medical test results. Imagine that. I am really looking forward to it. I’m looking forward to it so much that I’ve been studying up on MRI’s and EEG’s and learning to recognize what they show.

I found a couple of great sites for learning about them — with plenty of pictures, which I desperately need.

There’s the section on Electroencephalography and Evoked Potentials followed by their Electroencephalography Atlas over at Medline. I have been studying the page on Normal Awake EEG
so I know what I’m looking at, when the doctor shows me what’s going on with me. I’m studying the normal EEG, as well as other types, so I can tell the difference — if there is any — between what my EEG looks like and what a normal one would look like.

Normal Awake EEG : A 10-second segment showing a well-formed and well-regulated alpha rhythm at 9 Hz.

I’ve also been studying MRI’s over at Harvard’s Whole Brain Atlas, which shows what a normal MRI looks like — with the different slices — so that when I look at my own MRI, I can see if/how it differs from how it “should” look.

They have MRI slices from different scenarios —

• Normal Brain
• Cerebrovascular Disease (stroke or “brain attack”)
• Neoplastic Disease (brain tumor)
• Degenerative Disease
• Inflammatory or Infectious Disease

And you can look at the slices from different angles, which is way cool!

I’ve been studying the normal brain MRI slices, so I am better able to understand what — if anything — is wrong with my gourd.

Now, on a wireless or dialup connection, the images load a little slowly, but on broadband/cable modem, they’re speedy.

Okay, so I know I’m a bit of a nerd/geek, but this just fascinates me. I’m also studying EEG electrode placement patterns, so when I look at my own EEG, if there is any abnormal activity, I can see what area of my brain it takes place in.

Electrodes are placed on 10-20 different areas of the scalp, and they’re lettered/numbered by position. F means Frontal Lobe, T means Temporal Lobe, O means Occipital Lobe, P means Parietal Lobe, and combinations of them mean the electrodes are getting data from more than one lobe. The numbers are odd on the left side of the head and are even on the right side. Here’s an image I’ve been studying:

I think it’s fascinating. And I have a lot to learn. I think I’ll get myself a balloon and blow it up, then write all the electrode numbers on the balloon with a permanent marker, so I have a 3D version of the placement to take with me to the doctor. I’ll let the air out of the balloon, so I can take it with me easily and then blow it up at the doctor’s office so I can see what’s up, when they start talking about the different readings of my brain.

Of course, this may be moot, if my EEG comes back perfectly normal, but in case it doesn’t, I would like to understand where/how/why things are ‘off’ with me… what it means… and if/how any of my prior TBIs have specifically impacted certain parts of my brain.

This stuff just fascinates me. It’s a lot to take in, and it can actually be pretty serious, but for now I’m going to entertain myself… not to mention distract myself from all the different scenarios my broken brain is coming up with.

Sometimes the inside of my head is a scary place to be.

EEGs show brain differences between poor and rich kids

News from UC Berkeley highlights recent research that seems pretty important to me…

BERKELEY — University of California, Berkeley, researchers have shown for the first time that the brains of low-income children function differently from the brains of high-income kids.

In a study recently accepted for publication by the Journal of Cognitive Neuroscience, scientists at UC Berkeley’s Helen Wills Neuroscience Institute and the School of Public Health report that normal 9- and 10-year-olds differing only in socioeconomic status have detectable differences in the response of their prefrontal cortex, the part of the brain that is critical for problem solving and creativity.

You can read the entire article here.

Personally, I’m not sure why this is so surprising to people. We’ve known for years that trauma causes changes to the brain — both chemically and cognitively and physically. And poverty contributes to trauma. Of course, there may be a chicken-or-the-egg connection — which comes first, the poverty or the impaired brain function? — but at least someone is getting tangible measurements about the interplay between socioeconomic status and cognitive functioning.

This puts a new spin on haves and have-nots.