Archive for the ‘Uncategorized’ Category

Another beautiful image from brain science

Wednesday, August 6th, 2014

Y’all know how much I like the beautiful images coming from neuroimaging and microscopy of the brain. Here’s one that was posted recently at the website BrainFacts.org, showing (in green) cells in mouse motor cortex expressing a gene transcription factor called Fezf2. The grey cells show what changes come about in cell structure after Fezf2 is expressed in the cell, putting out long, branching extensions called dendrites (from the Greek δένδρον, or “tree”). Dendrites are the part of the neuron that receives incoming signals from other neurons. When the dendritic tree expands and branches, it increases the cell’s capacity to make connections with, and be influenced by, other neurons.

But I’m really just posting this because it’s pretty. Ain’t it just?


So. Let me introduce you to my friend LORETA.

Monday, July 21st, 2014

It’s not what you think. Although I do know a really nice woman named Loreta. A colleague from a ways back. But I digress. What I’m talking about is LORETA, with capitals. It’s poised to transform the field of neurofeedback completely.

LORETA stands for Low Resolution Electromagnetic Tomography – I know, the acronym doesn’t really work, but “LORETA” is way nicer than “LRET”. I mean, c’mon, you can’t even pronounce “LRET”. LORETA is what is known mathematically as an “inverse solution”. That is, it’s a means of mathematically reconstructing the source or sources of scalp-recorded EEG patterns, deep within the three-dimensional space inside the skull. That is, inverse solutions aim at identifying where in the brain the stuff is happening that is being picked up as electrical fields on the surface of the head. I’ll explain:

EEG in its raw form looks like this. Each electrode picks up a complex, oscillating signal from the brain tissue underneath it, and the oscillations are plotted across time, like this:

This is the EEG that neurologists read. Now, for the purposes of neurofeedback, we analyse the EEG waves into their component oscillating frequencies and compare the size (amplitude) and scalp distribution of those oscillations to a normative database. For the gentleman depicted here, who is in his thirties, the EEG waves contained an abundance of activity (relative to other people his age) in the range between about 12 and 14 cycles per second, or 12 to 14 Hz. In the database output, that looked like this:

The yellow and orange areas are where, on my client’s scalp, the brain waves at these particular frequencies exceeded the amplitude that is considered normal compared to the EEG of other people his age. Notice how there seems to be something going on in the back half his head, maybe a little more on the right side than the left.

Now, that already provides us with a lot of information—especially given accumulated clinical wisdom that says an overabundance of activity in this frequency range in the back of the head is associated with anxiety (this guy was very anxious). But it doesn’t tell us where exactly in the brain all that 12 to 14 Hz activity is really coming from.

That’s where LORETA comes in. The invention of a neuroscientist at the University of Zurich named Roberto Pascual-Marqui, LORETA is a mathematical solution that estimates—as it turns out with a high degree of accuracy—exactly where, in three dimensions deep within the brain, the source of the activity measured on the scalp is. So, in the case of my client, here’s a depiction of which part of the brain was producing the most deviant of activity at 13 Hz:

The LORETA analysis superimposes the estimated locations of activity onto a standard image of the brain, and allows us to spot the location of the abnormal activity with remarkable accuracy. The images shown here are likes slices made by a big saw (not to be all macabre about it): one horizontal, one vertical along the long axis of the brain (perpendicular to a line drawn between the ears) and one vertical, crossing the long axis of the brain at ninety degrees (parallel to a line drawn between the ears). This three-dimensional “slicing” of the brain is the way all imaging techniques work. It is, in fact, where the word tomography comes from; literally from the ancient Greek, “slice-writing”. Here’s what the same information looks like on an image of a whole, intact brain:

What LORETA allows us to do, then, is to identify with increased spatial accuracy where the patterns of brain activity observable as scalp EEG originate. Rather than looking at a smeared map of activity spread across a wide area of scalp, we can see in three dimensions where that activity actually originates in the brain. From there we can make connections to our knowledge about what locations and networks in the brain are involved in what sorts of functions. In this case, the area producing the most aberrant 13-Hz activity is the right temporoparietal junction (TPJ), which is known to be involved in responding to stimuli that are unexpected, but that have special behavioral importance or salience to the individual. Taking this information, along with the symptoms and complaints with which the individual comes to us, we can identify the structures and networks most likely to be contributing to their problems.

So, LORETA allows us to see with more precision where the sources of scalp-recorded EEG really are in the brain, even if they’re buried quite deep in the cranial vault. Want to know something even cooler? Stay tuned…

Casual marijuana use among young adults leads to structural brain abnormalities

Wednesday, May 14th, 2014

Came across this study published last month in the Journal of Neuroscience. The study’s authors, led by Jodi Gilman of Harvard Medical School, looked at whether marijuana, used in typical quantities, is associated with any structural brain changes among users between the ages of 18 and 25. Previous research had shown that administration of THC (the psychoactive component of marijuana) to rats results in brain changes, and that extremely heavy use among humans can also lead to brain abnormalities. However, to date no studies had shown whether more typical usage patterns among young human adults were associated with any brain changes.

The authors compared MRI scans between 20 casual marijuana users and 20 other young people, matched to the marijuana group on the usual demographic variables. They found—perhaps remarkably considering the small sample—pronounced differences between the marijuana group and the matched controls. In fact, every single member of the marijuana group, even those who smoked pot only once a week, showed the same pattern of structural brain differences from the control subjects. Furthermore, these brain differences were correlated with usage patterns, such that they were more pronounced among those who used the drug more frequently.

The specific differences were that the users exhibited greater grey matter density (more cells packed into a given volume) in the left nucleus accumbens and the surrounding cortex, including the hypothalamus and the left amygdala. They also showed abnormalities in the morphometry (shape) of the left nucleus accumbens and right amygdala. Now, these are not structures that one wants to mess around with. They’re critical for the processing of information related to emotion and motivation, and the nucleus accumbens in particular is associated with the generation of reward motivation – that is, the ability of a reward stimulus to influence future behavior aimed at achieving further reward. The amygdala, of course, is important for the shaping of emotional experience, as well as the influence of emotional experiences on behavior.

We seem to be on a steady track toward the full mainstreaming of marijuana in our society. The drug is being used extremely widely now, especially among teens, and in popular culture it’s consistently portrayed as a harmless form of recreation. Legislatures are under pressure to legalize its use, the outcome of which now seems to be pretty much a foregone conclusion. But this study shows that marijuana is a more powerful and potentially damaging substance than is generally thought. The study suggests that even light use brings about quite profound changes in brain structure (and, consequently, in brain function). Moreover, the anatomical structures affected by the drug line up, in kind of a scary way, with the most frequently made behavioral observations about pot users: that they seem blunted in their motivation, unambitious, listless. I’ve seen these qualities in many of my own clients who use marijuana.

Listen, it’s easy to think of those qualities as charming and entertaining. So many movies have a lovable-pothead character who is portrayed as almost a personification of the drug itself: fun, mostly harmless, kind of goofy.

But what if the brain changes that are brought about by even casual pot use result in serious motivational deficits, deficits that make it harder for the person to persist with his studies, to enjoy life when not high, to think, remember, and make decisions? How will that affect individual lives? How will it affect relationships, the workforce, the economy? Zoinks!

See what I mean about consent being flimsy?

Tuesday, April 8th, 2014

Not about the brain at all, but it illustrates the point I made in my last post. Belgian physician calls for euthanasia to be applied without the need for such cumbersome requirements as, you know, the patient actually agreeing to it. It’s in French, but Google translate makes it partially intelligible.

Into every life a little rain must fall…

Monday, March 17th, 2014

…but can you please just refrain from posting about it on Facebook? Because it bums me out. And it’s sunny here.

This recent study, published in the journal PLOS One, put together weather data and Facebook posts in American cities. The authors wanted to test a few hypotheses having to do with the impact of a variable like weather not only on people’s state of mind, but on the state of mind of members of their social network. First, they determined that people’s Facebook posts on rainy days tend to be less positive in tone than on non-rainy days. Specifically, on rainy days there were 1.19 percent fewer positively toned Facebook posts, and 1.16 percent more negatively toned posts, than on non-rainy days. That in itself isn’t terribly surprising, except maybe that the effect is pretty small. Indomitable folks, those Americans. Besides, they’re not gonna stop the rain by complainin’, am I right?

Anyway, that wasn’t the interesting part. This was the interesting part: on those same days, people’s positive and negative posts were impacted by the weather in their friends’ cities. Based on the models they constructed from the data, the authors estimated that a rainy day in New York City directly results in an extra 1500 negative posts by New Yorkers, and also results in about an extra 700 negative posts by their Facebook friends in other cities, irrespective of the weather there. Here’s a figure from their study that shows, for each city, the effect of rain in that city, as well as the (indirect) effect of rain when it happens elsewhere.

This is all direct evidence of an emotional contagion effect that occurs across social networks, and the authors argue that social media may serve to amplify natural social contagion effects by giving people more and quicker access than they would otherwise have to the emotional states of other people, even people who are miles away. This, they speculate, may result in “greater spikes in global emotion that could generate increased volatility in everything from political systems to financial markets”. Boy, that’s not at all scary, is it?

Diffusion-weighted MRI image of the human brain

Wednesday, March 12th, 2014

This picture shows up as a finalist in the Wellcome Image Awards for 2014 (check out the rest, they’re cool!). It shows an image of the connecting fibres in the human brain (I mentioned those in my last post), captured using MRI diffusion-weighted imaging. This type of imaging captures the position and direction of fibres in the brain by capitalizing on the fact that water molecules move more easily along fibres than across them. In the image the front of the head is to the right, and the left side of the head is at the top. The fibres are colour-coded to show you their direction in three dimensions: green ones run front to back along the main axis of the brain, red ones run left to right between the ears, and blue ones run top to bottom, between crown and neck. I don’t know about you, but I find images like this breathtakingly beautiful:

Diffusion weighted imaging has been an important tool recently, as neuroscience has enlarged its emphasis from the functions of particular brain structures to the way these structures are joined together, structurally and functionally, into networks. Scientists identify these networks structurally using imaging such as is shown here. They also have some cool ways of identifying them functionally, by noting which parts of the brain tend to wax and wane together across time in their oxygen uptake while a person is lying in an MRI scanner and doing some sort of task. The premise is that areas that consistently “light up” (become active) together are working together.

There’s been a lot of really neat work in this area, with several networks now reliably identified and characterized in terms of their participating brain areas and their probable functions. For example, there’s the pioneering observation of a network called the Default Mode Network, which was first characterized when neurologist Marcus Raichle and colleagues noticed that the brain always seems to be shutting off the same areas when people are in the scanner doing an experimental task. Raichle got curious about these areas, and found that they’re active when a person is not asked to engage in any task in particular, but simply lying still in the scanner. More recent work has shown that the DMN isn’t just an idling state, though: it also activates in some states of focused but inwardly-directed attention, such as thinking thoughts about oneself or recalling autobiographical events. The other thing about the DMN that’s really interesting from the perspective of psychopathology and neurology is that a lot of clinical conditions are associated with a failure to deactivate the DMN when it’s supposed to quiet down and let other, more externally directed networks do their thing. It just keeps chugging along, interfering with the external allocation of attention, which researchers think may be why so many different conditions have impaired atttention as one of their features.

Thinning of cortex correlates with changes in IQ

Wednesday, March 5th, 2014

This article describes a recent multi-site study that measured changes in children’s brains as they aged, and correlated those changes with increases or decreases in their general intelligence, as measured by their IQ. The study was published in January in the journal NeuroImage by Miguel Burgaleta, Wendy Johnson, Debra Waber, Roberto Colom and Sherif Karama. The authors compared the thickness of the brain’s cortex in children and adolescents at a two-year interval, to provide a snapshot of their development at those two time points. Cortex is Latin for “bark”, as in tree bark. It refers to the outermost layer of brain tissue, which is grey in colour and distinct from the white matter that lies underneath it. The cortex is basically where most of the computational action happens in the brain. Much of the remaining brain tissue enclosed by this “bark” consists of fibres connecting cortex to cortex, cortex to deep brain structures, and cortex to the rest of the body.

As adolescents develop, the thickness of their cortex generally decreases, a process of refinement that supports their ongoing development. What this study showed was that some people have more thinning than others in particular brain areas. Those who had moderate thinning in those areas (mostly on the left side of the brain, in front of the sensorimotor strip) maintained a similar IQ score across the two-year gap, while those who had extreme thinning showed a drop in IQ scores across the two-year interval. Interestingly, some had no thinning at all, or even a little bit of thickening, and these individuals showed increases in their IQ across the two-year period. Here’s a figure from the study showing which part of the brain showed correlations between cortex thinning and IQ changes, and what those changes were for the various IQ change groups (those who showed a decrease in IQ, stable IQ, or an increase in IQ).

The implications? Well, there are a few. One is that IQ isn’t always stable across time—although we psychologists generally assume that it will be, and that any changes we do see are the result of random measurement error. It appears that people sometimes actually get smarter, or less smart, and that these changes have real, solid neurological reasons behind them. Another is that the left frontal cortex seems particularly associated with intelligence, more so than other brain areas, although there is obviously a lot of contribution from a lot of intracranial neighbourhoods.

Best of all, I will now have a ready answer the next time my wife refers to me as being “a little bit thick in the head”.

More beauty. Sort of.

Friday, February 28th, 2014

Just saw this little bit in Scientific American. It summarizes a study published last fall in the journal Social Cognitive and Affective Neuroscience by a team of Italian researchers. In the study the researchers found that stimulating the left dorsolateral prefrontal cortex (lDLPFC) with transcranial direct current stimulation (tDCS – sorry, alphabet soup today) led to changes in their judgements of the aesthetic beauty of things they were looking at.

Specifically, the researchers had subjects rate how much they liked each of a set of paintings and photographs, then undergo either real or sham (fake) tDCS for 20 minutes, then re-rate their liking for the pictures. tDCS is a fascinating bit of cheap, simple technology that allows noninvasive stimulation of a particular bit of brain real estate, by passing a very small DC current through an electrode held against the scalp. Anyway, these folks sat and watched a movie for 20 minutes while having their left DLPFC either stimulated for real, or hooked up to a stimulator that was shut off soon after it started; then they re-rated the pictures. The result was that they liked the pictures better after real stimulation than before, but their ratings didn’t change after they received fake stimulation. Interestingly, the effect only held for representational art or photography (i.e., pictures of, you know, actual stuff), but not for abstract art. Which kind of confirms what I’ve always thought about how possible it is to actually like abstract art. Even with neuro-enhancement you can’t quite get there.

Now, the site of stimulation was particularly interesting. The left DLPFC is a favourite target for interventions aimed at increasing positive emotion. It remains the main go-to target for repetitive transcranial magnetic stimulation (rTMS – I know, more letters) for depression. Neurofeedback protocols aimed at increasing activation of left-hemisphere structures, and particularly the left DLPFC, have also shown promise in relieving symptoms of depression. So it seems that there’s a connection between positive affect in general and aesthetic appreciation in particular. I don’t know much about all that. But I know what I like.

Dementia

Wednesday, February 19th, 2014

Here’s another infographic. This one’s on dementia, and it’s very informative. Dementia is shaping up to be the public health issue of the next several decades. We have a huge number of people entering old age in the next little while, and that means a lot of dementia. As the graphic shows, dementia requires a great deal of intensive supervision and expensive health services, not to mention a lot of patience and love on the part of family members.

Dementia

Source: MBA-Healthcare-Management.com

Another new study shows that neurofeedback is effective for ADHD

Tuesday, February 18th, 2014

Here’s another study that shows how a venerable neurofeedback protocol that’s been around for quite a while (enhancing EEG wave activity in the Beta frequency while suppressing activity in the Theta frequency) reduces symptoms of inattention and hyperactivity among children with ADHD. Check it out, and take a look around the SharpBrains website while you’re at it! It’s a treasure trove of information about what works and doesn’t work when it comes to brain health and cognitive fitness.