Posts Tagged ‘Magnetic resonance imaging’


The above images are eigenfaces … which are statistically distilled basic components of human faces … from which ANY human face can be reconstructed as a combination of the above basic components.  It’s a great mathematical trick – particularly if you’re into the whole mass surveillance and electronic police state thing.

If you are more into the whole, helping people and medical care thing, check out the global consortia at ENIGMA who have been carrying out massive genetic and brain scanning studies – like this one involving 437,607 SNPs in 31,622 voxels in 731 subjects using their new method, vGeneWAS, to study Alzheimer’s Disease:

“We hypothesized that vGeneWAS would, in some situations, have greater power to detect associations than existing SNP-based methods. One such situation might be when a gene contains many loci with weak individual effects. In addition, we expected that vGeneWAS would have greater overall power than mass SNP-based methods, like vGWAS, because of the drastic reduction in the effective number of statistical tests performed.”

The vGeneWAS method relies on the calculation of “eigenSNPs” which are eigenvectors that describe a matrix of n subjects by m SNPs in an individual gene (an n-x-m matrix of 1’s,0’s,-1’s for aa, aA, AA genotypes).  EigenSNPs are sort of like eigenfaces insofar as eigenSNPs (which are not actual SNPs) capture the majority of variance, or the basic essence of an individual gene … but seriously, you should read the original article ’cause every stats test I ever took totally punched me in the face.

In any case, the eigenSNP-by-voxel method pulled out some legit results such as rs2373115 (where the G-allele confers risk) in the GAB2 gene  which has repeatedly been implicated in the risk of age-related late-onset Alzheimer’s Disease (in folks who carry ApoE4  rs429358(C) alleles).  The authors found that the genetic risk of AD conferred by GAB2 may arise by way of GAB2’s effect on brain structure in the periventricular areas, which have been known to be among the first brain regions to show AD-related changes (time-lapse movie of AD tissue loss in the brain).

Picture 2

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Surgeon holding scalpel.
Image by bethd821 via Flickr

Whether you are a carpenter, plumber, mechanic, electrician, surgeon or chef, your livelihood depends on a set of sturdy, reliable, well-honed, precision tools.  Similarly, neuroscientists depend on their electrodes, brain scanners, microscopes and more recently their genome sequencers.  This is because they are not just trying to dissect the brain – the physical organ – but also the psychological one.  As the billions of neurons connected by trillions of synapses process electrical impulses – a kind of neural information – it is the great endeavor of cognitive-molecular-neuro-psychology (or whatever you wish to call the art) to figure out how all of those neurons and connections come into being and how they process information in ways that lead to your personality, self-image, hopes, dreams, memories and the other wonderful aspects of your mental life.  How and why does information flow through the brain in the way it does? and how and why does it do so in different ways for different people? Some, for instance, have informally related Sigmund Freud‘s models of mental structure to a kind of plumbing wherein psychic energy was routed (or misrouted) through different structural aspects of the mind (pipes as it were).  Perhaps such a model was fitting for the great industrial era in which he lived – but perhaps not in today’s highly information-based, inter-connected and network-oriented era.  If our understanding of mental life is a product of our tools, then perhaps we should be sure that our modern tools are up to the job.

One recent paper reminded me of how important it is to double check the accuracy and precision of one’s tools was the research article, “Quantifying the heritability of task-related brain activation and performance during the N-back working memory task: A twin fMRI study” [doi:10.1016/j.biopsycho.2008.03.006] by Blokland et al..  In this report, the team summarizes the results of measurments of the brain activity – not structure – but rather activity as measured by their chosen tool, the MRI scanner.  This research team, based in UCLA and known as one of the best in the field, asks whether the so-called BOLD response (an indirect measure of neural activity) shows greater concordance in identical (monozygotic) vs. fraternal (dizygotic) twins.  To generate brain activity, the research team asked the subjects to perform a task called an N-back  workng memory task, which entails having to remember something that happend “N” times ago (click here for further explanation of N-back task or play it on your iphone).  If you’ve done this, you’ll know that its hard – maddeningly so – and it requires a lot of concentration, which, the researchers were counting on to generate activity in the prefrontal cortex.

After looking at the brain activity patterns of some 29 MZ pairs and 31 DZ pairs, the team asked if the patterns of brain activity in the lateral frontal cortex were more similar in the MZ pairs vs. the DZ pairs.  If so, then it would suggest that the scanning technology (measurement of the BOLD response) is sufficiently reliable and precise enough to detect the fraction of individual differences in brain activty that arise from additive genetic variation.  If one actually had such super-precise tool, then one could begin to dissect and tease apart aspects of human cognition that are regulated by individual genetic variation – a very super-precise and amazing tool – that might allow us to understand mental life in biologically-based terms (and not Freud’s plumbingesque analogies).  If only such a tool existed! Somewhat amazingly, the scanning tools did seem to be able to detect differences between the BOLD response correlations of MZ pairs vs. DZ pairs.  The BOLD response correlations were greater for MZ vs. DZ in the middle frontal gyrus, angular gyrus, supramarginal gyrus when activity for the 2-back task was compared to the 0-back task.  The team were cautious to extend these findings too far, since the standard deviations are large and the estimates of heritability for the BOLD response are rather low (11-36%), but, overall, the team suggests that the ability to use the fMRI methods in conjunction with genetic markers shows future promise.

Meanwhile, the literature of so-called “imaging-genetic” findings begins to grow in the literature.  I hope the tools are reliable and trustworthy enough to justify conclusions and lessons about human genetic variation and its role in mental life.  Will certainly keep this cautionary report in mind as I report on the cognitive genetics literature in the future.

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morph_slicer_demoThe brain is a wonderfully weird and strange organ to behold.  Its twists and folds, magnificent, in and of themselves, are even moreso when we contemplate that the very emotional experience of such beauty is carried out within the very folds.  Now consider the possibility of integrating these beauteous structure/function relationships with human history – via the human genome – and ask yourself if this seems like fun.  If so, check out the recent paper, “Genetic and environmental influences on the size of specific brain regions in midlife: The VETSA MRI study” [doi:10.1016/j.neuroimage.2009.09.043].

Here the research team – members of the Biomedical Informatics research Network – have carried out the largest and most comprehensive known twin study of brain structure.  By performing structural brain imaging on 404 male twin pairs (important to note here that the field still awaits a comparable female study), the team examined the differences in identical (MZ) vs. fraternal (DZ) pair correlations of the structure of some 96 different brain regions.  The authors now provide an updated structural brain map showing what structures are more or less influenced by genes vs. environment. Some of the highlights from the paper are that genes accounted for about 70% of overall brain volume, while in the cortex, genes accounted for only about 45% of cortical thickness.  Much of the environmental effects were found to be non-shared, suggesting, as expected, that individual experience can have strong effects on brain structure.  The left and right putamen showed the highest additive genetic influence, while the cingulate and temporal cortices showed rather low additive genetic influences (below 50%).

If you would like to play around with a free brain structure visualization tool, check out Slicer 3D, which can be obtained from the BIRN homepage or directly here.  I had fun this morning digitally slicing and dicing grey matter from ventricles and blood vessels.


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William Faulkner
Image via Wikipedia

What hurts more – a broken toe or a broken heart?  Ask a parent and their forlorn 15 year-old who was not invited to the party that everyone is going to, and you might get different answers.  In some cases, the internal anguish of social exclusion or estrangement, may even – paradoxically – be relieved by self-infliction of physical pain, which is construed by some neuro-psychiatrists as a coping mechanism, wherein endogenous opioids are released by the physical injury (cutting, for instance) and may then soothe the internal feeling of anguish.

While there are many social, and psychological factors pertaining to the way in which people cope with internal and external pain, a recent research article from Dr. Naomi Eisenberger’s lab sheds light on a very basic aspect of this complex process – that is – the similarities and differences of neural mechanisms underlying social and physical pain.  In their recent paper, “Variation in the μ-opioid receptor gene (OPRM1) is associated with dispositional and neural sensitivity to social rejection” [doi:10.1073/pnas.0812612106] the authors asked healthy participants to lay in an MRI scanner and play a video game of catch / toss the ball with other “real people” by way of a computer interface.  During the game, the participant was rudely socially excluded by the other two players in order to induce the feelings of social rejection.  Participants also completed an instrument known as the “Mehrabian Sensitivity to Rejection Scale” and were genotyped for an A-to-G SNP (rs1799971) located in the opioid receptor (OPRM1) gene.  Previous research as found that the G-allele of OPRM1 is less expressed and that individuals who carry the GG form tend to need higher doses of opioids to feel relief from physical pain, and GG rhesus monkeys (interestingly, we share the same ancient A-to-G polymorphism with our primate ancestors) demonstrate more distress when separated from their mothers.

The results of the study show that the participants who carry the AA genotype are somewhat less sensitive to social rejection and also show less brain activity in the anterior cingulate cortex (an area whose activity has long been associated with responses to physical pain) as well as the anterior insula (an area often times associated with unpleasant gut feelings) when excluded during the ball-toss game.  Further statistical analyses showed that the activity in the cingulate cortex was a mediator of the genetic association with rejection sensitivity – suggesting that the genetic difference exerts its effect by way of its role in the anterior cingulate cortex.   Hence, they have localized where in the brain, this particular genetic variant exerts its effect.  Very cool indeed!!

Stepping back, I can’t help but think of the difficulties people have in coping with internal anguish, which – if not understood by their peers – can, mercilessly, lead to further exclusion, estrangement and stigmatization.  Studies like this one reveal – from behavior, to brain, to genome – the basic biology of this important aspect of our social lives, and can help to reverse the marginalization of people coping with internal anguish.


The picture is of William Faulkner who is quoted, “Given the choice between the experience of pain and nothing, I would choose pain.”  I wonder if he was an AA or a G-carrier?  I feel rather lucky to find that my 23andMe profile shows an AA at this site.

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