Posts Tagged ‘Research’

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This past friday, I attended my first meditation session at my new yoga school.  I love this school and hope – someday – to make it through the full Ashtanga series and other sequences the instructors do.  In the meantime, I found myself sitting on my folded up blanket, letting my mind wander, listening to my breath and just trying to enjoy the moment.

What a wonderful experience it was … it felt great!  … I think I my have even given my brain a rest. A simple kindness to repay it for all it has done for me!

Although I did not know what I was supposed to be “doing” during meditation, the experience itself has me hooked and fascinated with a new research article, “Genetic control over the resting brain” [doi: 10.1073/pnas.0909969107]  by David Glahn and colleages.

Reading this paper, I learned that my brain “at rest” is really very active with neural activity in a series of interconnected circuits known as the default network.  Moreover, the research team finds that many of these interconnected circuits fire together in a way that is significantly influenced by genetic factors (overall heritability of about 0.42).  By analyzing the resting state (lay in the MRI and let your mind wander) patterns of activity in 333 folks from extended pedigrees, the team shows that certain interconnections (neural activity between 2 or more regions) within the default network are more highly correlated in people who are more related to each other.  For example, the left parahippocampal region was genetically correlated with many of the other brain areas in the default network.

Of course, these genetic effects on resting state connectivity are far from determinative, and the authors noted that some interconnections within the default network were more sensitive to environmental factors – such as functional connectivity between right temporal-parietal & posterior cingulate/precuneus & medial prefronal cortex.

Wow, so my resting state activity must – at some level – as a partial product of my genome – be rather unique and special.  It certainly felt that way as my mind wandered freely during meditation class. The authors point out that their heritability study lays more groundwork for follow-up gene hunting expeditions to isolate specific genetic variants.  This will be very exciting!

Some other items from their paper that I’ll be pondering in my next meditation class are the facts that these default neural networks are already present in the infant brain!  and in our non-human primate cousins (even when they are not conscious)!  Whoa!  These genetics & resting-state brain studies will really push our sense of what it means to be human, to be unique, to be interconnected by a common (genetic) thread from generation to generation over vast spatial and temporal distances (is this karma of sorts?).

I suppose yogis & other practitioners of meditation might be bemused at this recent avenue of “cutting edge” scientific inquiry – I mean – duh?!  of course, it makes sense that by remaining calm and sitting quietly that we would discover ourselves.

Related posts here, here, here

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Few genes have been studies as intensely as apolipoprotein E (APOE).  In particular, one of its variants, the epsilon-4 allele has been especially scrutinized because it is correlated with an earlier onset (about 10 years earlier than average) of Alzheimer’s Disease.  Among the many roles of APOE – its just a tiny cholesterol binding protein – are those as participant in synaptic plasticity, early neural development, damage-response and other processes – all of which share the need for the synthesis and movement of neuronal membranes (see the fluid mosaic model) and their component parts – such as cholesterol.   Hence, whenever neural membranes are being synthesized (plasticity & development) or damaged (overstimulation and other sources of oxidative damage) the tiny APOE is there to help with its membrane stabilizing cholesterol molecule in hand. Over the course of a lifetime, routine damage to neuronal membranes adds up (particularly in the hippocampus where constant storage-recall memory functions place enormous demands on synaptic plasticity systems), and individuals (such as epsilon-4 carriers) may simply show more wear-and-tear because their version of APOE is not as optimal as the other forms (epsilon-2 and -3).

apoeWith this etiological model in mind, perhaps you would like to take better care of you cell membranes (much like your car mechanic implores to change your car’s spark plugs and oil to keep the engine clean on the inside).  Moreover, perhaps you would like to do-so especially if you knew that your APOE system was less optimal than average.  Indeed, results from the recent REVEAL study suggest that folks who are in their 50’s are not unduly distressed to make this genetic inquiry and find out their genotypic status at this APOE polymorphism – even though those who discovered that they were epsion-4 carriers reported more negative feelings, understandably.  Still, with a number of education and intervention strategies available, an optimistic outlook can prevail.

Furthermore, there are ever newer diagnostic strategies that can improve the rather weak predictive power of the genetic test.  For example, cognitive assessments that measure hippocampal-dependent aspects of memory or visual orienting have been shown to be valid predictors of subsequent dementia – even moreso in populations that carry the APOE epsilon-4 allele.  Other forms of neuroimaging that directly measure the structure and function of the hippocampus also have tremendous sensitivity (here for a broad review of imaging-genetics of AD) and can, in principle, provide a more predictive view into one’s distant future.

On the very cutting edge of this imaging-genetic crystal ball technology, lies a recent paper entitled, “Distinct patterns of brain activity in young carriers of the APOE-e4 allele” by Fillippini and colleagues [doi: 10.1073/pnas.0811879106].  Here, the research team asks whether individuals in their late 20’s show structural/functional brain differences that are related to APOE genotype.  They employ various forms of imaging analysis such as a comparison of brain activity when subjects were performing a novel vs. familiar memory task and also an analysis of so-called resting state networks – which reflect a form of temporal coherence (brain areas that oscillate in-sync with each other when subjects are lying still and doing nothing in the scanner).  For the analysis of the memory task, the team found that APOEe4 carriers showed more activation in the hippocampus as well as other brain regions like the anterior midbrain and cerebellum.  When the team analysed a particular resting state network – the default mode network – they found differences in the medial temporal lobe (containing head of the hippocampus and amygdala) as well as the medial prefronal cortex.  According to the paper, none of these differences could be explained by differences in the structure or resting perfusion of the young-adult brains in the study.

Wow, these results seem to suggest that decades before any mild cognitive impairments are observable, there are already subtle differences in the physiology of the APOEe4 brain – all of which could be detected using the data obtained in 6 minutes of rest. 6 minutes of rest and spit in a cup – what does the future hold?

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