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Posts Tagged ‘Human behavior’

C.H. Waddington provides conceptual framework for shifting influences of genes and environment in the development of mind

Posted in Uncategorized, tagged , , , , , , , , , , , , , on January 12, 2010| Leave a Comment »

Just a pointer to onetime University of Edinburgh Professor C.H. Waddington’s 1972 Gifford Lecture on framing the genes vs. environment debate of human behavior.  Although Waddington is famous for his work on population genetics and evolutionary change over time, several of his concepts are experiencing some resurgence in the neuroimaging and psychological development literatures these days.

One term, CHREOD, combines the Greek word for “determined” or “necessary” and the word for “pathway.” It describes a system that returns to a steady trajectory in contrast to homeostasis which describes a system which returns to a steady state.  Recent reviews on the development of brain structure have suggested that the “trajectory” (the actual term “chreod” hasn’t survived) as opposed to any specific time point is the essential phenotype to use for understanding how genes relate to psychological development.  Another term, CANALIZATION, refers to the ability of a population to produce the same phenotype regardless of variability in its environment or genotype.  A recent neonatal twin study found that the heritability of grey matter in neonatal humans was rather low.  However it seems to then rise until young adulthood – as genetic programs presumably kick-in – and then decline again.  Articles by neurobiologist Jay N. Giedd and colleagues have suggested that this may reflect Waddington’s idea of canalization.  The relative influence of genes vs. environment may change over time in ways that perhaps buffer against mutations and/or environmental insults to ensure the stability and robustness of functions and processes that are both appropriate for survival and necessary for future development.  Another Waddington term, EPIGENETIC LANDSCAPE, refers to the limitations on how much influence genes and environment can have on the development of a given cell or structure.  Certainly the environment can alter the differentiation, migration, connectivity, etc. of neurons by only so much.  Likewise, most genetic mutations have effects that are constrained or compensated for by the larger system as well.

Its amazing to me how well these evolutionary genetic concepts capture the issues at the nexus of of genetics and cognitive development.  From his lecture, it is clear that Waddington was not unaware of this.  Amazing to see a conceptual roadmap laid out so long ago.  Digging the book cover art as well!

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Building and maintaining synapses

Posted in Uncategorized, tagged , , , , , , , , on October 17, 2009| 1 Comment »

SfNneuroblogbadge Phrenological thinking, a popular pseudoscientific practice in the 1800’s suggested that the structure of the head and underlying brain held the clues to understanding human behavior.  Today, amidst the ongoing convergence of developmental science, molecular & biochemical science and systems-dynamical science (to name just a few), there is – of course – no single or agreed-upon level of analysis that can provide all the answers.  Circuit dynamics are wonderfully correlated with behavior, but they can be regulated by synaptic weights.  Also,  while developmental studies reveal the far reaching beauty of neuronal circuitry, such elegant wiring is of little benefit without healthy and properly regulated synaptic connections.  Genes too, can be associated with circuit dynamics and behavior, but what do these genes do?  Perchance encode proteins that help to form and regulate synapses? Synapses, synapses, synapses.  Perhaps there is a level of analysis – or a nexus – where all levels of analysis intersect?  What do we know about synapses and how these essential aspects of brain function are formed and regulated?

With this in mind I’ve been exploring the nanosymposium, “Molecular Dynamics and Regulation at Synapses” to learn more about the latest findings in this important crossroads of neurobiology.  If you’re like me, you sort of take synapses for granted and think of them as being very tiny and sort of generic.  Delve a while into the material presented at this symposium and you may come to view the lowly synapse – a single synapse – as a much larger, more complex, ever changing biochemical world unto itself.  The number of molecular players under scrutiny by the groups presenting in this one session is staggering.  GTPase activating proteins, kinases, molecular motors, receptors, proteases, cell adhesive proteins, ion channels and many others must interact according to standard biochemical and thermodynamic laws.  At this molecular-soup level, it seems rather miraculous that the core process of vessicle-to-cell membrane fusion can happen at all – let alone in the precise way needed to maintain the proper oscillatory timing needed for Hebbian plasticity and higher-level circuit properties associated with attention and memory.

For sure, this is one reason why the brain and behavior are hard to understand.  Synapses are very complex!

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