Archive for the ‘Vagus’ Category

Haroun and the Sea of Stories cover
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Recently, I’ve been reading Brian Boyd’s new book, On the Origin of Stories, – a lengthy work that relates human evolution to our creative processes.  This line of inquiry is closely related to an interest in genetics and brain function, since links between genetic variation and brain function can be used as a starting point in phylogenetic analyses and explorations into the origins of human nature.  Human(ist)-specific genetic variants … hmmm … easier said than done – I know.

One reason why this topic may be especially complex are the very deep phylogenetic roots to human emotional regulation.  Indeed, the emotions, although we might construe to be aspects of mental life, are rather much more aspects of our physical life.  As Pliny the Elder pointed out when he opined “A merry heart doeth good like a medicine“, there is an obvious 2-way relationship between the our physical state (heart function for one) and our mental state.  Thus, our understanding of the origins of human nature (or stories, in the case of Brian Boyd) may involve deep-rooted phylogenetic explorations that dig well before homo sapiens related its first tales.

How far back?  Perhaps the paper by Porges,  “The polyvagal theory: New insights into adaptive reactions of the autonomic nervous system” [doi:10.3949/ccjm.76.s2.17] offers some advice.  He suggests that the regulation of cardiac function has been adapted within mammals to support the 2-way communication of facial expressions and heart function. To quote from Porges’ article, “A face–heart connection evolved as source nuclei of vagal pathways shifted ventrally from the older dorsal motor nucleus to the nucleus ambiguus. This resulted in an anatomical and neurophysiological linkage between neural regulation of the heart via the myelinated vagus and the special visceral efferent pathways that regulate the striated muscles of the face and head, forming an integrated social engagement system.”  More specifically, he seems to point to the myelination of the mammalian vagus nerve (other vertebrates have an unmyelinated vagus).

This is a loooong way back in evolution.  Still, it is a story well worth telling.

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