May 11, 2011

The External Pfc

Posted in consciousness, Language and Myth tagged , , , at 10:46 pm by Jeremy

This blog describes how our consciousness is under excessive control from our prefrontal cortex (pfc).  But it’s not just our own pfc that controls our consciousness.  Far more powerful is the control exercised by the external pfc,  that cumulative collection of symbolic patterns over countless generations that governs how our own brains connected up as we developed in infancy.  That’s what this section of my book, Liology: Towards An Integration of Science and Spirit, is about.

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The external pfc

With all the discussion of metaphors, you might be tempted to think that the notion of an individual’s pfc being molded by the thought structures around her is itself a metaphor, that it’s not literally describing a physical process.  However, in this case, it’s no metaphor.  The pfc of each individual infant growing up in her culture is quite literally shaped by the structures of thought that have evolved in that specific culture.

In order to see how this can be, it’s necessary to understand the basic process of how an infant’s brain matures.  In recent years, neuroscientists have made great progress in identifying these dynamics, and it’s now become clear that infant brain development is to a large extent a pruning process.  In the embryo and the newly born infant, massive amounts of neuronal connections, known as synapses, are formed quite variably and spontaneously.  As the infant gets used to certain behaviors, such as grasping, nursing or cooing, the synaptic junctions that led to a successful behavior quickly get strengthened by increased usage.  However, those connections which are never used by the infant begin to wither away.  As the infant grows, this process of synaptic reinforcement continues until some pathways are massively strengthened while countless others which turned out be useless have died out.  A useful analogy to visualize this process is an uncultivated field of tall grass through which, all of a sudden, people begin walking to get to various places they need to go.  At first, everyone’s beating about the bush, but after a while, certain trails begin to appear in the grass, as the most successful routes taken become more popular and cause the wild grass to get flattened down, so that eventually clear pathways emerge through the field.  The clearer the pathway, the more likely it is to be used by the next person, thus leading to a positive feedback cycle.  This process in the brain is sometimes referred to as synaptic pruning, because the less useful neurons and synaptic pathways are pruned away by lack of use.[1]*

Neuronal connections grow over time like trails through tall grass

This is how the pfc of each individual infant is literally molded by external factors which, as Donald describes, “can actually change the operational architecture of cognition in the individual by influencing the developing brain.”[2]  In a 2009 paper entitled “Foundations for a New Science of Learning,” one team points out that human infants remain immature for a far longer period than other animals, as the brain continues to grow throughout childhood.  This slow process of maturation permits the brain to adapt to the specific variables of the outside world through a process that they call “neural commitment,” whereby the brain’s “neural architecture and circuitry” is molded based on the “structured models” of the environment that the infant perceives.[3]  Another research team supports these findings, describing how “the extended postnatal development of the human cortex” permits “synaptic proliferation and pruning” to “restructure the maturing brain in response to the environment and to the community of practices in which development is embedded.”[4]

Because of this process, a human born in the modern world might be genetically identical to one of our ancestors born before, say, the Upper Paleolithic revolution, but if a brain scan could be performed on both individuals at maturity, they would look very different.  Cognitive neuroscientist Wolf Singer points out that “the organization of our brains is not only determined by the genes” but is also shaped by the influences of our “socio-cultural environment …  This is the reason why the fine-grained connectivity of our brains differs from that of our cave-dwelling ancestors despite the rather similar genetic dispositions.”  He explains that the differences in our brains would not be in the general layout and gross structure, but rather in the “the dense meshwork of local intracortical connections.”[5]

The external pfc is the sculptor of each individual's brain

So the brain is literally sculpted by the influences it receives in its early years.  But what’s doing the sculpting?  What I’m calling the “external pfc” is the cumulative symbolic network of meaning that’s been constructed by countless generations of minds within a given cultural tradition.  The pfc of each person born into that tradition is sculpted by the previous accumulation of symbolic meanings, and then may contribute its own unique interpretations of the inherited symbolic network to modify incrementally the external pfc for the next generation.  It’s important to understand that, although the external pfc, with its accumulation of prior meaning, is far more powerful than any individual pfc, the relationship between them is, to a certain degree, mutually interactive.  As described by one team of cognitive scientists:

The nervous system, the body and the environment are highly structured dynamical systems, coupled to each other on multiple levels.  Because they are so thoroughly enmeshed – biologically, ecologically and socially – a better conception of brain, body and environment would be as mutually embedded systems rather than as internally and externally located with respect to one another.[6]

The integration of symbolic meaning between an individual and his culture allows “human beings to, in effect, pool their cognitive resources both contemporaneously and over historical time in ways that are unique in the animal kingdom.”[7]  This symbolic interaction is the hallmark of culture and is viewed by many experts as the major driver of the massive changes that humans have brought to their environment over the millennia.  The famed evolutionary biologist, Conrad Waddington, sees as the defining characteristic of humanity “an extremely elaborate system by which the whole conceptual understanding of the past is made available to present recruits to human society.  We have here what in effect amounts to a new mode of hereditary transmission.  It may be referred to as the cultural or ‘socio-genetic’ system.”[8]

Is the external pfc, then, merely another term for what’s generally known as culture?  While there are subtle differences between the two, this is largely correct.  However, the word “culture” is often very broadly and loosely defined, and so I call it the “external pfc” to emphasize the symbolic network of meaning that interacts with the pfc of each individual growing up within a culture.  Two different definitions of culture by experts in the field will illustrate my point:

1.  “Culture is information capable of affecting individuals’ behavior that they acquire from other members of their species through teaching, imitation, and other forms of social transmission.”[9]

2.  “By cognition, I mean simply the internal structure of ideas that represent the world and that directs behaviors appropriate to the world represented.  By culture, I intend only the distributed structure of cognition, that is, the causal networking of ideas and behaviors within and between minds.”[10]

The first definition emphasizes a one-way flow from society to the individual and focuses on the behavioral, rather than cognitive, effects of cultural transmission.  There’s nothing intrinsically wrong with this definition, but it misses the dynamic I’ve been describing.  The second definition, on the other hand, points out the “distributed structure of cognition” and emphasizes a two-way flow of causal networking.   This cumulative and dynamic network of meaning “within and between minds” is what I mean by the external pfc.

However, interactive as the relationship may be between the external pfc and the individual mind, it’s certainly not a level playing field.  The external pfc is guaranteed to shape the individual’s pfc far more extensively than vice versa.  There are a number of reasons for this.  The first is that the external pfc, as a cumulative aggregation of meaning, offers a far more extensive modeling of the universe than an individual mind could ever hope to achieve.  Secondly, the individual mind is being molded when it is too new and unformed to make up its own patterns of meaning, so that by the time an individual has achieved a level of self-awareness enabling him to attempt to structure his own meaning, the neural pathways in his mind have already been largely sculpted.

Donald describes well how the process he calls “deep enculturation” begins from birth to “affect the way major parts of the executive brain become wired up during development”:

Shortly after birth, the infant is wedded to a specific culture that takes control of its cognitive development through a series of transactions.  This may sound improbable because cultural linkages are invisible to the child.  They hide behind many surrogates, such as parents, family, tribal customs, institutions, and so on.  These are the carriers of the culture, the front lines of the infant’s encounter with vast collective forces that it never sees and whose existence even the surrogates may not suspect.[11]

The impact of deep enculturation is “so close to us,” Donald notes, “that we are normally unaware of it.”  In fact, as we mature, the most structural aspects of this enculturation become embedded deep in our unconscious.  “All of our knowledge and beliefs,” write Lakoff and Johnson, “are framed in terms of a conceptual system that resides mostly in the cognitive unconscious,” which acts like a “hidden hand that shapes how we conceptualize all aspects of our experience…, how we automatically and unconsciously comprehend what we experience.”[12]

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[1] The neuroscientist Gerald Edelman is credited with first developing this understanding of infant brain development, with his theory of “neural Darwinism.”  See Rosenfield, I. (1986). “Neural Darwinism: A New Approach to Memory and Perception.” The New York Review of Books, 33(15 [Oct. 9, 1986]).  Also see Edelman, G. M., and Tononi, G. (2000). A Universe of Consciousness: How Matter Becomes Imagination, New York: Basic Books, 83-4 for a discussion in Edelman’s own words.  Separately, neuroscientist Jean-Pierre Changeux developed a similar theory of “learning by selection”; see Rosenfield, I., and Ziff, E. (2008). “How the Mind Works: Revelations.” The New York Review of Books, June 26, 2008, 62-65 for a discussion of Changeux’s approach.

[2] Donald, M. (1999). “Material Culture and Cognition: Concluding Thoughts”, in C. Renfrew and C. Scarre, (eds.), Cognition and Material Culture: the Archaeology of Symbolic Storage. Cambridge: McDonald Institute for Archaeological Research, pp. 181-187.

[3] Meltzoff, A. N., Kuhl, P. K., Movellan, J., and Sejnowski, T. J. (2009). “Foundations for a New Science of Learning.” Science, 325(17 July 2009), 284-288.

[4] Brooks, P. J., and Ragir, S. (2008). “Prolonged plasticity: Necessary and sufficient for language-ready brains.” Behavioral and Brain Sciences, 31(5 (2008)), 514-515.

[5] Singer, W. (2009). “The Brain, a Complex Self-Organizing System.” European Review, 17(2), 321-29.

[6] Thompson, E., and Varela, F. J. (2001). “Radical embodiment: neural dynamics and consciousness.” Trends in Cognitive Sciences, 5(10), 418-425.

[7] Tomasello, M. (1999). “The Human Adaptation for Culture.” Annual Review of Anthropology(28), 509-29.

[8] Waddington, C. H. (1959). “Evolutionary Systems – Animal and Human.” Nature, 183, 1634-1638.

[9] Richerson, P. J., and Boyd, R. (2005). Not By Genes Alone: How Culture Transformed Human Evolution, Chicago: University of Chicago Press.

[10] Atran, S. (2002) op .cit., 10.

[11]Donald, M. (2001). A Mind So Rare: The Evolution of Human Consciousness, New York: Norton, 211-12.

[12] Lakoff, G., and Johnson, M. (1999). Philosophy in the Flesh: The Embodied Mind and its Challenge to Western Thought, New York: Basic Books, 13.

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