Long ago in my previous life as a fifth grade teacher right after college, I read a good many classics in early neuroscience and linguistics, books by A. R. Luria, L.S. Vygotsky, Karl Pribram, Noam Chomsky, Eric Lenneberg, etc. And reading and talking to some others I thougt then that much of our thinking was distorted by cortical chauvinism, i.e., we thought that our cortex does everything important and lower neural structures were beneath us humans. I understood two reasons for this narrow-minded view. First, and most understandable, were the technological challenges of studying and understanding subcortical structures. The cortex was more available through EEG and experimental studies of higher functions especially when combined with clinical studies following strokes, e.g. aphasias, etc., and trauma, e.g., Phineas Gage. Subcortical structures were and are much more difficult to access unless we use other animals for our studies, and this brings up the second reason for cortical chauvinism. Even back in the 1960s we thought that our minds were oh so special and that this was due to our remarkable cerebral cortex, which led to the assumption that we could learn little of the human mind by studying other animals and lower neural structures.
Thankfully these days have seen many of those myths about our specialness revealed as ignorance and we have developed quite powerful techniques for studying the entire brain. This includes the brains of our own species but also now we can study the brains of other animals and understand more about our own. Shining examples of our progress here include the work of Jaak Panksepp (of course), Frans der Waal (of course), and many others, e.g., Antonio Damasio, Michael Tomasello, Jean Decety, and many, many more. (Damasio points out the case of Phineas Gage who suffered subcortical brain injury (also involving a little cortex) who recovered virtually all of his cortically based intellectual functions yet was extremely disabled because he could not focus or make anydecision—see post 12/9/18).
A couple of ancillary developments have furthered our better understanding. Back in the days of cortical chauvinism, many thought that our intellect was powerfully rational, even logical. Scientists like Amos Tversky and Daniel Kahneman have showed how hollow that claim to a powerful rationality is, and many, like Jonathan Haidt and Antonio Damasio have shown we mostly form our opinions and then devise a rationale for them, e.g., Haidt’s description of our minds’ functioning as an intuitive dog wagging a rational tail. In Moral Tribes Joshua Greene shows how our moral principles are also thinly constructed and compares our rationalizing our moral stance to a stroke patient’s confabulatory renderings trying to explain their strange reality.
Another development would seem to leave behind the old notion of our higher cortical centers controlling the lower emotional centers in favor of understanding the remarkable interplay in 3 dimensions: up and down between horizontally organized neural structures, e.g., cortical hemispheres, limbic system, basal ganglia, etc.; back and forth between anterior (descending) and posterior (ascending) systems at various levels; and within this back and forth interplay between processing organized into dorsomedial and ventrolateral systems. (This last will need further explication below). Notice I did not mention coordination between left and right hemispheres; while our conception of this has also evolved I want to address this in a later post because my ideas here are well outside the boundaries of orthodox thinking.
Consider the connectome (see posts 1/10/15 & 8/2/16) not just as it appears cortically but in the whole of the brain. I read one of the grand visions of this in Edelman and Tononi’s book as they explained re-entrant processing (see post 7/7/16). As different systems interact up and down, back and forth, medially and laterally (and I suppose left and right), the input from one is recalibrated through further processing and returned to its source (a very relative term here) to enhance or diminish the neural patterns and forms currently in process. Yes, the cortex does inhibit subcortical centers but this inhibition can result in diminishing a pattern, e.g., anger modulation, or in enhancing a form, e.g., sharpening the figure out of the ground or permitting a positive emotion to grow stronger. We now know that GABA, a widespread inhibitory neurotransmitter, plays such a complex role, even as its counterpart, glutamate operates as a ubiquitious excitatory neurotransmitter. Ponder the connectome from this perspective for a short moment and you will understand why I think an estuary is a very apt metaphor for our brain.
Finally, back to the dorsomedial/ventrolateral organization. Lateral is along the sides of the brain or the outer surface and medial is inside more down the midline. Several research lines have coalesced into the dual loop theory, as it is sometimes called (please revisit post from 2/11/16). Now Joshua Greene in his book, Moral Tribes, proposes a dual process model for our moral decision making. Simply put, simple decisions involving oneself and one’s own tribe can be done quickly and routinely through a station in the medial system, the dorsomedial prefrontal cortex, while more difficult decisions are better resolved through a slower, more reflective process involving a station in the ventrolateral prefrontal cortex. These more difficult decisions typically involve us vs. them, i.e., a conflict between the values of two different tribes.
The lateral loop operates more reflectively because, as the great Antonio Damasio puts it, it operates with ‘as-if’ situations that involve less immediate personal involvement. I intentionally used the word ‘stations’ for both the ventrolateral prefrontal and the dorsomedial prefrontal cortical areas to signify their many connections up/down, back/front, and medial/lateral. They are interconnected with posterior cortical areas via long nerve tracts, i.e., fasciculi, and with the limbic system through a variety of connections and loops. Remember Tversky and Kahneman’s idea that we think fast by using heuristics and slowly by reflective analysis. Following Greene, I wonder if heuristics are likely more associated with the dorsomedial system while reflective considerations more with the ventrolateral. Our brains operate importantly upon two dimensions; one is old/new through the hippocampal system and the other is variant/invariant through several different systems. Their heuristics, Bourdieu’s habitus, vocabulary of meaning-sound mappings, and others are more invariant and will be found to be supported by the dorsomedial loop. Novel analyses, modulating habitual and skilled cultural actions, and the subtleties underlying individual performance, e.g., playing a sonata with passion, are supported by the ventrolateral loop. Both loops involve back and forth and up and down integrations.
Viewing the connnectome through the prisms of these three neural dimensions, up/down systems, back/front systems and dorsalmedial/ventrolateral systems shows how incredible brain functions must be to engage in the old/new and variant/invariant features of human cultural behaviors. Yes, our cortex is really magnificent but let’s not be chauvinistic here: that magnificence depends upon the connections with subcortical and autonomic systems. To purloin Daniel Dennett’s critique of consciousness as a Cartesian theatre, nothing cortical could play without the subcortical stage, props, lighting, etc. Indeed the cortex alone would not foster much of any significant activity without that stage. Without the whole embodied system a mind would be sleeping emptily. The estuarine brain really is a sort of muddy mix of salt and fresh water enlivened by a phantasmagoria of vital activity, and that is what makes it and conscious animals (& there are so many more even without a cortex similar to ours) so special.