Isn’t this just rehashed left right brain stuff that has been around for years?
Yes… and no, more than 50 years of split brain research has and continues to generate a lot of solid data. However when it comes to assessing and interpreting the data the blindingly obvious has been missed. The subject of the research, the perceptual equipment being studied is the very same equipment with the executive role of assessing the data being generated. This inevitably results in an inaccurate assessment exactly as the neurological/psychological data predicts (see Delusion Resolved page). In addition no account is taken of the well-evidenced evolutionary context, a very basic oversight that would be ridiculed in any other scenario, this again is predicted by the same neurological data.
Isn’t the split brain data simply a product of split brain research?
In other words are the observed traits simply the consequence of studying each hemisphere in isolation, the corpus callosum being physically split or one of hemispheres being damaged?
It is a reasonable point and needs to be factored in. However exactly the same traits observed in split brain subjects also exist in the ‘normal’ population, they are just not so obvious.
The summaries by David Pederson Implications of cerebral specialization to hypnotherapy and Vilayanur Ramachandran- The Evolutionary Biology of Self-Deception support the proposal that ‘split brain traits’ are part of our normal function.
A further selection of papers highlighting that these traits are endemic to normal function can be found here.
Also if the proposed condition is real then somewhat obviously it would be much easier to observe in split brain subjects or when one hemisphere is compromised. I.e. the theory predicts the symptoms of the condition will be much more obvious when studying the hemispheres in isolation etc.
Why is the left hemisphere more affected than the right hemisphere?
This is easily the most frequently asked question so will be answered in some depth. If you don’t want a long answer it is simple, each side of your typical mammalian (and reptilian) brain is genetically distinct or genetically asymmetric, always was and still is. Not surprisingly when this genetic asymmetry is transcribed (read) by your typical mammalian hormone regime this results in structural and functional asymmetry. However if you immerse your typical genetically asymmetric mammalian brain in a powerful cocktail of transcription modifying (gene/DNA reading) hormonally active compounds something very well documented can happen. If the modifying cocktail generally inhibits the activity of the typical mammalian hormone regime that is normally responsible for turning the genetically encoded asymmetry into asymmetric structure and related function the structural and functional asymmetry can diminish or even disappear.
The genetically asymmetric encoding remains, the structural asymmetry is progressively ironed out depending on the strength and activity of the modification cocktail. As hormones can read or not read genetic code at specific windows of concentration/activity it is possible to effectively switch off the asymmetry by modifying the hormone regime beyond a critical window.
More generally the answer is that it is not only the left hemisphere, our whole physical structure is affected, hormones, quality and complexity of construction materials, neuro-active fuel etc effectively dictate the precise molecular configuration and functioning of our whole physiology. Our brain is perhaps the most sensitive to any change in any of these parameters, particularly changes in the hormone regime during early development. This is where there is an asymmetric effect, each side of the archaic brain that our ‘advanced’ new brain (neo-cortex) emerged from was genetically distinct, no doubt an adaptive trait. General asymmetry between the hemispheres resulting in a degree of specialisation would be a very useful adaptation for a neural system in typical ‘survival’ configuration. (Quite how useful significant genetic/structural variation would be as a precursor to the emergence or sense of being self-aware or even if such a rare experience could have emerged unless there was structural coherence/uniformity that could facilitate a singular sense of self is another matter).
Anyway, genetic asymmetry is built in, encoded in the DNA, and by definition particularly responsive to transcription factors i.e. hormones ‘designed’ to read DNA and transcribe the genetic asymmetry into structural/functional asymmetry.
Now this is where it gets interesting, immerse the asymmetric brain in a cocktail of hormones that generally inhibit the action of the hormones designed to transcribe the asymmetry and it is possible to iron out the structural/functional asymmetry without changing the genetic encoded asymmetry. The result is the proliferation of a layer of neural tissue that is structurally and functionally ever more symmetric. Then remove the steroid inhibiting compounds and the new structure that emerged (and could only emerge) in a steroid inhibited environment is exposed to a ‘primitive’ hormone regime that will transcribe the archaic genetically encoded asymmetry in attempting to build the primitive neural system still genetically encoded. It just so happens that the archaic specialisation resulted in the left hemisphere being more responsive to the regressive steroid regime, had it been the right hemisphere the frequently asked question would be why is the right hemisphere more affected. As there is genetic asymmetry built in it was always going to affect one side more quickly than the other, it just happens to be the left.
Interestingly there is less structural/functional asymmetry (or sexual differentiation) during the juvenile phase. The sex steroids that ‘read’ the asymmetric encoding are held in check in part by our own cocktail of steroid inhibiting hormones including melatonin. The production of our own steriod inhibiting cocktail is elevated by the activity of biochemicals once abundant in our symbiotic relationship with plant developmental environments (fruit).
Isn’t there evidence for our ancestors living in non-forest environments and hunting, eating meat and cooking their food?
Yes there is significant evidence going back millions of years for our ancestors and our existing relatives inhabiting various types of forest and non-forest/non-fruit habitats and adapting their behaviour to survive. The evidence for non-forest habitation is cited as part of the long-standing presumption that such environments were essential to explain key traits during our recent evolution, particularly in regard to our large ‘structurally advanced’ brain and related intelligence. This presumption ignores the much more substantial and extant evidence that large intelligent brains were and still are the product of symbiotic evolution in the relatively benign tropical forests.
There is also the related and equally flawed presumption that finding evidence for some of our ancestors inhabiting non-forest environments accounts for the whole of our ancestral lineage. It’s as if one day all the members of any given ancestral lineage got together in the benign and bio-chemically rich forest and agreed to move en-mass to a much more hostile and bio-chemically impoverished habitat.
Evidence for non-forest habitation by some of our relatives tells us nothing at all of any ongoing forest habitation by others. For example the Olive Baboon can be seen today inhabiting a wide range of environments from semi-arid desert like environments through savannah and woodland to wet tropical forest. Now or in the future, evidence for their existence will be more easily preserved and discovered in arid climates with little chance of finding any evidence for their relative abundance in the wet tropics.
There seems little doubt that individuals and large groups of our ancestors did find themselves in such hostile environments for any number of reasons and using their forest evolved brain and related intelligence survived for significant periods even adapting and speciating. It does seem a bit odd that in the environments that supposedly built and honed our ancestor’s large intelligent brain did not prove to be such a great place to survive. A number of relatively large brained apes still inhabit the forests, yet only one of the many examples found in non-forest habitats still survives and even in its current guise it can still inhabit the forest.
So as the continued evolution and function of our advanced neural system was entirely dependent on a highly specialised symbiotic relationship with plant developmental environments (fruit) any breakdown in that relationship would result in the stall in expansion and erosion of advanced neural architecture. Adaptation would be possible but at the expense of the continued evolution of those highly unique symbiotic traits. Even switching to a greater % leaves and surviving arboreally in the seasonal tropics let alone surviving by hunting and fire use on the savannah would result in regression. The advanced traits emerged and depended on continued and high % fruit specialisation (only possible in non-seasonal lowland tropics). If this is broken the feedback mechanism will stall regardless of returning to same ecology.
We are upright bipeds no longer arboreal where the fruit is so we must have eaten other foods?
Humans (and many now extinct hominids) are clearly highly efficient bipeds. Bipedal locomotion is an integral part of arboreal locomotion, particularly among the larger forest dwelling apes. The presumption that becoming bipedal was initially or primarily driven by non-forest ecology is without foundation. If as the data and our basic physiology supports we had a symbiotic association with the forest then any traits that developed due that association resulting in a less specialised arboreal physiology would not have evolved seperately from that relationship. The developmental symbiosis was and would have evolved and been supported if a less arboreally specialised seed disseminator was emerging. So plant developmental environments readily available not only in the high canopy but in easier reach (of course gravity can help in both scenarios).
Additionally, there is so much focus on human bipedalism that our very effective arboreal capability is ignored. Take the best gymnastic and free rock climbing abilities, add a more functional neural/motor control management system with exceptional balance, co-ordination strength etc. Oh and lose the not uncommon ‘fear’ of heights, (a little strange for a species with an arboreal heritage) and you still have highly effective arboreal abilities. Add in the capability to compete effectively at lower levels with known large fruit eaters and efficient bipedalism becomes more of an added bonus than a handicap.
Of course if you find yourself outside the forest for whatever reason then efficient bipedalism will give you a survival advantage in the relatively hostile non-forest environments. Coupled with a cognitively advanced brain, survival is more likely but will require adaptation to a diet that cannot support the advanced neural architecture or continued neural expansion.
Doesn’t modern imaging data show the left and right hemisphere work together thus negating the ‘simple’ left right dichotomy?
The neural imaging data that is increasingly cited as evidence to dismiss a simple left right dichotomy re perception and function is based on several presumptions. The major presumption that our neural system works, so how does it work, of course we are all obliged to use our neural system when studying our neural system. In addition it is generally presumed that imaging data showing simultaneous activity in both hemispheres can be interpreted that both are contributing equally or in part at the level of perception and function.
This interpretation contradicts basic perceptual, psychological and functional observation and data from split brain research by the likes of Michael Gazzaniga. Nor does not explain rare and radical changes in ones sense of self/perception that correlate with a shift in hemispheric balance such as the well-documented experience of Jill Bolte Taylor. The well evidenced existence of distinct hemispheric related selves, one that is normal and one that rarely emerges and is not a significant part of our normal sense of self does not accord too well with the interpretation of imaging data.
While both sides may light up it doesn’t follow that both sides equally contribute or even contribute at all at the level of perception. For example attempting to spot complex patterns, both sides will show activity, yet the data appears to demonstrate that only one side has any capacity for such recognition. Being deluded by a simple optical illusion will show activity in both sides, yet only one side appears to be susceptible to such delusion, even though in this case we use singular language e.g. “I didn’t see that!” Its really a bit of an obvious one, we wouldn’t have perceptual dominance if simultaneous activity resulted in anything like equal contribution. Hence the evidence for distinct even mutually hostile ‘selves’ residing or correlating with each hemisphere yet ‘normally’ only one is subjectively or objectively apparent despite lots of simultaneous activity.
Archaically the genetically asymmetric (relatively and perceptually primitive) cerebral hemispheres evolved to work together, co-operation between relatively specialised functions. Then the symbiotically modified developmental/operating environment resulted in the ironing out of distinct functionality as the neo-cortex proliferated resulting in a unified sentient sense of self. Only when this new perceptually advanced layer was exposed to the archaic steroid environment creating two structurally and by definition perceptually distinct self-aware sentient beings did problems emerge. The unified sense of self gave way to reducing co-operation then perceptual dominance that inevitably included some functional dominance.
Even if the forest ecology was at one time integral to our neural development haven’t we since adapted?
Yes our distant ancestors adapted to the progressively entangled symbiotic relationship, some of the adaptations were genetic in the classic adaptive selection sense and some were genetic adaptations/responses to the direct effects consequences of a modified developmental environment. However as the symbiotic relationship developed a number a key traits (advanced neural architecture, accelerating neural expansion, extending developmental windows etc) were the direct result of the modified developmental and operating environment. In other words they were non-adaptive, they emerged due to the powerful hormonal cocktail modifying the way the DNA code was read rather than changes in the code its self. We have and may well continue to adapt to the loss of the symbiotic relationship. However the traits and structures that emerged as a direct effect of the symbiotic relationship and were not genetically encoded will erode as the phenomenal complexity that produced them has gone and our genetic code lacks the complexity to compensate.
If the highly advanced and exceptionally rare neural architecture that resulted in the unique perception and functionality of our neo-cortex was not the result of adaptive selection working on our own genetic code (genome) then no. If these and related traits were in fact the result of a convergence of hormonally unique developmental environments in turn the product of many tens perhaps hundreds of highly complex genomes then no chance whatsoever our single genome could even begin to compensate. No single genome ever has built such a system.
That’s not to say we can not adapt, as a progressively more ‘primitive’ and perceptually archaic species if that is where we want to continue, perhaps in the footsteps of the Neanderthals. In effect we have suffered a severely damaging premature birth yet even while separated from the complex gestation environment that is essential for the development of our neural system we can reconfigure the molecular environment. The configuration has always been in our hands, we can continue to choose shit for brains or the most advanced design ever.
If our brain has been degenerating for around 200k years, won’t it take ages to fix?
No, the most exciting piece of this puzzle is that once the condition is recognized it can be treated with immediate effect and in principle, completely prevented within a generation. The increasing complexity of our neural architecture and its accelerating expansion was primarily due to an increasingly and heavily modified developmental environment. Perhaps not surprisingly, the progressive loss of that developmental modification resulted in the asymmetric erosion of the advanced neural architecture and a general contraction in size.
Repairing and accessing the relics of the advanced neural architecture will bring an immediate improvement in perception cognition and psychology as a prelude to restoring full function.
Restore the developmental environment to the unique biochemical and hormonally active regime that dictated an architecturally advanced and expanding neural system and that is what it will design and build as it is the developmental environment that dictates what the DNA code constructs.
The idea that we as ‘individuals’ can be remotely functional or whole again when we (particularly our neo-cortex) were once an integral part of an interconnected symbiotic organism of unimaginable complexity is absurd.
Now some questions for you!
Supported by the data from orthodox science (echoed in the Arcadian traditions) and virtually unique in the whole of biological evolution, our origins were the result of a merging at the developmental level, 24/7 for millions of years with many species of plant developmental environments (fruit). Would an ever more entangled symbiotic association with hormonally rich, bio-chemically complex plant developmental environments explain the unusual traits regarding human evolution?
What impact would a separation from such an exceptionally unique association, effectively a singular organism, have on our physiology, specifically our genetically asymmetric brain and more generally the way our ‘own’ pre symbiotic transcription environment reads our archaic genetic code?
Just suppose for a minute that our neural system had become progressively retarded due to the loss of a unique and complex cocktail of hormones and neuro-active chemicals. Suppose the retardation was asymmetric, one hemisphere being more affected than the other due to ancient genetic variation being asymmetrically encoded between the cerebral hemispheres. Then suppose the more retarded hemisphere and its associated sense of self assumed perceptual dominance due to erosion of function and an increasing psychology of fear and control. (i.e. if the most recent/advanced part of our brain, our neo-cortex was becoming increasingly retarded, one side more than the other and the most retarded side took charge) What would the range of human experience feel like, how would our experience of life, interaction with each other society and culture look etc?
Alternatively is it remotely plausible we wouldn’t be suffering from severe asymmetric neural retardation and a whole host of hormonally/bio-chemically related symptoms if our origins were symbiotic?
If our neo-cortex emerged as part of an extremely rare symbiotic organism, part plant, part animal, would the concept of ‘endogenous’ or ‘exogenous’ regarding hormonally and neuro-chemically active plant chemistry be seriously flawed?