“Nothing in biology makes sense except in the light of evolution.” The Russian-American biologist Theodosius Dobzhansky wrote in 1967. A statement that almost successfully curbs the intricacies of the ontogeny of the nervous system, specifically the brain. This marks the idea that most of biological system can only be understood by zooming ourselves out to the big picture in order to understand the evolution of the brain, wholly. Pressures, competitive or even volatile environment force us to push through, acclimatize and maneuver this demanding situation with a set of skill, mental toolkits and knowledge. Yet, we can ascertain, towards the future, the novelty still often leaves us with perpetual questions, cornered us perplexed at the edge of the unknown. Hazy uncertainty is dancing everywhere in our head. Hence, the usual suspect, anxiety ensues. And as we’re trapped in this echo chamber as the given pressures are enhanced strongly, there is a particular part in our brain being summoned – to respond, the prefrontal cortex. Driven by gene-environment conflicting interplay to seize contingencies, account for their risks and benefits as one goes along, adopt which fits, and proceed to adapt in real time. That, however, an oversimplification of taking the prefrontal cortex into account. As the Dutch biologist Niko Tinbergen suggests, in order to swim into the depth of any biological system, four questions we should ask beforehand as a general rule: how did it evolve (phylogeny)?; how does it promote fitness (selection)?; how does it develop (ontogeny)?; and how does it work (mechanism)? Understanding a system that is hierarchically complex and multifaceted like the central nervous system – the answers to the last two questions would not get us anywhere the core of prefrontal cortex since they only concern about the how as opposed to the first two questions about why the how is. Thus, an evolutionary framework needs to be employed, as a means to an end.
Primitive design: automatic nervous system as the precursor of evolution
Back around 1932, known as the father of neurology thanks to his seminal contribution to the matter of epilepsy, John Hughlings Jackson, has made an attempt to get around the confusion surround the nervous system, in Evolution and Dissolution of the Nervous System. By means of Darwinian logic, he echoed and deployed the Spencerian evolutionary framework. It is suggested that long prior to the modern anthropoid, the nerves primitively mechanized the evolutionary road from the most simple to the most complex – which, Spencer argued, regression, evolution, heterogeneity, complexity and progress are the frictions from which natural selection mobilizes onwards:
If the doctrine of evolution is true, the inevitable implication is that mind can be understood only by observing how the mind is evolved.
And:
The progress from a state of indefinite, incoherent homogeneity to a state of definite, coherent heterogeneity.
Early on, our nerve centers are at first poorly organized, and the information processing is arduously required to be structured as evolved. This Darwinian framework is akin to foraging model in the ancestral times. By purpose of fulfilling a basic biological pressure to survive, suppose a forager hunts for food out in the wilderness. The catch is, it gives room for predators to get in the forager’s way at a given time and place. This inevitable danger certainly will put him at risk that may result his body in switching to defense mode, when necessary. The sympathetic nervous system as often is associated with fight-or-flight mode that takes form of fear, once an air of danger is detected to the point of a real danger, is going to immediately secrete hormones associated with stress from adrenal glands and release energy by ramping up one’s heart rate, blood pressure, sweat glands, lowering saliva and the activity of digestive system – as for preparatory counterattack rushing straight from automatic system to the motor system, and eventually some physical altercation proceeds. This basic survival mode involves hand-eye coordination, only. And given how involuntary, directed and immediate with no conscious thinking required during which time the sensory-signal input altered to motor-enactment output is, Jackson thus associated this most simple with automatism. From this scenario alone, we can infer that the nervous system in the prehistoric period evolved to ‘react’ immediately against threat, hence individuals back in those days have stronger propensity for reflexive and reactive behaviors. They are almost always wired to fight to the point of becoming an autopilot, considering the volatility of their environment predisposes them to be 24/7 alert, if not programmed by evolution as such.
The Dawn of Consciousness: Order amid Chaos
Still, bear in mind, the frontal cortex is responsible for selecting, filtering, inhibiting sensory stimuli from automatic nervous system. And for all those obvious reasons, they are the antithesis of automatism. For more than a thousand years tilting further away from the savagery of Stone Age to today we step in at the age where artificial consciousness starts tinkering. It is not unreasonable to ascertain that homo sapiens has incrementally yet painstakingly ascended from low- to higher-leveled hierarchy of the brain. And because the junction between stages is so imperfect and complex, Jackson argued, this transition zone being a spaces between order and disorder leads to how natural selection plays its own part. Adaptation processing in the face of disorienting chaos ensues. This adaptive system can be thought of when bottom-up meets top-down. So in the foraging example, that incipient threatening signal detected by the sympathetic nervous system in the form of sensory stimulus leading to motor reaction i.e., physical altercation is when bottom-up stage takes place. It compels an agent to react in real time as a result. But now and then, considering the misfortune of such unwanted events, more so having experienced this degree of danger in this particular territory, would the forager risk his life twice by the same level of jeopardy on the next round? Of course, something needs to change. The word ‘change’ is central for the transition from bottom-up to top-down. The forager, given the circumstances, may start reconsidering the choice of the hunting area, or the kind of weapon he could and should have equipped himself with as to keep the predators at bay, or perhaps the timing issues. This degree of abstraction involves learning and memory.
Chaos, in the sense of disorderliness that entails event and uncertainty surrounding the pre-event, bolsters the brain to integrate and coordinate which best action should it be generated as to preemptively anticipate the best and worst outcome. For this reason, chaos can also be thought of as the catalyst for order, which the frontal cortex has gradually and imperfectly long evolved to reconcile the past and the future. It is the episodic memories of the past event that have been stored, whose information is retrieved for assessing risks-and-benefits before the possible and probable outcomes being predicted for the upcoming scenario (the future). That feedback-loop processing also known as top-down modulation, which inextricably is dependent on and influenced by what causes it. Not only by principle, is it argued by evolutionary biologists to be the source of many philosophical problems, causation, also often argued to be preceding the effects. As the name suggest by the very theoretical conceptualization, especially in the context of biological system, which stated as following:
All processes at the lower levels of a hierarchy are restrained by and act in conformity to the laws of the higher levels.
Mitchell Waldrop, in Complexity: The Emerging Science at the Edge of Order and Chaos (1992), said it more poetically:
Right between the two extremes... at a kind of abstract phase transition called the edge of chaos, you also find complexity: a class of behaviors in which the components of the system never quite lock into place, yet never dissolve into turbulence, either. These are the systems that are both stable enough to store information, and yet evanescent enough to transmit it. These are systems that can be organized to perform complex computations, to react to the world, to be spontaneous, adaptive, and alive.
So as we know from evolutionary perspectives, an adaptation is a trait that has been modified by natural selection over evolutionary time for the function of the trait. The quality of error-reductions and the speed of informational processing streaming from lower to higher level hierarchy, as alluded, has so much bearing on how strategically agile and shrewd an agent responds to frictions at the brink of chaos.
High-Ordered Control: Executive Function and Hierarchical Representation
It now becomes more reasonable to ascertain this painstaking journey towards the seat of consciousness – moving from lower, organized, homogenous, coherent, simple upwards to higher, unorganized, heterogeneous, complex neural mechanism. A steep and prolonged ladder with sequences of friction where each step gives a room for natural selection. This is when incoming stimuli and automatic flow over time hindered by the skepticism of feedback-loop records laid on the table. The more complex is the task for the frontal cortex to integrate and coordinate the excitatory rush coming from automatic lower nervous system into the inhibitory brakes located in the higher strata of the cerebral, the more advanced is the representation the cognitive function must tackle. Jackson (1932) thus encapsulates Spencerian mind evolution as following:
Evolution is a passage from the most to the least organized. “Highly organised” is frequently used synonymously with ‘very complex’: but by degrees of organisation I mean degrees of perfection of union and certainty of action of nervous elements with one another. Using the term organised in this sense I say that the highest cerebral centres are the least organised (the “most helpless centres”), although they are the most complex, whereas the lowest centres are the most organized, although the least complex. In other words, we may say that the evolutionary ascent is from the least to the most modifiable. If the highest centres were not modifiable, we should be very simple machines; we should make no new acquirements. If the lowest (“vital”) centres were to become modifiable as the highest are, life would cease.
“Higher centres” means to encapsulate the so-called executive function. The advanced, sophisticated, and most conscious of the human mind, where it takes place in the sub-regions of, including but not limited to, all the hubs that are tightly connected with the prefrontal cortex. For most of executive functioning ability involves working memory, decision-making, problem solving, adaptive functioning, suggestibility, planning, managing goal-directed behaviors and actions. There are two ranks of hierarchy divided: the empathy center and the rational center. Empathy, in the context of theory of mind, is measured by the ability to attune, micromanage, infer a wide range of affect, externally or internally, thus as the name suggests ‘emotional executive function.’ Rationality, on the other hand, by the capacity of getting around complex problems, inferring logic and detached reasoning, generating many short-term contingency plans within a scheme of long-term planning - which, lies even higher in the hierarchical system than does the emotional. Hence, ‘meta-cognitive executive function.’ Functionally, however, both are not mutually exclusive. Relative to the individual’s preference or genetic predisposition toward how to approach life, in order to govern optimally and make the rulings adaptive and appropriate, the prefrontal cortex couldn’t have done these weighing pros and cons without its connectivity with milieus rooted from beyond.
Admittedly, although cognition and emotion can be intertwined and involved inseparably especially when an important decision-making has to be made under fire, it requires more hierarchically complex thus is extremely rare to get that balance stroke. To simplify, caudal areas (bottom), such as the limbic system, responsible for emotions, motivation, long-term memory; the cerebellum, for movement and motor-related coordination; while the non-caudal orbitofrontal cortex, for visceral sentiments in the form of olfactory, gustatory, somatosensory, and visual perceptions. As mentioned, the relationship in between is tightly reciprocal that their way of interacting can be described as communicating feedbacks constantly from lower to higher and back to lower order. Since many of the frontal’s job also involves repeating neural representation systemized in a hierarchical order, thereby top-down ruling essentially is about selecting and filtering, if not suppressing, whatever internal and external influences that are not admissibly relevant to the means of a goal, since it can interfere the best-predicted outcome. By means of hierarchical representation, this whole system and mechanism, evolutionary and ontogenically, is also about one moving from primary sensory to higher order areas, reaching for the most complex pattern in the prefrontal cortex. As John Hughlings Jackson, never tired of saying: it is a profound mistake to take the brain to be a ‘solid mind.’
To understand the logic of neural representation, hierarchy, and which brain connectivity or region involved in, imagine this following thought experiment:
A group of Nazis hunts the Jews in one specific territory. There is a possibility of hiding Jews in that territory, thus resulting soldiers to proceed an enhanced operation by cleaning up the areas. They broke down every hut and house where the usual suspects are suspected to be inside. As they wander around, a sound of crying baby caught to their ears. The mother of the baby is apparently not alone with the baby per se. She is with company, having five people with her including friends, neighbors, and relatives, hiding discreetly underneath the wooden floor of a hut. She caught between a rock and a hard place as to how resolve such a dilemma.
She has two options:
1. Saving five people → at the expense of the baby → killed by the Nazis — less likely.
2. Keeping one baby → at the expense of the five Jews (including the mother and possibly the baby) → killed by the Nazis — more likely.
As philosophically conflicting as it became notoriously widely-debated, this dilemma has indeed attracted the attention of researchers and scientists to investigate the neurobiological underpinnings of each option chosen. Neuroimaging evidence shows, there is a strong activation in the amygdala, insula, anterior cingulate cortex (ACC), the orbitofrontal cortex (OFC), which also sometimes called ventromedial cortex (vmPFC), of those who go with number two. As the ethics’ model suggests, it is hypothesized that due to the underlying emotion contributes predominantly to how they make a decision. But even when we page through back to their anatomy, it is sensibly consistent. As we have learned, the amygdala is responsible for detecting danger, this somatic marker in the form of fear then activates the so-called amygdala’s brake, anterior cingulate cortex (ACC) to reflect the feeling of sadness, anger, guilt, etc before rostrally going upward to the prefrontal cortex, specifically a part weighing the outcome of that emotion, the ventromedial prefrontal cortex (vmPFC). The temporal sound of the crying, the vulnerable and helpless look that the baby painfully transmits to the viscerally-responsive OFC enough to evoke a sense of guilt thus dissuade the morally-constrained vmPFC from smothering the baby. When the decision of not killing the baby is made despite the long-term outcome to the contrary, neuroimaging shows, this neural representation reaches only as high as the second order hierarchy. Hence, a re-representation of representations. They trade the lives of the collectives for the guilt they dreadfully may have to bear in the future, as the outcome, if opting for the death of a baby. Hence, the rationalization of option 2 may sound like, “Any living individual can never be a pawn.” They are less likely smother the baby irrespective of the costs of doing or not doing it because their emotion has overpowered the cognition can they otherwise opt with.
Contrary to those who go with the option 2, option 1, a stronger activation takes place in the most rational and unsentimental part of the PFC: the dorsolateral prefrontal cortex (dlPFC), who might respond to the decision made by the vmPFC, “Well yes, for the right outcome.” The dlPFC will be more than happy to disregard emotions for maximizing benefits to and acting upon the interest of the many as opposed to of the few [19]. This level of impersonality and disinterestedness makes the dorsal areas of the PFC sit at one level higher above the vmPFC (or OFC), insula, ACC, amygdala, hippocampus, including the rest of nerves associated with automatism. It is when the second level representation projecting feedback from the lower order is modified to become a re-representation of the re-representation. As the neurobiologist Robert Sapolsky in Behave viewed dlPFC as, ‘a decider of deciders,’ to the point of, as the neuroscientist Joshua Greene also profiled this particular brain area, ‘a hallmark of human cognition’. Weighing the pros and cons in the way of not only how people direct their own action but also what they are as a “human being” has been a longstanding battle between the vmPFC and the dlPFC in deciding that which whether driven by the rule of principle or by of consequence. In addition, dlPFC is also believed to be the part of the brain that matures last, and because of this, is the most recent contrary to the limbic system and least constrained by genes. Thus, it does not fully mature until the individual reach the age of 25. For it takes more or less this range for the individual rolling with the punches, and learning reversibly from non-shared environments – be it mentors, teachers, or tutors.
References
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