Humans have the longest childhood of any animal on the planet – a remarkable fact. Since children are very vulnerable in the wild, why would evolution risk such a long childhood?
The reason is that there has been a big payoff – a net adaptive advantage – in giving the brain time, during childhood, to learn a vast number of things, and to become trained to be capable of the additional learning during adulthood that enables a person to adapt to and thrive in his or her environments.
All this learning means that the actual structure of the brain must change over time, in a dynamic unfolding process enabled by mechanisms like these:
- Neuronal pruning from the moment of birth: a kind of natural selection within your own brain in which inactive neurons die (“use it or lose it”)
- Greater excitability of individual neurons due to increases in their activity
- Increased blood flow to active neuronal regions
- Stronger synapses between neurons that are firing
- New synapses – “arborization” – among active neurons, like eager spring growth of twigs and buds stretching toward each other in the great forest of the brain
Interestingly, the part of the brain that takes the longest time to fully develop is the prefrontal cortex, which is centrally involved in the “executive functions” of planning and the regulation of feelings and actions.
Stability and Instability
The brain is continually moving back and forth between stable states followed by disturbance and then reorganization into a new stability. In a sense, stability constitutes a signal (in that it is unlikely, in terms of information theory), while instability is a backdrop of “noise” – though very fertile noise, indeed.
These rhythms of stability and instability occur both over long time scales – such as the years of adolescence – and very quickly, such as dozens, perhaps even hundreds of times a second. Stability is needed to have any kind of place to operate from in the world, and instability is needed to have any kind of learning or adaptation.
Within your brain, large numbers of ad hoc neural assemblies – whose individual neuronal members keep changing – are continually pulsing. Each pulse is a momentarily stable waveform which rapidly decays and disintegrates – an illustration of impermanence, one of the three fundamental characteristics of existence identified by the Buddha.
Then there is a kind of fertile instability, an instant of spacious neurological possibility, out of which the next pulse of stable order comes. That spaciousness is a kind of emptiness akin to the absolute nature posited in Tibetan Buddhism within which the universe eternally flickers into and out of existence. In sum, because of the multiplicity and speed of neural assemblies, there are many, many pulses of functional emptiness every second in your brain.
Specialization and Teamwork
The brain works through an exquisite combination of specialization and teamwork. On the one hand, different parts of the brain do specialized things. For example, one part handles producing meaningful speech while another part is in charge of comprehending it. Similarly, there’s a dedicated system for processing faces.
But on the other hand, those various parts work intimately together. Connectivity is the hallmark of the brain, and interestingly, a busy network system is more responsive to individual messages getting through: Paradoxically, noise in a network fosters clear signals! As Robert Heinlein said, “Specialization is for insects.”
This property of teamwork means that information such as memories is often widely distributed throughout the brain, not in one place. And under many conditions, one part can gradually take over the function of another if it’s damaged, an example of what is called “neuroplasticity.”
Further, the self itself is not localized to any single region of the brain. In the image just below (from Gillihan, et al., Psychological Bulletin, January, 2005), each one of the little squares, plusses, and crosses represents a different part of the brain activating during different self-oriented activities (e.g., recognizing oneself in a picture, deciding what one wants).
Self is spread out in the brain, which means that damage to a part of the brain can affect the sense of self, but usually only to a partial degree. And it means that if you quite the sense of self through not identifying with things or taking them so personally, you tend to quiet the brain overall – which is useful during meditation and sometimes other activities.
Each brain is unique, for many reasons.
First, there is genetically-based variation in the quantity and sensitivity of receptors in the brain for dopamine, serotonin, norepinephrine, and probably other important neurotransmitters.
Second, new research is revealing subtle but important differences in certain aspects of male and female brains.
Third, the synaptic connections that correspond to something as simple as the number one differ in a thousand tiny ways in the brains of different people.
Fourth, whatever our genetic endowment might have been, events in utero and from the moment of birth to this present instant have all influenced your brain.
All this calls for respect for individual differences. And for compassion for ourselves and others. As it is traditionally said, there are four types of practitioners: those for whom practice is easy and quick, for whom practice is hard and quick, for whom practice is easy and long, and for whom practice is hard and long.
Whichever group you belong to, what matters most is to practice wherever you are and feed the causes that will lead you to a good result.
And one of the most effective, most fruitful causes to support is the care and feeding of your own brain!
Natural State of Your Brain
When you are fed, unthreatened, pain-free, and not upset, your brain is characterized by being awake and alert, with activation of the parasympathetic nervous system (discussed a few minutes ago), surges of pleasant hormones and neurotransmitters, receptivity to relationship, and a large-scale integration or coherence of billions of neurons firing together in resonant harmony.
In short, the baseline condition of your brain is aware, even-keeled, contented, benign, and integrated.
It’s remarkable that this is the resting state of an organ that’s been finely honed by 650 million years of evolution of multi-celled creatures in an environment in which life typically was, as Hobbes put it, “nasty, brutish, and short.”
This is your home base. It may have been disturbed by an injury or a chemical imbalance or a degenerative conditions. But wherever you go – deep, deep down where your essential nature arises, you are always already home. Or to draw on the quote from J.R.R. Tolkein just below, no matter how dark it gets, there is always light shining through:
Exhausted, crawling with Frodo up the slopes of Mount Doom in the center of the gloom of Mordor, Sam sees “peeping among the cloud-wrack . . . a white star twinkle for a while. The beauty of it smote his heart, as he looked up out of the forsaken land, and hope returned to him. For like a shaft, clear and cold, the thought pierced him that in the end the Shadow was only a small and passing thing: there was light and high beauty for ever beyond its reach.”
Or, to quote Ajahn Sumedho:
Be wisdom itself,
rather than a person who isn’t wise
trying to become wise.
Trust in awareness, in being awake,
rather than in transient and unstable conditions.
This is Part Two of a two-part series
Part One: “How Wonderful is Your Wonderful Brain”