What Is . . .

Excerpts from What Is… Time: Ensconced as we are in our atmospheric cocoon here on Earth, we tend not to think of ourselves as space travelers. But we surely are. We’re moving (on the equator) about 1000 mph through space as Earth rotates on its axis once every 24 hours; and the Earth, as part of the solar system, revolves around the sun at 67,000 mph every 365 days; and the entire solar system, as part of the Milky Way galaxy, revolves every 230 million years around the center of the galaxy—which is about 27,000 light years away—at 483,000 mph; and the Milky Way moves through the universe at 515,000 mph as part of a Local Group galaxy cluster including the Andromeda galaxy, with which the Milky Way, some say, may one day—billions of years from now—collide. And, don’t forget the universe is, itself, expanding. Our speed in the cosmos is altogether an astounding 1.3 million mph, and it seems like we’re not even moving. We also, probably, don’t think of the fact that all the particle physics going on in space (dark energy, dark matter, Higgs field, spacetime warping due to gravity, neutrinos, cosmic rays, etc), Earth passes through and is immersed in it all, as are we. Physics is the same throughout the universe remember. And, time is integral to nearly everything. Life: Life is exceedingly choosy regarding its chemical building blocks. Of countless millions of small organic molecules available, cells typically employ just a few hundred different ones. Most of those came to earth from meteors deposited in the first half billion years of the Earth’s formation. Life only uses left-handed amino acids and right-handed sugars. Then there are self-assembling/self-replicating things going on favoring life’s emergence: cell membranes, reverse citric acid cycle, RNA replicase, and certain genetic polymers. These characteristic all favored the eventual emergence of life. Life, with its five bases and 20 amino acids, is not that complicated. The emergence of life required a reliable, moderate energy source (heat, sun’s rays, chemical). Too much energy (UV radiation, lightning, high heat) was undesirable. Consciousness: The mind, with its massively complex, interconnected, continuously changing biological network of billions of neurons and trillions of connections, is an emergent property of the brain where the whole is greater than the sum of its parts. Our mind does the heavy lifting of thinking, behaving, believing, remembering, and imagining. In a sense, the human brain makes up for its deficiency in sensing reality by amplifying the picture’s brightness, contrast and resolution, so to speak. In what we can call intrinsic sensory augmentation (ISA), some of what our senses miss is filled in by the brain, thus giving us the impression we’re not missing anything. Our consciousness, then, is a product of evolutionary adaptation built up over millions, perhaps billions of years if we allow that human development is an extension of the evolution that preceded us. Add to that qualia—our individual experiences and memories—and the end result is a personal, subjective experience we call consciousness, the brain’s maximal state of awareness, sans drugs. Memory: Memory in the human brain is a dynamic system that stores and retrieves learned information. How does the brain store our experiences and learned information? How can a nerve cell store data for an instant, much less for years at a time? The answer: synaptic plasticity, long term potentiation (LTP) and neuronal circuits. Understanding synaptic plasticity, LTP and neuronal circuits is the main objective of this chapter. The brain has about 100 billion neurons each having about 1000 connections to other neurons. That means 100 trillion possible pathways from one place to another in the brain. Together the vast network of neurons that is the human brain is called the connectome. It is the physical structure of the inner workings of the brain—its wiring diagram. A neuron can be as narrow as one ten-thousandth of a millimeter in diameter yet might traverse from one side of the brain to the other. Still, a neuron is remarkably robust. It’s amazing that with all the pounding their heads encounter in a lifetime, boxers, football players, even soccer athletes can still function at all with all the jostling their trillions of synapses encounter. The hazard, of course, is chronic traumatic encephalopathy (CTE), which is likely to occur after repeated blunt impact to the head. When you learn something new, a circuit of connections take shape. Then, while you sleep, the medial temporal lobe, which houses the hippocampus, amygdala and surrounding cortices, replays the day’s events, consolidating the important things into long term memory and getting rid of the irrelevant details. Most everyone has heard of the idiom “sleep on it.” Studies have shown that sleeping on a problem sometimes provides new insights to the problem, even solutions, the day after a restful sleep. When you recall a memory, you reactivate the entire neuronal circuit associated with the memory, including those brain regions active in producing the original memory—olfactory, visual, auditory, sensory and motor cortices. In the process of recalling, you are recreating, possibly changing the original pattern and incorporating new information you may have received, like the fact, someone later recalls, that at your graduation you had that fainting episode. This is both the power and weakness of memory and neuronal circuits. It’s fairly easy for you to pollute your memories with later information that is not accurate. Neuronal memory circuits change, can fade over time, even disappear, if not used. This is the use it or lose it principle. For the most part, changes are innocuous. But, when someone else’s life depends on it, as in the case of eyewitness testimony, memory failures can be deadly. Our memory is not infallible.