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The Star Larvae Hypothesis
Nature's Plan for Humankind
Part 3. Space Brains

Neuroplasticity and the Enrichments of Weightlessness

Bones and muscles—adaptations to gravity—atrophy in space, but brains are poised to bulk up.

The deterioration of bone and muscle tissues in weightlessness suggests that a particular morphology, or body type, will characterize the extraterrestrial descendants of humans.

Similarly, the enriching effects of weightlessness on brain tissue, described below, suggest that native extraterrestrials will enjoy a particular, and peculiar, consciousness. Because weightlessness allows bodies to move and orient themselves in ways that they cannot on Earth, it will promote robust brain development.

In What's Going on in There? : How the Brain and Mind Develop in the First Five Years of Life, neurobiologist Lise Eliot describes the foundational importance of the vestibular sense in the overall somatosensory and cognitive development of infants, i.e., in their brain development. The vestibular sense has to do with bodily orientation (e.g., upright, inverted, prone) and motion in space (e.g., rocking, falling, spinning). The vestibular sense is mediated by the vestibular organs of the inner ear in conjunction with proprioceptive input from limbs and torso.

On Earth, the tug of gravity conditions the vestibular sense, from birth. But in weightlessness, the vestibular sense will be conditioned by a different set of influences, namely by a body's freedom to move in three dimensions without constraint. Minus gravity, newborns won't be forced to spend time helplessly supine, as they are on Earth. But floating, gravityless, they will be able on their own to generate vestibular experiences of all kinds, moving and reorienting their bodies as much as they care to.

Eliot describes a series of low-tech, low-budget experiments in which infants from 3 to 13 months old simply were held by researchers in swivel chairs and spun in one direction then the other with their heads tilted in various ways. The infants received this treatment four times a week for four weeks. A control group received no such treatment, and a second control group sat on the researchers' laps but did not spin. Eliot notes,

"The results were striking. Compared with both control groups, the babies who were spun showed more advanced development of both their reflexes and their motor skills. [. . . . ] Vestibular stimulation appears to be equally beneficial to very young infants. Newborns cry less when they are rocked, carried, jiggled or suddenly changed in position, all actions that activate the vestibular system. [. . . .] Indeed, infants who are comforted through vestibular stimulation show greater visual alertness than babies comforted in other ways. It's during these periods of quiet alertness that babies do their best learning, when they can most effectively absorb information about the world around them. [. . . . ] As one of a baby's most mature senses, the vestibular system provides a fast track into her developing brain. It doesn't take long for most parents to discover the power of this hidden sense, but isn't it nice to know that all that rocking, jiggling and carrying is not only soothing to your baby, it is actually quite good for her emerging mind?"

In weightless space, infants won't need spinning chairs to enjoy varieties of vestibular experience. Through their own efforts, They will be able to generate all the vestibular stimulation that they will be able to tolerate. Given this prospect, living in weightless space will entail dramatic neuro-developmental and neuro-evolutionary outcomes built upon neural enrichment.

This is a good example of an experiment which was low cost but still successful. Funding for scientific experiments can be difficult to come by, so anyone with knowledge about the newest accounting certifications online would be impressed with the outcome of this simple low-budget experiment.

Brain Development: An Overview

The changes that weightlessness will produce in brains will be due not necessarily to changes in gene behavior (though it seems likely that that will be a factor. See tintblock at end of this page) but to the peculiar way in which brains develop in relation to their environments. The cells that compose most tissues reproduce and thereby replenish the cellular population in those tissues, as old cells die. Unlike most other cells, however, brain cells, or neurons, don’t reproduce (though brain tissue can be partially replenished, as described near the end of this page). Like other cells, neurons do die. And yet, with its neuronal population shrinking as cells die, a human brain grows dramatically in weight and volume during its early years. A brain grows quickly in utero as new brain cells develop. Once its bearer is born, a brain grows by creating more connections—synapses—among its cells. The density of synapses in brain tissue peaks in humans between the ages of three and six, then tapers off, by about 50 percent, to adult levels by late adolescence. A typical human brain reaches 95 percent of its adult volume by the age of five.

Overview: a brain cell comprises three main components:

• The axon is a branching stem that reaches out to and establishes contact with other neurons.
• Dendrites are fibers that receive incoming signals from other neurons.
• Synapses are the junctions at which dendrites and axons meet and through which neurons exchange their chemical signals.

A young brain overproduces synapses, then selectively prunes the excess. A New York Times review of brain research (6/24/86) tapped an artistic metaphor to describe the process: "Nature is like a sculptor using two methods. The sculptor first builds a framework and progressively adds plaster to it, producing a rough shape that approximates what he wants. Then he chips away at it until the definitive form appears." No doubt future research will clarify the details of the process, but the general pattern of an overproduction of synapses early in childhood followed by a pruning of underused ones is well documented.

The synapses that survive the "chipping" to compose the "definitive form" of the adult brain represent neurological pathways selected and maintained by the environment. How environments select the synapses that survive has been studied extensively through a simple methodology. Since the 1970s researchers have been comparing brains from subjects—rats—that are raised in experimental environments with the brains of rats raised in control environments. In the classic experiment of this type, some rats lead a privileged life, growing up in a spacious cage filled with toys and littermates. Researchers typically call this the enriched environment condition. The control subjects endure lives of privation, growing up in solitary confinement in barren, cramped cages. This is the impoverished environment condition. When the brains of adult rats from the two environments are compared, those that develop in the enriched condition weigh significantly more than those that develop in the impoverished condition. The weight difference is due to a difference in synaptic density. Researcher William T. Greenough, generalizes from these findings: "[The] results suggest the number of synapses per neuron in a variety of brain regions is determined to a significant extent by the circumstances under which the organism develops. We speculate that these changes are involved in storing information arising from experience." (quoted in Richard Restak's The infant Mind.)

Greenough's speculation is general enough to raise questions: Does a particular type of experience disproportionately influence synaptic retention? Or, is intensity itself the determining factor? That is, what specific characteristics of environments account generally for their ability to enrich or impoverish brains?

Move It Or Lose It—Neuroplasticity And Environmental Enrichment Effects

A typical response to this line of questioning comes from neurologist Marian Cleeves Diamond. She is straightforward about operationalizing enrichment: "In essence, an enriched environment is one which introduces more stimulation to the body’s surface receptors than does an impoverished one, whether it be for rats or human beings." This explanation, from Diamond’s review of developmental neurology, Enriching Heredity, typifies the conclusions of scientists working in this field, because it gives primacy to sensory input.

But sensory input is only half the story. Motor activity—muscle output—plays at least as great a role in producing enrichment effects as does sensory input.

And this under-appreciated fact underlies a central contention of the star larvae hypothesis: Brains will develop with pronounced vigor, becoming superenriched, when they develop in an environment of weightlessness.

This contention is supported by a variant of the standard enriched/impoverished experiment. The variant demonstrates that a developing brain has to move a body if it is to preserve an enriched neural infrastructure. Passively receiving sensory input is not enough. In the variant experiment, "observer" condition rats are raised singly in small cages that are fixed in place inside a large enriched cage. In terms of brain weight, rats free to roam in the enriched cage outperform the confined observers significantly. Researchers who have published the results of such experiments report that, "Although the observer condition rats shared the sights, sounds, and smells of their enriched condition littermates and had some contact with them through their wire-mesh cage walls, the observer condition brain weight measures differed significantly from those of the enriched condition but not from those of impoverished condition rats."

In other words, sharing the sights, sounds, and smells of their free-ranging cohorts does observers no more good than does being subjected to the solitude, isolation, and confinement of impoverished cages. From their results the researchers conclude, "It appears that the necessary and sufficient condition for the production of enrichment effects is active interaction with varied inanimate stimulus objects." (Both quotes are from Ferchmin, P. A.; Bennett, Edward L.; and Rosenzweig, Mark R., “Direct Contact with Enriched Environment is Required to Alter Cerebral Weights in Rats,” Journal of Comparative and Physiological Psychology, Vol. 88, No. 1, pp. 360-367.) Richness of sensory input alone does not ensure generalized neurological enrichment, it turns out. Interaction with the environment—movement, that is, which produces sensory feedback—is required. The vestibular system needs to be tapped.

More evidence: Using a different experimental approach, psychologist Richard Held in the 1960s ran a series of experiments in which he upset the normal correlation between sensory inputs and motor outputs, with telling results. In one case, human subjects practiced strolling a winding path while wearing goggles that distorted their vision. Subjects in a second group wore the goggles while being conveyed down the path in a wheelchair. Those who walked—those who engaged the environment actively and received sensory feedback from their self-initiated movements—subsequently scored higher on tests of visually guided tasks than did those who were conveyed passively. More manipulative experiments with animals produced similar findings. Accounts of Held's canonical work can be found in any general psychology textbook.

Held proposed that the exercise of "sensorimotor feedback loops" in the brains of the active subjects helped produce their higher test scores. An enriching environment’s "richness" seems to be a measure of the complexity and abundance of the sensorimotor feedback loops that the environment exercises. The more complex the input-output feedback relationships that a brain has to manage—the more synapses regularly exercised, it would seem—the more enriched and long-lived will be that brain's synaptic network. The point is that physical output and sensory input both must be present to produce generalized enrichment effects.

But of the two processes, physical activity and sensory input, physical activity should be considered the primary influence on brain development. Our bodily movements continually alter our vestibular and proprioceptive experiences, as well as our sensory experiences, what we see, hear, and touch. For this reason, motor activity, not sensory input per se, should be considered the sine qua non of neurological enrichment. A brain that develops while it receives input passively, or with only a small capacity to respond with movement, will forgo most of its potential for enrichment, as "observer"-condition subjects show.

A newborn floating in weightlessness will enjoy a vastly enriching environment.

A baby held down by gravity endures an impoverishing one.

Watch the space station commander drift and tumble from place to place. Then imagine babies born into this environment, living their lives and growing into adults there. Developing in an omnidirectional world, their brains will be wired fundamentally differently—much more complexly—than those of their terrestrial counterparts. Sensorimotor feedback drives the complexity of neural circuitry, and weightlessness expands the potential complexity of sensorimotor feedback. Weightlessness is an evolutionary trigger, a mutagen that turns hominids into something like angels.

In The Descent of the Child, Elaine Morgan quotes John E. Eisenberg's The Mammalian Radiations, in which Eisenberg compares modes of locomotion among mammals along with their corresponding brain sizes. He summarizes,

"One will note that complex locomotor patterns involving movement in three different directions, such as arboreality or aquatic adaptations, are strongly associated with high encephalisation quotients, whereas movement in essentially two dimensions generally is associated with a lower encephalisation quotient."

Morgan comments,

"This would explain why all primates, being originally arboreal, have slightly bigger brains than most non-primate species. This correlation would lead us to expect that an arboreal primate descending to the two-dimensional world of the savannah would have lesser needs in respect of brain size. But locomotion in water—swimming and diving—is three-dimensional and, other things being equal, it would tend to lead to higher encephalisation."

If such reasoning is sound, then one would expect gymnastic potentials released by weightlessness to correlate with high levels of encephalisation. Native extraterrestrials should bear brains that are hypertrophied, by terrestrial standards, because they will spend their lives moving in three dimensions. (To Morgan's point, these observations similarly throw light on the anomalously enriched brains of cetacea—whales and dolphins—which also navigate in a three-dimensional world. Moreover, recent research has revealed that the brains of those other 3-D navigators—birds—are conspicuously neuron rich. See "Birds Have Primate-Like Numbers of Neurons in the Forebrain", Seweryn Olkowicza, et al., Proceedings of the National Academy of Sciences (PNAS), vol. 113 no. 26, June 28, 2016. See also "Birds Have Skills Previously Described as 'Uniquely Human,'” in The Scientist, December 2016 issue). Defying gravity, by aquatic or aeronautical means (or by abandoning gravity altogether?), seems reliably to correlate with neurological enrichment, with whatever psychological implications that entails.

(WARNING! Digression: The binge-purge strategy characterizes not only the development of brains, but also the evolution of planetary life generally. Episodes of mass speciation have alternated with episodes of mass extinction. During the past several hundred thousand years, cycles of glaciation have intensified evolutionary competition, and the cycles have driven evolution—while preserving Gaia's climatological support systems—toward a pinnacle of planetary adaptedness in the form of Homo sapiens. Humankind spans all climates; we are the most geographically dispersed species on Earth, having adapted to all climates by engineering locally hospitable mini-climates. This is the process of urbanization, and its extensions now include the weightless International Space Station. Glaciation cycles function as genetic filters—stress tests—that drive the Earth's gene pool toward climatological adaptability—an adaptability that ultimately takes the form of humankind’s ability to construct niches that enable it to occupy climates as hostile as that of outer space. A readable book that places this genomic plasticity in the larger context of Earth's ontogeny is Peter Ward and Donald Brownlee, The Life and Death of Planet Earth. See also Gould and Eldredge's theory of Punctuated Equilibrium.)

Neuroplasticity And The Enrichments Of Intrauterine Weightlessness

Evidence from prenatal research corroborates the emphasis on movement as the primary factor in producing enrichment effects. Fetuses cavort in their amniotic capsules like astronauts, and their gyrations apparently pay off neurologically. In The infant Mind, Richard Restak notes that ultrasound imaging reveals two predictable patterns of intrauterine movement:

"In the first movement pattern, the head is flexed backward and turned to one side. This is accompanied by rotation of the trunk and the rest of the body to the same side. In the second movement pattern, leg movements occur, almost as if the fetus were pedaling a stationary bicycle, resulting in a somersault as the legs contact the uterine wall. . . . These movements serve the purpose of stimulating brain development, especially those structures having to do with balance, coordination, and coping with the forces of gravity."

How spinning in three-dimensions in an environment of simulated weightlessness would prepare an organism for the relative flatness of a gravity-bound world is unclear. Newborn brains might be better adapted to a weightless environment, given their prenatal experience. In any case, the womb bears the hallmarks of an enriching environment. It exercises (kinesthetic and tactile, vestibular and proprioceptive) sensorimotor feedback loops.

But once its bearer towels off, a fetal brain's prospects plummet. Birth is a crisis for a developing brain. It demotes the gymnastic fetus to the lowly status of sidelined newborn. No matter how intense its sensory experience, a newborn can’t respond with much movement. No more brain-stimulating gymnastics for the kid in the crib. Infants are essentially beached marine mammals. Outside the watery environment of the womb, they are unable to respond in any gross muscular way to their sensory inputs. They are "observers" in the clinical sense of the rat experiments.

Healthy newborns eventually overcome their immobility by sequentially mastering specialized skills. They squirm and in a few months learn to roll over and crawl. Infants will pull themselves up by clutching onto furniture at ten months or so and take a step somewhere around their first birthday. They go on to walk, run, climb, jump, pedal bicycles, and in other ways establish working relationships with gravity.

This programmed sequence segues later in life into rote habits of adulthood. In its mature state in a workplace, a typical middle-class American brain will spend much less time moving in complex ways than it did on the playground in its formative youth. It may be subjected to long hours immobilized at a desk engaging a computer through keystrokes and mouse clicks, in a bucket seat engaging a drivetrain through slight arm and foot movements, and reclining in an overstuffed chair engaging TV fare through buttons on a remote control.

The paralysis of the newborn, the skills acquired in sequence during childhood, and the relative sloth of adulthood collectively must engage and maintain a relatively meager set of sensorimotor feedback loops. Synapse-rich toddlers become brain-damaged adults as they schlep into their senior years the few synapses that survive "the trimming of exuberant collaterals," as some researchers have labeled the synaptic selection process. And in this relatively impoverished state modern urbanites function normally, for the most part, being by adulthood well adapted to the vestibular and proprioceptive impoverishments of terrestrial urbanity.

In contrast to the strictures just described, an enriching curriculum awaits brains that develop in weightlessness. Not having to spend their first postnatal months beached on the gravitational shore and instead enjoying the freedom to fly, is a prospect that a brain’s "exuberant collaterals" could only welcome.

Bodily Movement Replenishes the Neuronal Population

Moreover, the neural enrichment that weightlessness promises stands to be augmented by the addition of new neurons throughout life. In contrast to the traditional view that no new neurons form after birth, research conducted in the 1990s revealed that brains develop new cells throughout their lives and that bodily movement stimulates the development of these cells. Space brains might become pumped up not only in terms of synaptic density per neuron, but also in terms of the sheer numbers of neurons that they possess.

New cells in adult brains don't arise from the same process as do most other cells in a body, which arise when a mature cell divides into two cells. The brain cells that arise after birth develop instead from layers of immature stem cells that are retained deep in the brain from its embryonic days. The cells mature as they migrate out of the immature layers.

The new research is summarized by neurobiologists Gerd Kempermann and Fred H. Gage in the May 1999 Scientific American. The authors conducted their own enriched/impoverished experiments using a variation of the standard methodology. Two groups of mice were raised in standard cages, one with running wheels and one without. "The mice having unlimited access to the wheels made heavy use of the opportunity and ended up with twice as many new nerve cells as their sedentary counterparts did, a figure comparable to that found in mice placed in an enriched environment," the researchers report, confirming the preeminence of bodily exercise in promoting enrichment effects.

The cover story of the March 26, 2007, Newsweek goes further and reports on the link between exercise and brain growth in human subjects.

"After working out for three months, all the subjects appeared to sprout new neurons; those who gained the most in cardiovascular fitness also grew the most nerve cells. [. . . .] So far, though, for reasons no one really understands, the few studies that have examined stretching, toning, and weight lifting have found little to no effect on cognition."

This observation underscores the connection between complexity of sensorimotor feedback (cardiovascular exercise vs stretching, toning and lifting) and enrichment effects.

Research that Gage and colleagues continue to conduct in this field keep turning up results that support the contention that varieties of bodily movement promote neurological enrichment and thereby, by implication, that weightlessness is a neurologically enriching environment, because it promotes the greatest variety of bodily movements. A feature article in the October 2015 issue of The Scientist magazine (“Brain Gain”, by Jef Akst), summarizes the ongoing work:

“What we found was that there was surprisingly much neurogenesis in adult humans,” [Jose] Frisén says—a level comparable to that of a middle-aged mouse, the species in which the vast majority of adult neurogenesis research is done. “There is hippocampal neurogenesis throughout life in humans.”

As the article later acknowledges, “Epidemiological studies have shown that people who lead an active life—known from animal models to increase neurogenesis—are at a reduced risk of developing dementia, and several studies have found reduced hippocampal neurogenesis in mouse models of Alzheimer’s.”

The theme of exercise merges into that of youthfulness, or juvenilization: “For a period of about four or five weeks, while [the newborn neurons] are maturing, they’re hyperexcitable,” says researcher Gage. “They’ll fire at anything, because they’re young, they’re uninhibited, and they’re integrating into the circuit.”

The story of life. But the characterization grabs the attention of the star larvae hypothesis, because it supports the hypothesis’ contention that bodily movement drives neurological enrichment and that, therefore, weightlessness is the ultimate neurological enricher.

So, what’s an enriched brain supposed to do with all that extra gray matter? The Newsweek article suggests the direction in which enrichment carries a brain: "[T]he hippocampus is especially responsive to BDNF's effects, and exercise seems to restore it to a healthier, 'younger' state. 'It's not just a matter of slowing down the aging process,' says Arthur Kramer, a psychologist at the University of Illinois. 'It's a matter of reversing it.'" (BDNF is brain-derived neurotrophic factor, a brain chemical described in the article as "Miracle-Gro for the brain".)

Weightless, enriched, neurology would seem to aim its corresponding subjectivity—the qualities of experience that it mediates—at youthfulness, at juvenilization.

NEXT > Neuroplasticity and Neurological Neoteny

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