Neuroscientists and psychologists have been interested in the Earth-brain relationship for some time and have devised means of studying it. As I’ve pointed out, microenvironments can select different traits in the same species (think Galapagos turtles and finches). Therefore, not all members of a species experience the same Earth.
The renowned Donald Hebb was famous for his ideas on how learning is captured by changes in communication between nerve cells. He also had an interest in how exposure to different environments (so-called environmental-enrichment manipulations) influences general intelligence. In a well-known study, Hebb allowed one group of rats to grow up in impoverished conditions with little stimulation and compared them to another group that he, much to his wife’s dismay, brought home for sensory stimulation. He found that the enriched rats performed better on a variety of learning and memory tasks and that they also showed more elaborate brain architecture in the form of synaptic connections. A more complex world can help produce a more efficient and equipped brain.
This principle is captured nicely by the processes of neural Darwinism and synaptic pruning, which tailor the developing nervous system to the specific demands of the immediate microenvironment. For instance, visual sensation and perception depend on connections between cells in the retina (which is considered to be an extension of the central nervous system) and the lateral geniculate nucleus (LGN) of the thalamus. Some of the connections between these regions become efficient during early development, while other projections and connections are eliminated. This occurs in line with a sort of “Use it or lose it” rule. For example, in people with a lazy eye, this experience-based reorganization does not occur effectively. This is due to muscular impairment preventing the eye from being properly directed at visual stimuli and, therefore, insufficiently stimulated by experience. The lazy eye is found to have scattered and inefficient connectivity to the LGN.
This is similar to what was seen in some old, ethically dubious studies conducted by perceptual psychologists and physiologists. In monocular-deprivation studies, a newborn animal subject has one eyelid sewn shut to prevent that eye from receiving visual stimuli during what is now referred to as a “sensitive period.” During the sensitive period, neural Darwinism and synaptic pruning shape the brain based on experience and interactions with the physical world. The subject’s deprived eye shows similar perceptual and anatomical deficits as the lazy eye in human subjects compared to healthy and nondeprived eyes.
Life experiences can be preserved in the genetic code of a species to help future generations deal with species-specific threats. Researchers have shown that members of subgroups in the same species show innate defensive behaviors when presented with the apex predator from their own microenvironment but not with another subgroup’s predator, and vice versa. For example, humans appear to have innate revulsions to snakes and some insects that do not appear to entirely depend on social factors. Some people like to think about these innate releasing mechanisms as sort of Jungian archetypes.
Other nonhuman animals show innate responses to similar threats, and, even further, other animals have evolved to take advantage of these reactions. Some moths have evolved patterns on their wings that resemble an owl’s face. This provides an excellent defense mechanism against predators that possess their own class of defense mechanisms, such as fleeing at the first glimpse of anything that looks like an owl. Score one for the moth.
Given the variety of survival demands for life on Earth, it is no wonder that the brain has been perfectly molded to navigate though these microenvironments, even within a species. The ability of these brain-shaping experiences to be preserved in genetics and passed down for further tailoring based on the next generation’s experiences provides the groundwork for future specialization. Hopefully, this will take the form of immunities to hostile diseases and enhanced cognitive abilities due to our changing societies rather than comically exaggerated appendages.
This article was first published in Brain World Magazine’s Summer 2014 issue.
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- Your Mind Illuminated: Lumosity and The Human Cognition Project
