Neurogenesis: Environment Matters to the Brain

Elizabeth Gould's research in neurogenesis—the process of creating new brain cells—is adding to our understanding of how our environment directly affects the quality of our thinking. A professor of psychology at Princeton University, she is changing our understanding of the production of new neurons and the plasticity of the brain.

The brain is a remarkably pliable organ that is greatly influenced by our surroundings. In chronically boring environments or stressful conditions, the structure of the brain is altered. Brain cells starve and retreat and new cells are not created. Yet remarkably, the brain can also heal itself. When the environmental conditions are enriched the brain begins to create new brain cells and the density of neuronal dendrites (the branches that connect one neuron to another). It would seem design—in all its various forms—matters.

In an article in Seed magazine, writer Jonah Lehrer reports on Gould’s research:

The subject of stress has been the single continuous thread running through Gould’s research career. From the brain’s perspective, stress is primarily signaled by an increase in the bloodstream of a class of steroid called glucocorticoids, which put the body on a heightened state of alert. But glucocorticoids can have one nasty side-effect: They are toxic for the brain. When stress becomes chronic, neurons stop investing in themselves. Neurogenesis ceases. Dendrites disappear. The hippocampus, a part of the brain essential for learning and memory, begins withering away.

The social implications of this research are staggering. If boring environments, stressful noises, and the primate’s particular slot in the dominance hierarchy all shape the architecture of the brain—and Gould’s team has shown that they do—then the playing field isn’t level. Poverty and stress aren’t just an idea: they are an anatomy. Some brains never even have a chance.

Gould’s work implies that the symptoms of poverty are not simply states of mind; they actually warp the mind. Because neurons are designed to reflect their circumstances, not to rise above them, the monotonous stress of living in a slum literally limits the brain.

On a cellular level, the scars of stress can literally be healed by learning new things. Genia Kozorovitskiy, an effusive graduate student who began working with Gould as a Princeton undergrad, has studied the effects of various environments on their colony of marmosets. As predicted, putting marmosets in a plain cage—the kind typically used in science labs—led to plain-looking brains. The primates suffered from reduced neurogenesis and their neurons had fewer interconnections. However, if these same marmosets were transferred to an enriched enclosure—complete with branches, hidden food, and a rotation of toys—their adult brains began to recover rapidly. In under four weeks, the brains of the deprived marmosets underwent radical renovations at the cellular level. Their neurons demonstrated significant increases in the density of their connections and amount of proteins in their synapses.

The mind is like a muscle: it swells with exercise. Gould’s and Kozorovitskiy’s work reminds us not only how easy it is to hurt a brain, but how little it takes for that brain to heal. Give a primate just a few extra playthings, and its neurons are capable of escaping the downward cycle of stress.

The research should give us pause to consider the environment we function in and the environment we create for others to perform in.