In Marian Diamond's book, Magic Trees of the Mind, she discusses her views on enrichment – the idea that positive experiences can have an effect on brain development. In the introduction and first chapter of her book, she explains her journey of proving these theories on enrichment through the study of rats. She states, "the brain's outer layer can grow if a person or animal lives in stimulating surroundings, but the zone can shrink if the environment is dull or unchallenging" (p.2). This outer layer, known as the cortex, was found to be thicker in rats that were placed in a stimulated environment and thinner in the other rats who were unstimulated. The main cell of a brain, called a neuron, and it's distinct parts, has shown to respond to stimulating environments. Diamond describes, "neurons in the rat's cerebral cortex were sending out more dendritic branches in response to environmental stimulation. Holloway also found that this branching, at least in part, was causing the cortex to grow thicker" (p.23). Also part of the dendrite of a neuron is the area in which a synapse, the area where a chemical message is sent, occurs at little protrusions called spines. "These, spines, in turn, twitch and vibrate in response to inflowing information, and the transmission process itself transmutes their shape. In some way, the shimmering, pulsating neural arbors help modulate learning and memory. And the more stimulating the animal's environment, the more extensive the arbor" (Diamond, p.27). .
Beyond all this science, the main message being sent is the importance of our environment. How we want the outcome of our children and future generations all starts from even before they are born! Diamond describes the "trees of the mind" as the dendrites. She shows pictures of the "trees" at different ages and what is amazing is how expansive these forests grow in such a small amount of time.