The Brain and the Eyes
I was struck by a section of a recent New Yorker article about schizophrenia and its genetic characteristics by Siddhartha Mukherjee, titled, “Runs in the Family.” For me this excerpt represents the value of having a skilled journalist take on complicated scientific issues. And, of course, this is about what’s happening to babies, Maryland Family Network’s sweet spot!
The human eye is born restless. Neural connections between the eyes and the brain are formed long before a child is born, establishing the wiring and the circuitry that allow her to begin visualizing the world the minute she emerges from the womb. Long before the eyelids open, during the early development of the visual system, waves of spontaneous activity ripple from the retina to the brain, like dancers running through their motions before a performance. These waves reconfigure the wiring of the brain—rehearsing its future circuits, strengthening and loosening the connections between neurons. (The neurobiologist Carla Shatz, who discovered these waves of spontaneous activity, wrote, “Cells that fire together, wire together.”) This fetal warm-up act is crucial to the performance of the visual system: the world has to be dreamed before it is seen.
During this rehearsal period, synapses between nerve cells are generated in great excess, to be pruned back during later development. The elimination of synaptic connections, which results in the constant refinement of neural circuits, like the soldering and resoldering of wires on a circuit board, is not a feature unique to the visual system. Throughout the brain—particularly in the parts involved in cognition, memory, and learning—synapse pruning continues into our first three decades, which suggests that it may be responsible, in part, for the starburst of adaptive learning that characterizes the first decades of human life. We are hardwired not to be hardwired, and this anatomical plasticity may be the key to the plasticity of our minds.