What is the best way to wire a brain?
Jim Hutchins, professor of health sciences at Weber State University, delves into the synapses to find out.
Jim Hutchins was born in Texas and raised in Colorado. He has attended the University of Colorado, University of California at Berkeley, and Baylor College of Medicine. He completed his postdoctoral training with Vivien Casagrande at Vanderbilt University and taught at the University of Mississippi Medical Center for 16 years. He is now teaching at Weber State University in Ogden, Utah.
The Brain is Maintained by Chance the Gardener
There are 80 billion nerve cells, or neurons, in the human brain. Each of these neurons clasps 10,000 partners at synapses, where they use chemical signals to communicate with each other.
I’m a developmental neuroscientist, so my student researchers and I are very much interested in the question, “how did it get that way?” We know the rulebook for constructing a human brain has fewer and more cryptic instructions than an average IKEA chair. Yet, with only a small rulebook, we can still make all the connections we need to make to create a brain that can play Bach’s Suite Number Two in C Minor on a cello, or caress a lover, or swing at a baseball with incredible accuracy.
Early in brain development, as we leave our mothers’ wombs, we overproduce synapses. One-third of these contacts will not survive into adulthood. There is a Goldilocks zone of brain development: we are looking for a “just right” number of connections, not too many, and not too few. How does the developing brain pick winners and losers to get to “just right”?
We would think that having more connections is a good thing, and having fewer is a bad thing. It’s true that in intellectual disability, both the connections and their landing sites are sparser than in neurotypical individuals.
But in autism, researchers have shown that the differently-wired brain has too many, rather than too few, connections. The typical landing zones of synapses are called dendrites, by analogy with a tree. Neuroscientists use the term “pruning” to describe the shearing of synapses that are superfluous. Autistic individuals have what is called a “pruning defect”.
A gardener needs to prune to help fruit trees reach their maximum potential. The gardeners of the brain need to prune synapses, to help the brain reach its maximum potential.
