It’s not headline news that our brains are the seat of our thoughts and feelings. The brain is a body’s decision-maker, the pilot of its actions and the engineer that keeps all systems going. The brain suits the body’s actions to its surroundings, taking in sensory details and sending out appropriate and timely responses. We’ve long attributed the marvelous workings of the brain to the intricate structures formed by its highly specialized cells, neurons. These structures constitute the hardware of the brain.
But new genomic research reveals that, at an even deeper level, emotions and behavior are also shaped by a second layer of organization in the brain, one that we only recently created the tools to see. This one relies on genes.
We are beginning to appreciate how genes and neurons work together, like software and hardware, to make brain function possible. Learning to understand this two-layer system can help us understand how the environment affects behavior, and how to hack the system to improve mental health.
It is time to fully recognize gene activity not as the background utility of the brain, but as an integral part of its operation.
Neurons in the driver’s seat
The sheer complexity of the human brain became apparent in the late 19th century, when two skilled anatomists, Camillo Golgi of Italy and Santiago Ramón y Cajal of Spain, invented tissue-staining techniques that revealed intricate microscopic networks of neural cells.
We now know that about 100 billion neurons connect with each other in a human brain to form complex circuits that carry electrical and chemical messages to make memories and govern behavior. This physical structure, the one that yielded itself to the scientific tools of the time, constitutes the hardware of our neural control system, which is uniquely rewireable by experience.
Throughout the 20th century, scores of scientists characterized the sugars, lipids, proteins and myriad other molecules that build, run and repair our brains. These molecules seemed to stay out of the limelight; they appeared to play a supporting role to the neurons that ostensibly controlled our behavior.