What is an important discovery in neuroscience about how the brain is constructed?

• A. The brain is fixed at birth.
• B. The brain is constructed by experience.
• C. Genetics entirely determines brain development.
• D. Neurons are uniform in structure.

Answer: (B)

Experience shapes how the brain develops and organizes itself. Genetics provides the initial plan, but the actual wiring—how strong connections become, which circuits form, and even which neurons persist—changes with activity and environmental input. This plasticity shows up in synaptic strengthening with use, pruning of unused connections, and growth of dendrites in response to stimulation, with especially influential periods (critical periods) when sensory experiences have lasting effects. Even in adulthood, learning and recovery from injury can rewire networks. Because of this flexible, experience-driven construction, the idea that the brain is built by experience best fits what we know, whereas notions that it’s fixed at birth, entirely gene-determined, or that neurons are uniform across the brain don’t match the evidence.