Decoding Neurodevelopment: Findings on Environmental Exposures and Synaptic Plasticity

What makes one person different from the next? In large part it’s that our individual brains are wired a bit differently; each neuron in each person’s brain has a different set of synapses connecting to a different set of neurons. When we’re born, most of the major functional subregions of the brain and their interconnections are in place, but various experiences and environmental exposures affect which synaptic connections become stronger and which become weaker. Different areas of the brain have this synaptic plasticity—or ability to grow stronger or weaker connections—at different time periods, and the timing of these “critical periods” is tightly regulated. Thermogram showing hormone receptors in the hippocampus of an infant. Exposures to certain neurotoxic agents during critical periods of synaptic plasticity may set the stage for developmental disorders. © Explorer/Photo Researchers, Inc. The field of neurobiology is humming with new findings on the intricate workings that orchestrate this process, too many to describe in one story. But of special interest are key discoveries by investigators at the National Institute of Environmental Health Sciences (NIEHS) about some of the basic mechanisms involved in synaptic plasticity, and work by other investigators that explores the hypothesis that environmental toxicants that disrupt synaptic plasticity at critical periods play a role in disorders that have roots in early brain development, such as autism spectrum disorders (ASDs), attention deficit/hyperactivity disorder, and schizophrenia.1,2