Autism Spectrum DisorderAutism and the Brain

Scientists believe that most autism symptoms are rooted in functional changes in the brain. Over the past 20 years, dozens of studies have investigated differences in brain structure and function in children and adults with autism. In general, the greatest differences are seen in young children diagnosed with autism; by the time people with autism reach adulthood, many of the most obvious structural changes disappear.^1,2 Nevertheless, some symptoms often remain, suggesting that more complex neuronal differences persist in the brain.

While there are variations across studies and each individual is unique, there are a few consistent themes:

• Early overgrowth & higher short-range connectivity: Many children with early diagnosed autism seem to have brains that are slightly larger than expected for their age. Scientists have suggested that this may be due to lack of neuronal “pruning”, where the brain naturally loses certain neurons during early childhood. Children with autism may have too few long-distance connections and too many short-distance connections between neurons.^2-4
• Lower long-range connectivity: Distant regions of our brains work together to help us manage complex tasks – using sensory information (sight, sound, taste, touch, internal sensations, etc.) to make decisions and understand activities in the world around us. Children with autism often have lower levels of long-range connectivity in the brain, making these complex brain activities more difficult.^3,5-7
• Difficulty with network switching: Undertaking a task like walking through a room requires our brains to coordinate many regions together, including vision, motor, decision making, and more. One theory of brain function holds that we have distinct “networks” for different types of thinking activities, where several regions of the brain work together in canonical patterns. Say a student was daydreaming in class, and then the teacher suddenly called on them to solve a math problem; in this instance, a network devoted to daydreaming would shut off, and a problem-solving network would turn on. People with autism seem to have altered networks and more difficulty switching between different networks.^8-11