"Throughout the study period, vaccinated animals showed an increase in total brain volume a feature of the brain in many young children with autism - when compared with unvaccinated animals. However, a specific part of the brain associated with emotional responses that is thought to be important in autism, the amygdala, did not show abnormalities until after the 12-month vaccines had been given. In addition, after the 12-month vaccines only, the functional brain scans showed significant differences between vaccinated and unvaccinated groups. These functional scans looked at the activity of receptors for morphine-like compounds (opioids) that may play a role in the brain of children affected by autism. Vaccine administration was associated with an increase in opioid binding activity in the amygdala compared with a decrease in the unvaccinated group."