Autism is a developmental neurobiological disorder that manifests itself during the first three or four years of life and lasts throughout a person’s lifetime. Although each autistic syndrome is different in its symptomatology, this disorder is characterized by two common features: 1) persistent deficits in social communication and interaction across multiple contexts, and 2) restricted, repetitive patterns of behavior, interests, or activities (Volden, 2017).
Autism primarily involves behavioral deficits. However, numerous research studies have shown that the problem begins during prenatal brain development. Below, the most recent lines of research on the neurobiological causes leading to this disorder will be described.
1. Autism and brain volume. Researchers have found a correlation between the degree of excess brain growth and the severity of autism symptoms. Studies conducted using structural magnetic resonance imaging have specifically demonstrated that brain overgrowth starts in the first year of life, if not sooner (Amaral et al., 2017; Kessler, Seymour, & Rippon, 2016). Although the cause of this excessive brain growth is currently unknown, the new data represent great progress for the early diagnosis and treatment of autism.
2. Autism and abnormal organization of the cerebral cortex. From the first months of gestation, the cerebral cortex is organized into various areas that differ from one another. However, it has been observed that this differentiation does not occur in the same way in children with this disorder. Researchers, utilizing a tomography procedure, examined the postmortem tissue from children with autism and without this, all between the ages of 2 and 15 years. Clusters of disorganized brain cells were discovered in the prefrontal cortex, a brain region strongly associated with communication and social interaction (Sanz-Cortes, Egana-Ugrinovic, Zupan, Figueras, & Gratacos, 2014). Other subsequent studies have supported this finding, with defective neuronal development during the second and third trimesters of pregnancy, being one of the possible causes.
3. Autism and amygdalahypoactivation. The amygdala is the brain structure responsible for emotional processing. The amygdala’s role in emotion is so important that individuals with amygdala damage are incapable of recognizing other people’s emotions, expressing their own emotions, or even naming these emotions.