Autism is associated with many causes. All must affect a common vulnerable system within the brain that disrupts normal development of language and social awareness. Nuclei in the brainstem auditory pathway have greater blood flow than other areas of the brain, thus are more exposed to any toxic substance in the circulation.
High blood flow in the inferior colliculus (plural colliculi) supports the highest metabolic activity in the brain. This small nucleus in the midbrain serves an auditory alerting function for visual attention. High metabolic activity in this small midbrain center continues even during sleep, and provides a vigilance function for environmental awareness.
Vigilance is enhanced by active information-seeking mechanisms, or selective response to acoustic stimuli of special importance. Species-specific vocal calls are a priority for social interactions. Human language is at the pinnacle of mechanisms for alerting, vigilance, and awareness of others.
The inferior colliculi were found more than 50 years ago to sustain injury from asphyxia at birth. This should long ago have been considered relevant to developmental language disorders. Evidence is presented here that integrity of these small nuclei is essential for learning to speak, for maturation of the language areas of the cerebral cortex, and for full development of social awareness.
