Children and adults with Autism Spectrum Disorders (ASD) typically demonstrate significant abnormalities in their processing of auditory information (sound). These individuals appear to not hear well or not hear at all. Brain imaging studies reveal weaknesses in multiple areas of the auditory system. The following weaknesses are just some of the auditory deficits that can present in the pediatric or adult individual on the autism spectrum.
Problems with regulating accurate loudness perception and accurately identifying how sensory stimuli affect emotion. Sounds that are not judged to be either loud or bothersome to the non-ASD individual are often judged to be too loud or frightening to the individual with ASD. In a typical developing child, a sound that may be loud and frightening as a young baby becomes no longer so as the limbic system develops. The poorly developed limbic system in ASD individuals is responsible for the inaccurate classification of loudness.
Hypersensitivity to sound (hyperacousis) resulting from damage to several areas along the auditory pathway, including the planum temporale and Heschl's gyri. Similar to the poor loudness regulation, Individuals with ASD may cry or express fear because sounds "hurt" their ears. Common sounds that are uncomfortably loud include the sound of water running, the toilet flushing, cafeteria noise, the sound of the school bus coming down the road, or the vacuum running.
Difficulty hearing in the presence of background noise in part due to reduced function of the outer hair cells in the cochlea and medial olivocochlear bundle. The outer hair cells are responsible for finely tuning sound and improving the signal to noise ratio.
Abnormal vertical sound localization of sound resulting from significantly smaller and rounder superior olivary complex portion of the auditory system.
Difficulty recognizing emotion in others' voices due to dysfunction of the superior temporal gyrus and other auditory- and language- related regions in the brain.
It is important to keep in mind that in addition to the above auditory dysfunction, hearing loss as well can co-occur in the individual with ASD, creating a tower of hearing and listening problems. It is essential that all individuals with ASD undergo a complete audiological evaluation with a licensed audiologist to conclusively identify auditory impairment. Additionally, audiologists who specialize in sound sensitivity treatment can play an important role in treatment of sound sensitivity as part of compressive language, cognitive, and educational intervention.
Understanding of these anatomical brain differences in children and adults with ASD should cause us to have compassion on the child or adult with ASD. Sounds really do "hurt" their ears, and the vast auditory and language dysfunction creates significant difficulties with understanding spoken language and processing the world around them. Very early intensive intervention can rewire the brain and mitigate many ASD behaviors. But during our interactions, we should be kind and compassionate, and be thankful for each of our blessings in the process.
Sharon Macner, Au.D.
Doctor of Audiology
Danesh AA, Abdelhakiem MK. Auditory Manifestations and Intervention in Children with Autism Spectrum Disorders. 2015;1(1): 1005.