Saturday, July 25, 2009

The Biology of Auditory Processing - Sound Sensitivity

Parents and teachers may have found this maddening - children who have strong aversiveness to sounds that they flee the classroom, birthday parties, baseball games, and movie theatres, but perplexed expressions from audiologists who tell them that their child's hearing is completely normal. In our clinic was see auditory aversive (want to escape) behaviors in many conditions (for instance premature birth, CAPD, mild birth injury, autism spectrum disorders). In these paired studies, it becomes clearer why audiology tests didn't explain behaviors.

For many different reasons, children can develop fight-or-flight reactions to sound that result from the brain overactivation of brain regions like the amygdala. Because different conditions can cause this, there are probably different ways this miswiring or misactivation occurs. In the figure below, see how much more cortical activation children with auditory sensitivity have with sound. Their auditory cortex overreacts to sound stimuli - no wonder it causes panic and danger reactions.

The McGill researchers recommend using a different terminology to describe sound sensitivity (these terms are similar to terms found in other sensory systems).

True Hyperacusis: Lowered hearing thresholds
Odynocusis: Lowered auditory pain threshold
Auditory Allodynia: Aversion or fear of sounds not normally aversive
Auditory Attractions: Attractions to or fascinations with certain sounds



Williams Hyperacusis and Sound Aversion pdf
Williams, fMRI, Amygdala pdf

3 comments:

  1. This comment has been removed by a blog administrator.

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  2. Fernette,
    Would the four terms listed above fall into the Sensory Modulation Disorder pattern of SPD? Or is it not that cut-and-dry?
    Thanks,
    Ida
    www.sensorystreet.com

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  3. Based on my understanding, these would be under the OT definitions of SMD. From the medical standpoint, though the above definitions have different causal / treatment implications. OTs are usually dealing with all the senses at once, while auditory specialists are dealing with just hearing. The approaches are complementary, and some benefits are to be had with focused intervention vs. more holistic, and vice-versa.

    But in the end, the differences in terminology and the changes in terminology over the years have only resulted in a more murkiness and confusion, I think.

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