New Speculations on the Cause of Sound Sensitivity

Many children with developmental disabilities, such as autism, Fragile X syndrome, and William’s Syndrome,suffer from sound sensitivity. The underlying reason for this problem is not understood. A recent study by Drs. Chen and Toth of Cornell University Medical College in New York provide some evidence that sound sensitivity may have a genetic cause. Their study examined genetically engineered mice who did not have the FMR-1 gene. The FMR-1 gene is inactive in people with Fragile X syndrome. These mice displayed unusually strong reactions to tones, and they were more likely to have seizures induced by sounds.

Dr. Karl Reichelt of the Pediatric Research Institute in Oslo, Norway hypothesizes that a defect in serotonin metabolism may be responsible for sound sensitivity in autism. Serotonin is a neurotransmitter related to arousal and inhibition; and it is known to be abnormal in many autistic individuals. Dr. Reichelt theorizes that there are relatively low levels of serotonin in the synaptic gap. [The synaptic gap is a small space between the neurons. Neurons are able to communicate with one another when one neuron, often referred to as the pre- synapse neuron, releases chemicals into the synaptic gap. Another neuron, referred to as the post-synapse neuron, is activated or inhibited when it receives (uptakes) the chemicals.] Dr. Reichelt suggests that there is an increased uptake of serotonin by the pre-synaptic neuron from the post-synaptic neuron, and this may be caused by a serotonin-uptake stimulating tripeptide. This tripeptide is related to the Reelin gene, a probable marker for autism. Consequently, there will be less serotonin in the synaptic gap, and this will lead to a hyposerotoninergic state and to problems in inhibiting stimulation in the central nervous system. For example, there would be little or no inhibition after sounds enter the central nervous system; and this would lead to sounds resounding and reverberating at full force in the brain.

Another possible cause of sound sensitivity is mercury poisoning. Many parents and professionals believe that the mercury preservative (i.e., thimerasol) used in many vaccines can cause autism. Research on mercury toxicity has clearly shown that it can cause sound sensitivity. We are hearing reports from parents whose children participated in a mercury detoxification program; and as a result, their sound sensitivity decreased or was eliminated. We have heard from a few parents whose children’s sound sensitivity increased slightly while receiving a mercury detoxification procedure. In these cases, the mercury may have been temporarily re-distributed to other places in the body.


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This article appeared in a previous issue of The Sound Connection, 2002, Vol. 9, No. 2, page 6.

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