Zebrafish are helping University of Queensland scientists discover how sound processing impacts people with autism spectrum disorder and Fragile X syndrome.

The tiny fish carry the same genetic mutations as humans with both conditions, allowing researchers to discover the neural networks and pathways that produce the hypersensitivities to sound in both species.

A team of scientists from UQ studied how zebrafish made sense of their world, in order to explore how neurons work together to process information.

Fragile X syndrome is caused by the disruption of one gene, so researchers were able to disrupt that single gene in zebrafish and observe the effects.

Half of males and one fifth of females with Fragile X syndrome also meet the diagnostic criteria for autism spectrum disorder.

Queensland Brain Institute’s Dr Lena Constantin said loud noises often caused sensory overload and anxiety in people with autism and Fragile X syndrome.

“Sensitivity to sound is common to both conditions,” she said.

“We think the brain is transmitting more auditory information because it is not being filtered and adjusted as normal.”

As part of the study, Dr Constantin said the team recorded the brain activity of zebrafish larvae whilst showing them movies or exposing them to bursts of sound.

“The movies simulate movement or predators —the reaction to these visual stimuli was the same for fish with Fragile X mutations, and those without,” Dr Constantin said.

“But when we gave the fish a burst of white noise, there was a dramatic difference in the brain activity in Fragile X model fish.”

After seeing how the noise radically affected the fish brain, the team designed a range of 12 different volumes of sound.

Testing found that the Fragile X model fish could hear much quieter volumes than the control fish.

“The fish with Fragile X mutations had more connections between different regions of their brain,” said Dr Constantin.

“And their responses to the sounds were more plentiful in the hindbrain and thalamus,” Dr Constantin said.

Using the zebrafish, scientists have been able to see significantly more detail, and for the first time, witness more activity in the hindbrain, an area Dr Constantin said they’d like to explore further.

“We hope that by discovering fundamental information about how the brain processes sound, we will gain further insights into the sensory difficulties faced by people with Fragile X syndrome and autism,” she said.

The research was published in BMX Biology and funded by the Simons Foundation Autism Research Initiative, National Health and Medical Research Council and Australian Research Council.