Rebecca Poulsen, also known by her performance name BeXta, has entertained audiences around the world for years as a prolific musical producer and DJ. But Poulsen isn’t only interested in the audio stimulation of mere human ears; a self-described “neuroscience DJ,” she is also uncovering new insights into the acoustic sensitivities of zebrafish.
As the lead author of a new study published in Current Biology, Poulsen put her DJ skills to work for science by designing a tiny speaker system that pumped sounds into a tank containing zebrafish larvae. The baby fish are so small that it was possible to conduct whole-brain imaging of their neural responses to various noises, which revealed “a more nuanced auditory system than has previously been described in larval fish,” according to the study.
“A lot of the research in the past has been based on trying to determine the hearing range of the larvae, or using sounds to startle the fish behaviourally, so often only single frequencies or a single type of stimulus have been used,” said Poulsen, a PhD candidate at the Queensland Brain Institute at the University of Queensland in Brisbane, in an email.
“Although I included lots of single frequencies in my experiment, I also wanted to look at some more of the complex components of sound,” she added.
To accomplish this aim, Poulsen and her colleagues designed a speaker that measured roughly a half-inch across, and attached it to a small chamber containing zebrafish larvae, each of which was about three millimeters in size. The fish were placed in a jellied substance that allowed them to breathe while also keeping them still so that their brains could be effectively imaged.
“The speaker system was designed around the complexities of the microscope and equipment we use in the lab,” Poulsen explained. “We image a single fish at a time in a small chamber and there is no room for underwater speakers.”
“When you play sound through air to something in water, the sound changes, and is very inaccurate—it’s hard to know what sounds reach the fish,” she continued. “This system delivers the sound directly into the water really close to the fish. The hope was it is a really accurate sound system, so what we see in our data reflects the capabilities of the fish.”
The team piped in different acoustic stimuli, including single pure-tone frequencies, white noise, sharp punctuated sounds, and sounds that gradually rose in volume over time. The responses of zebrafish to these noises, revealed in the brain images, showed a broader sensitivity to frequencies than had been previously observed: the larvae seemed sensitive to frequencies of up to 4 kHz, though their neural patterns suggested they could only discriminate between frequencies at levels below 2.5 kHz.
“We found there were categories of neurons that respond uniquely to these different components,” Poulsen said. “This is important when you look at the sounds heard in nature. A baby fish needs to be able to tell the difference between running water, something hitting the water, and an approaching predator, for them to survive.”
The research also has applications for studying sensory processing and conditions in humans, such as autism and Fragile X syndrome, a topic that Poulsen has also studied using zebrafish models.
In addition to the carefully selected sounds piped into the chamber, Poulsen channeled her DJ skills for the fish, letting them listen to some of her own beats as well as classics like MC Hammer’s “U Can’t Touch This.” To her delight, MC Hammer retweeted the preprint of the study and has been actively promoting news coverage of the research since it was published on Tuesday.
“I was very excited when MC Hammer retweeted the preprint!” Poulsen said. “He has just retweeted the paper and the video with his music playing which is exciting too! The paper that has just been published focused on those basic components of sound, and from there we can build on more complex types of sound, even music.”
“After one of the experiments, we played ‘U Can’t Touch This’ to a fish and although the data is not analysed, it is interesting to watch different neurons respond to different sounds,” she noted. “Music and neuroscience is definitely an interest of mine and it would be fascinating to play more music in the future.”
Indeed, her dual artistic and scientific careers offer an expression of her deep passion for both fields.
“I guess the link between my music career and studying auditory neuroscience is firstly how much I love them both, but also that sound is so complex, and it’s fascinating how sophisticated human, and even fish brains are, at being able to decipher the acoustic world around them,” Poulsen said.