14 DAY TRIAL // The best way to find out how do people or animals manage to focus on some sounds and ignore others, is to analyze a bat's brain, and Bridget Queenan, a doctoral candidate in neuroscience at Georgetown University Medical Center, was able to identify some pieces of this puzzle.
Neuroscientists from the Georgetown University Medical Center, discovered that the brains of bats can make some neurons silent and others 'yell louder', so that certain sounds can be heard above background noise.
Queenan explained that “all organisms are constantly assaulted by incoming stimuli such as sounds, light, vibrations, and so on, and our sensory systems have to triage the most relevant stimuli to help us survive.
“As humans we are not only sensitive to a child's cry, but we notice flashing ambulance lights even though we are engrossed in something else.
“We want to know how that happens.”
After analyzing the brain of the mustached bat, the researchers found that there are some neurons that seem to quiet down the others as important communication sounds come in, and Queenan suggests that the process might be the same for humans.
She also reports that “some neurons seemed to know to yell louder to report communication sounds over the presence of background noise.
“So we can now start to piece together how the cells in your brain are able to deal with the complex sensory environment we live in.”
Bats are very interesting animals to understand auditory brain function on, because they use echolocation – a kind of biological sonar, to process sound.
They call out and listen to the echo produced by their ultrasounds bouncing off nearby objects, and manage to navigate and hunt in this way.
Along with her colleagues, Queenan made a huge noise by combining different combinations of echolocation sounds with several communication sounds which awoke the bats, in order to see the way that their neurons dealt with the situation.
They found out that when the bats perceived important sounds, some neurons controlled the activity of other neurons.
GUMC researchers also discovered that there was another group of neurons that amplified the perception of bat communication, so it becomes louder than the background noise.
When these two groups of neurons worked together, the bat could hear what it needed to.
Queenan explained that not only do the brains of bats process a constant stream of pulses and echoes, they also manage the bats' social communication.
“What we are trying to figure out is how a bat can fly around echolocating - screeching and listening to its own individual sounds bouncing back - amidst a whole colony of hundreds of other echolocating bats – and possibly hear another bat saying 'watch out!
“Bats actually do make these cautious calls quite a bit,” Queenan added.
“In fact, bats have a whole host of communication sounds: angry sounds, warning sounds, and sounds that says 'please don't hurt me.”
The entire process in bats' brain is possible because the auditory processing area is larger than the other centers, just like the visual processing center in humans is.
“Humans operate predominantly by sight so a huge portion of our brain is devoted to vision processing. Bats, however, operate by sound,” explained Queenan.
Queenan's next mission is to record brain neurons in bats that are not only awake, but flying.
The research will be presented at the annual meeting of the Society for Neuroscience in San Diego.