November 16, 2010

Hearing Over the Noise

(Ivanhoe Newswire) --Tired of the old pick up line "In a room full of people all I hear is you?"  Well, research reveals that may be true. A study found that brains of bats tell some neurons to 'shush' and others to 'yell louder' in order for key sounds to be heard above background noise"”a process that may be working in humans as well.

"Some neurons seemed to know to yell louder to report communication sounds over the presence of background noise," Bridget Queenan, a doctoral candidate in neuroscience at Georgetown University Medical Center, was quoted as saying. "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."

In this study, Queenan and her colleagues presented different combinations of echolocation sounds with various communication sounds to awake bats to see how neurons in the bat brains were dealing with this incredible cacophony. The researchers found that some bats' neurons control the activity of other neurons when important sounds are perceived. The scientists also found other neurons that amp up perception of bat communication in the face of background noise. Working together, these clumps of neurons allow the bats to hear what is needed.

"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 says. "In fact, bats have a whole host of communication sounds: angry sounds, warning sounds, and sounds that says 'please don't hurt me."

The auditory processing area in bats' brains is larger than other centers, just like the visual processing center in humans is large. "Humans operate predominantly by sight so a huge portion of our brain is devoted to vision processing. Bats, however, operate by sound," Queenan added.

"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," Queenan says. "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."

Queenan says her next task is to record brain neurons in bats that are not only awake, but also flying.

SOURCE: Georgetown University Medical Center, November 2010