June 19, 2019

Good Morning,

If you have an appreciation for music then you should thank your brain for that. A neuroscientist has discovered that the human brain is remarkably tuned to enjoy music and sound. This is something music fans need to hear.

Learn about this and more interesting stories from the scientific community in today's issue.

Until Next Time,
Erin

Questions? Comments? Scientific Discoveries? Email Us

*-- Human brain uniquely tuned for musical pitch --*

The human brain is uniquely tuned to appreciate music, according to a new study.

"We found that a certain region of our brains has a stronger preference for sounds with pitch than macaque monkey brains," neuroscientist Bevil Conway, an investigator at the National Institutes of Health's Intramural Research Program, said in a news release. "The results raise the possibility that these sounds, which are embedded in speech and music, may have shaped the basic organization of the human brain."

The idea for the new study came while Conway was working at MIT. Conway and Sam Norman-Haignere, a post-doctoral fellow at Columbia University's Zuckerman Institute for Mind, Brain, and Behavior, were trying to identify differences in the way monkey and human brains manage vision. They didn't have much success.

Norman-Haignere was also studying hearing in the laboratory of Josh H. McDermott.

"I told Bevil that we had a method for reliably identifying a region in the human brain that selectively responds to sounds with pitch," Norman-Haignere said.

The two researchers decided to compare how human and monkey brains control hearing. For the study, Conway, Norman-Haignere and their colleagues played a series of harmonic sounds for healthy volunteers and monkeys. Functional magnetic resonance imaging allowed the researchers to monitor the participants' brain activity.

Researchers also played toneless sounds that matched the frequencies of the harmonic sounds.

The brains of both monkeys and humans showed similar levels of neural activity in response to non-harmonic sounds. But the neural patterns showed humans were more sensitive to tonal sounds.

"We found that human and monkey brains had very similar responses to sounds in any given frequency range. It's when we added tonal structure to the sounds that some of these same regions of the human brain became more responsive," said Conway. "These results suggest the macaque monkey may experience music and other sounds differently. In contrast, the macaque's experience of the visual world is probably very similar to our own. It makes one wonder what kind of sounds our evolutionary ancestors experienced."

When scientists repeated the experiment using sounds that contained natural harmonies for monkeys, including macaque calls, they got the same results. The researchers published their findings this week in the journal Nature Neuroscience.

"This finding suggests that speech and music may have fundamentally changed the way our brain processes pitch," said Dr. Conway. "It may also help explain why it has been so hard for scientists to train monkeys to perform auditory tasks that humans find relatively effortless."

*-- Plankton species uses bioluminescence to scare off predators --*

At least one species of dinoflagellate plankton uses its bioluminescence for defensive purposes.

Researchers determined the species Lingulodinium polyedra uses its glow-in-the-dark abilities to scare off copepod grazers, the species' primary predator.

According to the new study -- published this week in the journal Current Biology -- the bioluminescent cells sense low concentrations of copepodamides, polar lipids emitted by copepod grazers, a group of small crustaceans.

"This in turn helps to better protect them from their grazers, letting them survive longer to reproduce and therefore compete better within the plankton," Andrew Prevett of the University of Gothenburg, Sweden, said in a news release.

Researchers used low-light, high-speed cameras to observe the behavior of dinoflagellate plankton. Film footage showed the plankton's bioluminescence cells flashed when touched by the grazers. Video evidence also proved grazers frequently declined to eat glowing dinoflagellate plankton.

Dinoflagellate plankton were much less likely to be consumed by copepods. The protection provided by bioluminescence may explain why the plankton, which grow much more slowly than their peers, are able to persist in competitive marine ecosystems.

"Earlier studies had shown that dinoflagellates with naturally brighter bioluminescence than L. polyedra were grazed less but still required cell concentrations to be relatively high before all grazing on the bioluminescent cells ceased," Prevett said. "L. polyedra abundance in our study is low by comparison, and we were surprised at how effective the bioluminescence defense became despite this."

Scientists aren't sure how exactly bioluminescence works as a defense mechanism. There are three basic theories.

Some researchers suggest the bright flash tricks predators into thinking the plankton are toxic or harmful. Others theorize that the bioluminescence works like a flash-bang, startling the predator -- either triggering an escape response by the copepod or startling the crustacean long enough to allow the dinoflagellate to escape.

"The third theory suggests that the flash acts as a form of burglar alarm, attracting the attention of a larger visual predator, like a fish, which could track and consume the copepod," Prevett said. "There is evidence to support each of these theories and bioluminescence protection could be combinations of some or all of the above."

In follow-up studies, researchers plan to explore the ways the fear of being eaten influences the structures and organization of ecosystems.

"These indirect effects of consumers are understudied in unicellular dominated food webs such as marine plankton," Prevett said. "This paper and other similar results suggest that indirect predator effects are strong drivers in the microscopic food web of the oceans too."