Between the ear and brain, an orderly orchestra of synapses

June 05, 2012

BUFFALO, N.Y. -- The brain receives information from the ear in a surprisingly orderly fashion, according to a University at Buffalo study scheduled to appear June 6 in the Journal of Neuroscience.

The research focuses on a section of the brain called the cochlear nucleus, the first way-station in the brain for information coming from the ear. In particular, the study examined tiny biological structures called synapses that transmit signals from the auditory nerve to the cochlear nucleus.

The major finding: The synapses in question are not grouped randomly. Instead, like orchestra musicians sitting in their own sections, the synapses are bundled together by a key trait: plasticity.

Plasticity relates to how quickly a synapse runs down the supply of neurotransmitter it uses to send signals, and plasticity can affect a synapse's sensitivity to different qualities of sound. Synapses that unleash supplies rapidly may provide good information on when a sound began, while synapses that release neurotransmitter at a more frugal pace may provide better clues on traits like timbre that persist over the duration of a sound.

UB Associate Professor Matthew Xu-Friedman, who led the study, said the findings raise new questions about the physiology of hearing. The research shows that synapses in the cochlear nucleus are arranged by plasticity, but doesn't yet explain why this arrangement is beneficial, he said.

"It's clearly important, because the synapses are sorted based on this. What we don't know is why," said Xu-Friedman, a member of UB's Department of Biological Sciences. "If you look inside a file cabinet and find all these pieces of paper together, you know it's important that they're together, but you may not know why."

In the study, Xu-Friedman and Research Assistant Professor Hua Yang used brain slices from mice to study about 20 cells in the cochlear nucleus called bushy cells, which receive information from synapses attached to auditory nerve fibers.

The experiments revealed that each bushy cell was linked to a network of synapses with similar plasticity. This means that bushy cells themselves may become specialized, developing unique sensitivities to particular characteristics of a sound, Xu-Friedman said.

The study hints that the cochlear nucleus may not be the only part of the brain where synapses are organized by plasticity. The researchers observed the phenomenon in the excitatory synapses of the cerebellum as well.

"One reason this may not have been noticed before is that measuring the plasticity of two different synapses onto one cell is technically quite difficult," Xu-Friedman said.
-end-


University at Buffalo

Related Brain Articles from Brightsurf:

Glioblastoma nanomedicine crosses into brain in mice, eradicates recurring brain cancer
A new synthetic protein nanoparticle capable of slipping past the nearly impermeable blood-brain barrier in mice could deliver cancer-killing drugs directly to malignant brain tumors, new research from the University of Michigan shows.

Children with asymptomatic brain bleeds as newborns show normal brain development at age 2
A study by UNC researchers finds that neurodevelopmental scores and gray matter volumes at age two years did not differ between children who had MRI-confirmed asymptomatic subdural hemorrhages when they were neonates, compared to children with no history of subdural hemorrhage.

New model of human brain 'conversations' could inform research on brain disease, cognition
A team of Indiana University neuroscientists has built a new model of human brain networks that sheds light on how the brain functions.

Human brain size gene triggers bigger brain in monkeys
Dresden and Japanese researchers show that a human-specific gene causes a larger neocortex in the common marmoset, a non-human primate.

Unique insight into development of the human brain: Model of the early embryonic brain
Stem cell researchers from the University of Copenhagen have designed a model of an early embryonic brain.

An optical brain-to-brain interface supports information exchange for locomotion control
Chinese researchers established an optical BtBI that supports rapid information transmission for precise locomotion control, thus providing a proof-of-principle demonstration of fast BtBI for real-time behavioral control.

Transplanting human nerve cells into a mouse brain reveals how they wire into brain circuits
A team of researchers led by Pierre Vanderhaeghen and Vincent Bonin (VIB-KU Leuven, Université libre de Bruxelles and NERF) showed how human nerve cells can develop at their own pace, and form highly precise connections with the surrounding mouse brain cells.

Brain scans reveal how the human brain compensates when one hemisphere is removed
Researchers studying six adults who had one of their brain hemispheres removed during childhood to reduce epileptic seizures found that the remaining half of the brain formed unusually strong connections between different functional brain networks, which potentially help the body to function as if the brain were intact.

Alcohol byproduct contributes to brain chemistry changes in specific brain regions
Study of mouse models provides clear implications for new targets to treat alcohol use disorder and fetal alcohol syndrome.

Scientists predict the areas of the brain to stimulate transitions between different brain states
Using a computer model of the brain, Gustavo Deco, director of the Center for Brain and Cognition, and Josephine Cruzat, a member of his team, together with a group of international collaborators, have developed an innovative method published in Proceedings of the National Academy of Sciences on Sept.

Read More: Brain News and Brain Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.