Tone-deaf people--those who can't hold a tune--appear to be missing a specific neural circuit, according to research published today in the Journal of Neuroscience.

Researchers used a variation of MRI called diffusion tensor imaging to compare neural circuits--specifically those between the right temporal and frontal lobes--in the brains of people who are tone-deaf and those who are not.

According to a press release from the Society for Neuroscience, which published the research,

This region, a neural "highway" called the arcuate fasciculus, is known to be involved in linking music and language perception with vocal production.The arcuate fasciculus was smaller in volume and had a lower fiber count in the tone-deaf individuals. More notably, the superior branch of the arcuate fasciculus in the right hemisphere could not be detected in the tone-deaf individuals. The researchers speculated that this could mean the branch is missing entirely, or is so abnormally deformed that it appears invisible to even the most advanced neuroimaging methods.

A new nanoparticle contrast agent gives a clearer picture of a mouse's brain tumor in both MRI and optical images (left column) than is possible without the agent (right column). The tumor is located in the cerebellum. Credit: Cancer Research

Researchers at the University of Washington, Seattle have made the first imaging nanoparticle that can cross the blood-brain barrier. The nanoparticle, which specifically targets tumor cells, might help surgeons better pinpoint the boundaries of brain tumors.

The blood vessels that serve the brain are much more selective about what gets through than those feeding the rest of the body's organs. This helps protect the brain from infection, but it also makes it difficult to get drugs and image-contrast agents inside the brain. The barrier can be temporarily broached using drugs, but at the risk of infection. This has made it difficult to apply recent developments in the field of molecular imaging, which uses targeted nanoparticles to light up tumor cells, to the brain. Targeted imaging could be particularly useful for imaging brain tumors, since these tend to be very invasive, infiltrating the surrounding brain tissue, making it difficult to remove them without damaging surrounding tissues, leading to cognitive problems.

The Seattle researchers developed a nanoparticle that is visible on magnetic resonance imaging scans and under the near-infrared light used by surgical microscopes. They tuned the particle's properties--size, fat content, and electrical charge--so that it could cross the blood-brain barrier. It's made up of an iron-oxide sphere coated with a fluorescent protein and a protein that's targeted to tumor cells. When administered through a blood vessel to mice carrying brain tumors, the nanoparticle, which is described this week in the journal Cancer Research, improved contrast in brain imaging scans.

Credit: Ren West

Stem cells from frog eggs can be genetically prodded to develop into functional eyes in tadpoles, according to research presented at the Society of Neurosciences conference in Washington, DC. Michael Zuber and his colleagues from SUNY Upstate Medical University, in Syracuse, NY, genetically engineered the stem cells to express a set of transcription factors (proteins that trigger expression of other genes) that are known to regulate eye development.

When transplanted onto frog embryos that had had one eye removed, the cells developed into all seven types of cells found in the retina and also grew connections to the appropriate target in the brain. Swim tests showed that the new eyes functioned properly: tadpoles stayed in the part of their tank with a white background, which is normal tadpole behavior, rather than a black background.

It's not clear if the same genetic programming would work in mammalian cells: frogs have much greater regenerative potential than mammals to begin with, and it's difficult to simultaneously express all the required transcription factors in mammalian cells for technical reasons. But Zuber hopes to use the frog system to find chemicals that activate the transcription factors without genetic engineering. If successful, the research might one day lead to new treatments for diseases linked to cell loss in the retina.

In related findings, Sujeong Jang of Chonnam National University, in South Korea, and colleagues were able to restore hearing in deafened guinea pigs by transplanting neural stem cells derived from human bone marrow.

Restoring sight: Scientists removed one eye from tadpoles (left image) and then implanted genetically engineered stem cells in its place. They grew to form a functioning eye (right). Credit: Michael Zuber