fMRI leaps forward….

A fantastic paper just out about relating the cellular microenvironment to the R2t* component of the signal relaxation constant, here. The authors did two really clever things: first they related the signal from the brain microenvironment (think, the area around individual synapses) to the Default Mode Network–a signature of resting awake cognitive activity. Second, they used the Allen Gene Brain atlas to look at the interplay between this brain imaging signal and the gene networks that define the molecular biology of the nervous system.

Definitely an important result. All of this out of the outstanding group at Washington University St. Louis that has been pushing the limits in this field.

The dangers of looking to closely

They’re called incidental findings in brain imaging research on “normal volunteers”. In today’s NY Times Gina Kolata looks at microbleeds in the brain:

“If there were more than we knew of in the general population, that might — and I want to stress might — have important consequences,” Dr. Breteler said. “That is why we started to look for them.”

For more than a decade, Dr. Breteler and her colleagues have followed a group of Rotterdam residents age 45 and older. The goal is to do repeated brain scans on 8,000 people; so far they have scanned nearly 4,000 and are analyzing those data.

“What we found came as a big surprise,” Dr. Breteler said. Previous estimates were that 5 to 7 percent of healthy older people had microbleeds. The Rotterdam study found them in more than 20 percent. And the older the person, the more likely the microbleeds. They were present in 18 percent of 60-year-olds and nearly 40 percent of those over 80.

“We now know that these changes are there and that they are frequent,” Dr. Breteler said. “But we don’t know yet what their clinical impact is, what their prognosis is.”

When MRI can do what PET can…

One of the advantages of positron emission tomography is its ability to probe the molecular aspects of brain function. Of course PET is quite invasive: your brain is injected with radioactive material.

Now MRI is going molecular without the radioactive burden.

Money quote from the press release:

In this report, Harvard researchers describe how they link a relatively common MRI probe (superparamagnetic iron oxide nanoparticles) to a short DNA sequence that binds to proteins in cells responsible for brain tissue repair (glia and astrocytes). Then, researchers used the eye drops on mice with conditions that cause “leaks” in the blood-brain barrier. When the animals’ brains were scanned using MRI, brain repair activity was visible. Glia and astrocytes help repair brain and nerve tissue, and have a role in numerous diseases and disorders that cause at least microscopic breaches in the blood-brain barrier, including traumatic brain injury, multiple sclerosis, stroke, cardiac arrest, and glioma, among others. Furthermore, the researchers believe that the probes may also help diagnose thinning of vascular walls in brains, which occurs as Alzheimer’s disease progresses.