Neuroscience

Edward Callaway’s lab has developed a new reagent to map the brain’s complex network of connections that is 20 times more efficient than their previous version. This tool, detailed by first author Euiseok Kim in Cell Reports in April 2016, improves upon a technique called rabies virus tracing, which was originally developed by Callaway and is commonly used to map neural connections.

This dramatic improvement will help researchers illuminate aspects of brain disorders where connectivity and global processing goes awry, such as in autism, schizophrenia and some motor and neurodevelopmental diseases.

A microscope about the size of a penny is giving scientists a new window into the everyday activity of cells within the spinal cord. The new miniaturized imaging methods, described on April 28, 2016 in Nature Communications, reveal more about nervous system function and could lead to pain treatments for spinal cord injuries, chronic itch and diseases such as amyotrophic lateral sclerosis (ALS).

Salk Institute scientists showed how an FDA-approved drug boosts the health of brain cells by limiting their energy use. Like removing unnecessary lighting from a financially strapped household to save on electricity bills, the drug—called rapamycin—prolongs the survival of diseased neurons by forcing them to reduce protein production to conserve cellular energy.

Rapamycin has been shown to extend lifespan and reduce symptoms in a broad range of diseases and, at the cellular level, is known to slow down the rate at which proteins are made.

But the new Salk research, led by Salk Professor Tony Hunter and published in the journal eLife, suggests that rapamycin could also target the neural damage associated with Leigh syndrome, a rare genetic disease, and potentially other forms of neurodegeneration as well.

When tweaking its architecture, the adult brain works like a sculptor— starting with more than it needs so it can carve away the excess to achieve an ideal design. That’s the conclusion of a new study that tracked developing cells in an adult mouse brain in real time.

New brain cells began with a period of overgrowth before the brain pruned back its connections. The observation, described May 2016 in Nature Neuroscience, suggests that novel cells in the adult brain have more in common with those in the embryonic brain than scientists previously thought.

While most of the brain’s billions of cells are formed before birth, Salk Professor Rusty Gage and others previously showed that in a few select areas of the mammalian brain, stem cells develop into new neurons during adulthood. In this study, his group focused on cells in the dentate gyrus, an area thought to be responsible for the formation of memories.

Gage and first author Tiago Gonçalves followed—on a daily basis—the growth of neurons over several weeks. When mice were housed in environments with lots of stimuli, the new cells grew quickly, sending out dozens of branches called dendrites which receive electrical signals from surrounding neurons. When kept in empty housing, new neurons grew slightly slower and sent out less dendrites. But, in both cases, the new dendrites began to be pruned back.

Defects in the dendrites of neurons have been linked to brain disorders like schizophrenia, Alzheimer’s, epilepsy and autism. Charting how the brain shapes these branches—both during embryonic development and in adulthood—may be the key to understanding mental health.

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