Research Report: Uncovering brain’s underlying circuit architecture

Research-Report-Lynne-Friedmann-WebBy Lynne Friedmann

The power of the brain lies in trillions of synapses — intercellular connections that together form complex neural networks. Efforts to map these individual connections to see how they influence specific brain functions have so far been unsuccessful. Now, scientists at the Salk Institute and the Gladstone Institutes (San Francisco) have found a way to untangle these networks using an innovative brain-tracing technique.

The technique, known as the “monosynaptic rabies virus system,” assembles brain-wide maps of neurons that connect with the basal ganglia, a region of the brain involved in movement and decision-making.

The system uses a modified version of the rabies virus to “infect” a brain region, which in turn targets neurons that are connected to it. In the current study, when the system was applied in genetic mouse models the team could see how sensory, motor and reward structures in the brain connected to neurons in the basal ganglia.

Using the rabies virus system to pinpoint distinct network disruptions in distinct types of disease could significantly improve understanding of underlying molecular mechanisms.

— Finding appears in the journal Neuron. News release at

• Potential biomarker for cancer diagnosis.

As a result of a glitch in cell division, entire chromosomes can sometimes end up outside the nucleus. Known as micronuclei, scientists studying cancer development have known about them for some time because they are associated with specific forms of cancer and are predictive of a poor prognosis.

A team of scientists at the Salk Institute for Biological Studies report that disrupted micronuclei, which can trigger massive DNA damage on chromosomes, might play an even more active role in initiating cancer than previously thought.

The study showed that more than 60 percent of micronuclei undergo catastrophic dysfunction in solid tumors such as non-small cell lung cancer. This suggests that micronuclei could be a valuable biomarker for diagnosis of solid tumors.

— Findings are published in the journal Cell. News release at

Lynne Friedmann is a science writer based in Solana Beach.