Discoveries

Salk researchers have resolved a long-standing scientific debate about how behavior is organized in the brain. Associate Professor Xin Jin and first author Claire Geddes, a UC San Diego graduate student, discovered that learned behavior is organized in a hierarchy with multiple levels of control, offering possible new therapeutic targets for disorders that involve an inability to control one’s actions. The study used mice trained to carry out a series of lever presses in a specific order, left-left-right-right, to make the discovery.

A Salk team led by Associate Professor Nicola Allen and first author Elena Blanco-Suarez showed that astrocytes—long-overlooked supportive cells in the brain—enable the brain’s plasticity, a previously unknown role for these cells. The team found that a protein secreted by astrocytes called Chrdl1 increases the number and maturity of connections between nerve cells, enabling the stabilization of neural connections and circuits once the connections finish developing. The findings could point to ways to restore connections lost due to aging or trauma.

Professor Satchin Panda, first author Ludovic Mure and colleagues pinpointed how certain cells in our eyes process ambient light and reset our internal clocks, or circadian rhythms—the daily cycles of physiological processes. When these cells are exposed to artificial light late into the night, our internal clocks can become disoriented, resulting in a host of health issues. By detailing the interactions of the light-sensitive protein melanopsin and how the eyes react to light, the research may lead to new treatments for migraines, insomnia, jet lag and circadian-rhythm disorders.

For decades, scientists studying the visual system thought that neurons operated as filters. Some neurons preferred coarse details of the visual scene and ignored fine details, while other neurons did the opposite. Professor Thomas Albright, first author Ambarish Pawar and coauthors found that the same neurons that preferred coarse details were able to change to prefer finer details under different conditions. The work could help to better understand neural mechanisms that shape our perceptions of the world.