Ever close your eyes and have an image burned into your retina? Our brains may do the same thing after we die.
Scientists have developed a technique that can recreate a 3D map of the cells that were firing in a mouse’s brain a few hours before it died, giving them a high-resolution picture of what was going on in the mouse’s head during life—in this case, when it met a member of the opposite sex. The team of researchers published their results yesterday in the journal Cell Reports.
“The work mapping these circuits in the whole mouse brain is quite heroic,” wrote Rafael Yuste in an email. Yuste, professor of biological sciences and neuroscience at Columbia University and a leader of the Brain Activity Map Project that inspired Obama’s BRAIN initiative, was not involved in the study. He cautions that it’s a less than ideal technique since the mouse must be sacrificed in the process—mice won’t sit still long enough for a noninvasive MRI scan.
“We can take normal mice and have them do complex tasks such as social behavior, and then look throughout the whole brain and identify brain regions that were activated—at cellular resolution,” said Pavel Osten, professor at Cold Spring Harbor Laboratory and the senior investigator on the study.
Using mice modified so their neurons glow green when they fire, the researchers found that, even before any mating or aggression behaviors, the brain regions associated with reproductive behavior, sexual behavior, and aggression light up when a male mouse meets a female mouse. But when a male mouse meets another male mouse, brain regions that control defensive behavior—in addition to the ones that control sexual behavior and aggression—glow.
Osten’s new methodology, which improves on one he originally published in 2012, automates several different laboratory techniques formerly done by hand, which in this study allowed the researchers to create a map of brain activation from the earliest moments of sensing another animal to the sex-specific behavioral inclinations that evoked. He hopes that it will eventually be able to shed light on how diseases and pharmaceuticals change connections in the brain. Until now, Osten said, “That comparison in animals hasn’t really been possible at all at this kind of unbiased scale.”
Yuste wrote that detecting fluorescent markers of brain activity after death represents “a step towards future techniques for the full blown mapping of neuronal activity in living brains in real time.”
Photo credit: Frances S. Chance/Janelia Farm Research Campus/HHMI/Sandia National Laboratory