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Brain Clears the Way for Binocular Vision Even Before Eyes are Open

Selective pruning of key brain connections brings two-eyed vision into focus
December 7, 2020
Microscopy image showing cells in red and green

Having too many chandelier cells (red) in the binocular region of the brain can severely impair a mouse's depth perception. Scientists found these branched neurons, which are potent inhibitors, are naturally reduced within the first couple of weeks of a mouse's life, particularly in a subregion of the visual cortex that processes visual information from both eyes (green). The image shows a brain section of a two-week old mouse pup with normal levels of chandelier cells in their visual cortex. Image credit: Bor-Shuen Wang, Huang Lab.

To prepare the brain for binocular vision and depth perception, first you have to take out some of the chandeliers.

That’s the takeaway from a group of neurobiologists from Duke University School of Medicine and Cold Spring Harbor Laboratory, who studied the development of binocular vision in the mouse brain. They discovered that chandelier cells, so-named because they have many long extensions that control the firing of hundreds of excitatory pyramidal neurons and resemble a chandelier light fixture, are selectively removed from the developing mouse visual cortex even before the animal’s eyes are open by a process of programmed cell death called apoptosis.

This pruning of about half of the chandelier cells in the second week of development probably clears a path for certain pyramidal neurons to be more active, since chandeliers tend to have a dampening effect on their excitability, explained Josh Huang, a professor of neurobiology in the Duke University School of Medicine. He led this research at his previous position in Cold Spring Harbor Laboratory on Long Island, spearheaded by postdoctoral fellow Bor-Shuen Wang.