Tiny glasses help reveal how praying mantises can see in 3-D

Newfound nerve cells in the insects’ brains play a role in depth perception

praying mantis

LIFE IN 3-D  Colored filters let a praying mantis watch a 3-D video of a moving disk while researchers studied the nerve cells that contribute to the insect’s depth perception.

Newcastle Univ., UK

A praying mantis depends on precision targeting when hunting insects. Now, scientists have identified nerve cells that help calculate the depth perception required for these predators’ surgical strikes.

In addition to providing clues about insect vision, the principles of these cells’ behavior, described June 28 in Nature Communications, may also lead to advances in robot vision or other automated systems.

So far, praying mantises are the only insects known to be able to see in 3-D.  In the new study, neuroscientist Ronny Rosner of Newcastle University in England and colleagues used a tiny theater that played praying mantises’ favorite films — moving disks that mimic bugs. The disks appeared in three dimensions because the insects’ eyes were covered with different colored filters, creating minuscule 3-D glasses.

As a praying mantis watched the films, electrodes monitored the behavior of individual nerve cells in the optic lobe, a brain structure responsible for many aspects of vision. There, researchers found four types of nerve cells that seem to help merge the two different views from each eye into a complete 3-D picture, a skill that human vision cells use to sense depth, too.

SPOT IT In the optic lobe of a praying mantis’s brain, this nerve cell, called a TAOpro neuron, has three elaborate fan-shaped bundles (two shown with a colored stain) that receive incoming visual information. This cell helps compute objects’ depths from information from the insect’s eyes. Newcastle University, UK

One cell type called a TAOpro neuron possesses three elaborate, fan-shaped bundles that receive incoming visual information. Along with the three other cell types, TAOpro neurons are active when each eye’s view of an object is different, a mismatch that’s needed for depth perception.  

The details of the various types of nerve cells, and how they might receive, combine and send visual information, suggest that these insects’ vision may be more sophisticated than some scientists had thought, the team writes. And the principles guiding praying mantis depth perception may be useful to researchers working on improving machine vision, perhaps allowing artificial systems to better sense the depths of objects.   

Laura Sanders is the neuroscience writer. She holds a Ph.D. in molecular biology from the University of Southern California.

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