When a person looks at an object, each eye sees it from a slightly different angle and sends those binocular-based pictures back to the brain. The differences between the two images are integrated into a single one, creating the 3D effect, this phenomenon is known as stereopsis. A puzzle for neuroscience, and robotics, is how insects achieve complex stereopsis with such tiny brains.
Now, a study from researchers at Newcastle University identifies neurons in the insect brain which compute 3D distance and direction. The team states their study not only proves the existence of disparity sensitive or 3D neurons in an insect brain, it also reveals feedback connections previously unknown in any animal species. The opensource study is published in the journal Nature Communications.
Mapping vision in mantises
Previous studies show praying mantids use stereopsis, the computation of distances from disparities between the two retinal images, or 3D vision, to trigger a raptorial strike of their forelegs when prey is within reach, however, the neuronal basis of this ability is entirely unknown. The current study identifies individual neurons in the praying mantis brain which are tuned to specific depth perceptions in the 3D-space.
The current study fits mantises with specially designed 3D glasses and shows them 3D movies of simulated bugs while their brain activity is monitored. When the image of a bug came into striking range for a predatory attack the lab was able to record the activity of individual neurons. The neurons recorded were then stained to reveal their shape which allowed the identification of four classes of neurons involved in mantis stereopsis.
The future of stereoscopic vision
Results show the stained images captured using a powerful microscope reveal the dendritic tree of a nerve cell, where the nerve cell receives inputs from the rest of the brain, enabling 3D behavior.
Data findings show the binocular response fields of several neurons show clear evidence of center-surround mechanisms and are similar to disparity-tuned neurons in the vertebrate visual cortex. The group states these are the first neurons discovered in any invertebrate with properties suitable for supporting stereoscopic vision.
The team surmises they have identified specific neuron types in the brain of an invertebrate which are tuned to locations in the 3D space. For the future, the researchers state they intend to further research into the computation of the relatively simple brain of the praying mantis with the aim of developing simpler algorithms for machine and robot vision.
Source: Newcastle University
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