Using an fMRI machine fitted with a stereoscopic projection system, researchers at the University of Texas at Austin identified the region of the brain responsible for working out the 3D nature of what the eyes are seeing. The area, known as MT+, is located right behind the ears.
For the study, Huk and his colleagues had people watch 3-D visualizations while lying motionless for one or two hours in an MRI scanner fitted with a customized stereovision projection system.
The fMRI scans revealed that the MT+ area had intense neural activity when participants perceived objects (in this case, small dots) moving toward and away from their eyes. Colorized images of participants’ brains show the MT+ area awash in bright blue.
The tests also revealed how the MT+ area processes 3-D motion: it simultaneously encodes two types of cues coming from moving objects.
There is a mismatch between what the left and right eyes see. This is called binocular disparity. (When you alternate between closing your left and right eye, objects appear to jump back and forth.)
For a moving object, the brain calculates the change in this mismatch over time.
Simultaneously, an object speeding directly toward the eyes will move across the left eye’s retina from right to left and the right eye’s retina from left to right.
“The brain is using both of these ways to add 3-D motion up,” says Huk. “It’s seeing a change in position over time, and it’s seeing opposite motions falling on the two retinas.”
That processing comes together in the MT+ area.
Here’s one of the researchers explaining what the brain does when it activates its 3D processing area:
Image: Dr Bas Rokers and an enhanced image of his brain from an fMRI scan that shows the MT+ area active when perceiving 3-D motion (bright blue area in the lower left of the photo).
Full story @ University of Texas at Austin: Brain’s Center for Perceiving 3-D Motion Is Identified…
(hat tip: The Engineer Online)