Three-dimensional perception in monkeys can be influenced, study finds

Stereo-vision is a form of three-dimensional (3D) perception that relies on the binocular disparities originating from the slightly different projections of the world onto the retina of each eye -- the same principle behind 3D movies and television. Until now, the question of how and where cells in the brain control depth perception remained unanswered. Identifying the correct neurons among the brain's billions of nerve cells is like searching for a needle in a haystack.

Previous studies by KU Leuven's Laboratory for Neuro- and Psychophysiology had already demonstrated that the temporal lobe (the part of the brain affecting sleep) can play a role in the stereo-vision of monkeys, whose sight system is very similar to that of humans. The brain cells in the temporal lobe of monkeys have a preference for certain 3D shapes. Some brain cells become more active at the sight of convex 3D shapes, such as cones, while others are excited by concave 3D shapes.

Humans and monkeys

Recent research now shows for the first time a causal link between the activity of these cells and depth perception. The monkeys were trained to distinguish between concave and convex 3D shapes. While the monkeys decided whether a 3D structure was concave or convex, specific cells in their temporal lobe were stimulated with small, short electrical pulses. When brain cells with a preference for convex 3D shapes were stimulated, the monkeys perceived convex shapes -- even if the object before them was concave.

Using brain scans, a region in the human brain was recently discovered that may correspond to the area in the temporal lobe of the monkey. The research on monkeys suggests that the corresponding area in the human brain also plays an important role in 3D perception and that brain manipulations may someday be of benefit for people with visual impairments.