Brain Functions: Visuo-Spatial Skills
This group of cognitive functions analyzes and understands space (i.e., the world around you) in two and three dimensions. They include mental imagery and navigation, distance and depth perception, and visuo-spatial construction. Visuo-spatial functions represent the brain's highest level of visual processing, and requires the proper functioning of your parietal cortex, in the upper part of the brain.
You use mental imagery and navigation to process and rotate 2-D and 3-D objects in your mind, or to virtually move throughout an image from your surroundings which you've reconstructed in your mind. This function is very useful in everyday life -- for example, it allows you to give someone directions to your house by following the route in your mind's eye.
Your visuo-spatial functions also enable you to estimate distance and depth. This lets you move without bumping into any of the obstacles in your path, or to judge whether you have enough time to cross an intersection before an oncoming car reaches you or before the light turns red.
Finally, visuo-spatial construction processes enable you to reproduce drawings or use components to construct objects or shapes. That comes in handy, for example, in solving 3D puzzles or glueing the pieces of a broken vase back together again.
Certain phenomena that occur following a brain injury are disturbing but very striking. One is called unilateral or hemispatial neglect, generally following an injury to the rear portion of the parietal cortex, on the right side of the brain. It's a serious spatial perception disorder generally involving the side of the visual field opposite to where the injury occurs. People suffering from this type of injury on the left, for example, ignore their right field of vision, even to the point where they will only eat the food on the right side of their plate. A man will only shave the left side of his face, or fail to react when a physician pinches his right arm. Some patients might not even recognize their right legs as being their own!
Studies suggest that on average men have better visuo-spatial skills than women; in fact, men and women don't use exactly the same parts of their brains to solve problems requiring 3D image rotation or mental navigation in a virtual environment. The reason for this isn't yet known, but some researchers theorize that evolution and differences in our ancestors' lifestyles are responsible, while others believe sex hormones have a different influence on parts of the brain involved in visuo-spatial tasks. Don't get too worked up about this -- these findings only represent an average and don't apply to everybody. You should also keep in mind that visuo-spatial skills are among those that benefit the most from training.