High resolution, high field strength MRI studies of the mechanisms and architecture underlying human stereoscopic vision

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Functional magnetic resonance imaging (fMRI) can be used to visualise activity in the brains of human subjects. When a region of the brain becomes active the cells begin to fire action potentials to communicate information. An increased flow of oxygen is required in that local region to fuel this activity. Since oxygenated (fresh) and de-oxygenated blood have different magnetic properties, it is possible to use the ratio of these two substances to measure changes in brain activity. The techniques used for looking at the human brain, both its function and its connections, are constantly evolving, allowing us to gain more and more information.This project is designed to determine how we use our 2 eyes to see in depth. There are many pieces of information that can tell us where objects are in relation to each other, but if a slight difference is introduced between the images of the two eyes artificially, such as in ?Magic Eye? pictures, an object may ?jump? out without any other information available. Using stimuli that are similar to Magic Eye pictures we will investigate 3 main issues:1) We will look in the normal population to see whether different areas of the brain are specialised for processing different stages of depth perception. We will also investigate whether the responses of the brain are related to how good people are at seeing depth. 2) Deficits in depth perception are common, as any misalignment of the two eyes during early childhood due to ?squint? or ?lazy eye? can prevent the development of binocular neurons; those sensitive to input from both eyes. Although these conditions can often be corrected surgically, not all children regain their binocular vision. We will investigate the neural responses in such subjects lacking binocular vision to examine how their brains process information differently from people with normal binocular vision.3) The amount of detail that can be seen with fMRI depends on various factors, but an important one is the strength of the magnet used for the experiments. We are very fortunate in Oxford as we will have access to a very strong magnet that we will use to investigate the very fine organisation believed to underlie the perception of depth.