Ocular Dominance Columns
The visual system is the most well-studied sensory system of animals. From these studies it is known that processing vision within the brain is extremely complex. Part of this processing occurs within ocular dominance columns. Ocular dominance columns are groups of neurons that span several layers of the primary visual cortex. They are anatomical structures that make up the striate cortex, which is a portion of the primary visual cortex. Ocular dominance columns are found as a striped pattern on the surface of the striate cortex. They are perpendicular to another set of cells that make up the orientation columns. Drs. David H. Hubel (1926—2013) and Torsten N. Wiesel (1924—) discovered ocular dominance columns during their research in the primary visual cortices of cats. Since these experiments, ocular dominance columns have been found in many mammals, including humans.
Dominant Eye Test
Humans do not only have a dominant hand (right or left), but also have a dominant eye. This develops during childhood and has a critical period for development. The medical term for dominant eye is ocular dominance. It means that one eye is preferred for visual input over the other eye. Ocular dominance may not be on the same side as the person’s dominant hand. This is because both the left and right hemispheres of the brain control vision as well as control different halves of the visual field and of each retina (the back of the eye where objects are visually formed). Just as most humans are right-handed, most are also right-eye dominant.
2 eyes (for one of the tests below, the person must have the ability to close one eye at a time)
2 hands, forming a triangle shape
An object in the distance (about 10 feet away)
There are two easy ways to determine a person’s dominant eye. Both tests start with having the person hold their arms out at eye level. Next have the person make the letter “L” with each hand. Specifically, have the person hold their palms outward, fingers up, and thumbs out—making the L-shape. Have the person bring their hands together and cross one over the other. This makes a triangle space: one thumb over the other and one set of fingers over the other. Next, have the person look through the triangle space made by their hands at an object with both eyes. It is preferable to have the entire object almost completely fill the space. The person will use these directions to complete both tests to determine which eye is dominant.
Test 1: Keeping the hands together, have the person bring their hands back to their face toward one eye. For example, the person will bring their triangle-shaped hands to their right eye until the base of their left thumb touches the tip of their nose. If the image stays within the open space, that is the person’s dominant eye. Now have the person start over and bring their hands back to the left eye until the base of their right thumb touches their nose. The object should partially or completely disappear from the opening.
Test 2: Keeping the hands together, have the person close one eye and then the other. If the image stays within the open space, that is the person’s dominant eye. The object will seem to “jump” sideways when the dominant eye is closed. To learn more about your dominant eye please see http://www.sciencemadesimple.co.uk/activities/left_or_right_eyed
Jennifer L. Hellier
Anatomy and Physiology
When an object is viewed, its image is sent to the retina of the eye and then through the optic nerve to the lateral geniculate nucleus of the thalamus. Here the image’s information is sent to the primary visual cortex, where the ocular dominance columns are located. These columns are alternating bands and patches from the left and right eye preferences. Previously, it was thought that ocular dominance columns are like an orderly sensory map of the outside world that develop by activity-dependent processes. However, more recently, it has been shown that ocular dominance columns develop earlier than originally thought and that they have a predetermined specification pattern.
These columns are activated primarily from the input of one eye and not the other and they develop in utero. However, after birth there is a “critical period,” which is now called the “sensitive period,” for ocular dominance columns. Visual input from both eyes is required for developing vision. However, after a baby is born, it is crucial that both of the baby’s eyes have visual input, as the columns undergo activity-dependent plasticity. This means the ocular dominance columns can degrade during the sensitive period. Hubel and Wiesel found that blocking vision in one eye during the critical period resulted in the unaffected eye developing ocular columns in regions of the striate cortex that would normally be developed by the blocked eye.
Originally, ocular dominance columns were hypothesized to be important for binocular vision. However, these columns are not as distinct or well developed in all animals with binocular vision, such as rats and squirrel monkeys. Now, scientists are wondering if ocular dominance columns are more a result of development, particularly from synaptic plasticity or Hebbian learning. These functions can occur from the spontaneous activity of the retina of the developing fetus or from the lateral geniculate nucleus of the thalamus that projects to the striate cortex. Other studies, however, suggest that ocular dominance columns may be just a result from visual development and may not have a true function.
Jennifer L. Hellier
See also: Blindness; Hubel, David H.; Optic Nerve; Visual Fields; Visual Perception; Visual System; Wiesel, Torsten N.
Adams, Daniel L., Lawrence C. Sincich, & Jonathan C. Horton. (2007). Complete pattern of ocular dominance columns in human primary visual cortex. Journal of Neuroscience, 27, 10391—10403.
Purves, Dale, et al. (2008). Neuroscience (4th ed.). Sunderland, MA: Sinauer Associates.
Tomita, Koichi, Max Sperling, Sidney B. Cambridge, Tobias Bonhoeffer, & Mark Hübener. (2013). A molecular correlate of ocular dominance columns in the developing mammalian visual cortex. Cerebral Cortex, 23(11), 2531—2541. http://dx.doi.org/10.1093/cercor/bhs232. Retrieved from http://cercor.oxfordjournals.org/content/23/11/2531.long