Visual Information Essay -- Anatomy, The Retina

Visual information is seen because light passes through the cornea and is focused by the lens as an inverted image on the retina (Ellis, 2004). The retina is composed of photoreceptor cells; rods and cones with the greatest density of cones situated within the fovea, thus vision is sharpest for images and information projected to the fovea (Ellis, 2004). Subsequently visual information of lateralized foveal stimuli projects to the cerebral hemisphere within the brain. In the brain, the left visual hemifield projects to the right hemisphere and the right visual hemifield projects to the left hemisphere (Lavidor, Ellis, Shillcock & Bland, 2001). Generally for most individuals (in particular right handed), visual recognition of words and information is more efficient for display within the right visual field. However it is debated whether foveal information lateralized within the left or right visual field is double-projected to both hemispheres or unilaterally projected to the contrala teral hemisphere because the fovea is anatomically split and there is differential contribution of the two hemiretinae. Two theories have been put forward regarding how visual information is projected to the hemispheres. According to the split fovea theory, hemispheric division in processes occurs right up to the point of fixation. When the eyes are fixated within a written word visual information about the letters falling to the left of fixation initially projects to the right cerebral hemisphere, whilst visual information about the letters falling to the right of fixation project to the left cerebral hemisphere. Foveal processing is split so precisely at the vertical midline that all letters at either side of fixation project (unilaterally) to th... ...occurring in foveal vision away from the midline however this is not visible or obvious when recognition of visual information occurs. There is an overlap at the centre of the fovea where information projects simultaneously to both hemispheres, this being consistent with the bilateral theory. On the other hand, split fovea theory is an interesting theory of fixation effects that has been inspired by previous research unconnected with split fovea theory and thus incapable of providing appropriate evidence. More recently, split fovea theory has been based on experiments conducted specifically in its support but in which fixation locations were not monitored and stimuli exceeded foveal vision. It is good to see that research in the area is beginning to improve but it is difficult to be enthusiastic about any theory when there is no compelling evidence to support it.