Search results
Results From The WOW.Com Content Network
The visual pathway consists of structures that carry visual information from the retina to the brain.Lesions in that pathway cause a variety of visual field defects. In the visual system of human eye, the visual information processed by retinal photoreceptor cells travel in the following way:
Visual fields tests will delineate chiasmal syndromes because the missing fields will not cross the midline. Junctional scotomas classically show ipsilateral optic disc neuropathy with contralateral superotemporal defects. Bitemporal hemianopia with or without central scotoma is present if the lesions have affected the body of the chiasm. A ...
Lesions in the visual pathway affect vision most often by creating deficits or negative phenomena, such as blindness, visual field deficits or scotomas, decreased visual acuity and color blindness. On occasion, they may also create false visual images, called positive visual phenomena.
Lesions in the optic tract correspond to visual field loss on the left or right half of the vertical midline, also known as homonymous hemianopsia. A lesion in the left optic tract will cause right-sided homonymous hemianopsia, while a lesion in the right optic tract will cause left-sided homonymous hemianopsia.
It creates a bottom-up saliency map of the visual field to guide attention or eye gaze to salient visual locations. [35] [clarification needed] Hence selection of visual input information by attention starts at V1 [36] along the visual pathway. Visual information then flows through a cortical hierarchy. These areas include V2, V3, V4 and area ...
Lesions in the pathway cause a variety of visual field defects. The type of field defect can help localize where the lesion is located (see figure). A lesion in the optic nerve of one eye causes partial or complete loss of vision in the same eye, with an intact field of vision in other eye.
If a lesion only exists in one unilateral division of the optic radiation, the consequence is called quadrantanopia, which implies that only the respective superior or inferior quadrant of the visual field is affected. If both divisions on one side of the brain are affected, the result is a contralateral homonymous hemianopsia.
The cutaneous receptors of the skin project in an orderly fashion to the spinal cord, and from there, via different afferent pathways (dorsal column-medial lemniscus tract and spinothalamic tract), to the ventral posterior nucleus of the thalamus and the primary somatosensory cortex. Again, adjacent areas on the skin are represented by adjacent ...