Clinical and Anatomical Evidence for Parallel Processing in the Human Visual System

Classes of retinal ganglion cells have been morphologically and physiologically described in several experimental animals. Whereas no such classification of retinal ganglion cell types has been made in man, there have been psychophysical and retinal electrophysiological human studies suggestive of a similar segregation of retinal ganglion cells into classes which subserve different functions. The neuro-ophthalmic clinician often has psychophysical evidence of the separation of visual functions. For example, it is well known that a patient with optic neuritis may have a pronounced afferent pupillary defect despite having normal visual acuity. Moreover, such a patient may measure best for Snellen visual acuities when the contrast is neither too high nor too low. Indeed, we offer evidence that brightness-sense is a sensitive measure of optic nerve disease which may be singularly impaired. Thus we see that several diseases of the optic nerve produce impairments of function which are out of proportion to other defects of ViSiOn. This mismatch between certain parameters of function by ophthalmic diseases has major clinical and scientific implications

Radiological/Surgical Anatomy of the Skill Base: A Neuro-Ophthalmological Perspective

Comprehensive books and numerous articles have examined the skull base from a variety of perspectives. While obviously the anatomy of the skull base has not changed, several developments both in the nature of subspecialties and in technology have required new interpretations and applications of anatomical principles. Whereas in the past, separate books describing the anatomy of the skull base were made available for the neurosurgeon, the ear\nose\throat surgeon, the neuro-radiologist, and occasionally the neuro-ophthalmologist, rarely has the base of the skull been looked at from a unified point of view

Primary Optic Nerve Pathways

In general, parallel processing refers to separate channels through which information can be independently processed. Consider the US Post Office as an example of parallel processing. Letters to one office have no effect on letters to another. Vision scientists have considered parallel processing in the visual system of a variety of animals for many years. However, ophthalmologists and other clinicians have tended to see the human visual system as serial processing. Textbooks still describe how the visual information proceeds from retina to the lateral geniculate nucleus (LGN) via the optic nerve then ""relays"" from the LGN to the visual cortex via the optic radiations. We hope that in the future textbooks will take Into account the greater complexity of visual information processing