A case of dyslexia : a peculiar form of word-blindness / by James Hinshelwood.

  • Hinshelwood, James, 1859-1919.
Date:
1896
Catalogue details

Licence: Public Domain Mark

Credit: A case of dyslexia : a peculiar form of word-blindness / by James Hinshelwood. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    ]2 streets of his own city. This form of visual memory supplies us with a kind of mental picture chart, which enables us to find our way with unerring precision amongst scenes and places with which we are familiar. In the case reported by Dr. Wilbrand, and already referred to, this loss of memory for places was a striking symptom, and in my last paper some excellent examples of this form of failure of the visual memory were quoted. Here, then, we have the history of a patient who could not read, who could no longer do his work as a tailor, and who occasionally lost his way in the midst of familiar sur- roundings. Yet the ocular part of the visual mechanism was perfectly normal, and as his visual fields were normal we may also infer that the visual perceptive centres occupying the occipital lobes were also intact. I think it is clear from our analysis of the case that all the symptoms manifested have this very direct relationship to one another—that they are all dependent upon failure of the visual memory. The intelligent exercise of vision is a very complex act of which we have as yet only very imperfect knowledge. To the successful exercise of the function the brain contributes as largely as the eye. The ocular defects in all their multi- tudinous variety have been studied for many years with great industry and success, but the cerebral disorders, which inter- fere with intelligent vision, have until recent years not met with the attention they merit. Increasing knowledge of the cerebral derangements of vision, based on clinical and pathological observation, makes it clear that we must carefully distinguish between the visual perceptive centre and the visual memory centre. The perceptive centres situated in the occipital lobes, chiefiy in the neighbourhood of the cuneus and calcarine fissure, enable us to have conscious perception of objects as occupying a definite position in the visual fields. Derange- ments of this visual centre are evidenced by defects in the visual field, which have all been carefully studied. But the act of vision is infinitely more complex than the simple perception of an object as occupying a particular position in the visual field. It involves complex judgments and, above all, a constant comparison of present visual impres- sions with the vast series of past visual impressions, the accumulated riches of our life experience which are stored up in a spe<^.ial cerebral area, the visual memory centre.