Alexica and Agnosia, Prosopagnisia, Strabismis and Stereopis headlne in neurologist Oliver Sack's latest offering, The Mind's Eye, on rare and fascinating brain behaviors. As usual, he has written a fascinating volume of lesions and plasticity.
However, since these essays are centered around case studies, the book is accessible to a general audience that might be lacking in medical, scientific and Latinate background. Interestingly, such people are rarely included in his cases; most people discussed seem to be accomplished artists or people with medical degrees.
The book open with three case studies, a concert pianist, an artist, and an author, all with variations of alexia (the inability to recognize words) and agnosia (the inability to recognize objects). These are all cases where eye sight - lens, retina, optic nerve, etc. - is fully intact and the problem is traceable (with brain imaging: CAT scans and fMRI) to some brain abnormality, such as PCA - posterior cortical atrophy. As might be expected the book is long on Latin descriptions with a few causes (stroke) and no real mechanisms.
Brain science has made tremendous progress through the use of brain imaging which means scientists no longer have to wait for the patient to die to see what is happening. While some areas of the brain have been identified, progress is hampered by two poorly understood phenomena.
The first is variability: human behavior and abilities vary widely, and these case studies seem to include those beyond the 3-sigma range - certainly no place to find principles to apply to the general population.
The second is the near mystical term: plasticity. Brain science is torn between innate and acquired abilities. When a lesion consistently causes the same deficit (alexia) or an ability seems to be in place from birth (facial recognition), the scientists talk of innate structures. However, when someone recovers from serious brain damage or overcomes blindness or deafness, plasticity reigns supreme.
In some cases, both are intermixed to explain some difficult conundrum. The most interesting example of this is alexia. There is clearly an area of the brain consistently responsible for word recognition. But how can this be when word recognition is too recent to have any impact on evolution. Based on this problem, Wallace, the other discoverer of evolution, declared this to be proof of God's hand in the creation of humans.
The unconvincing scientific argument is that the brain has innate pattern recognition - the (dubious) support for this is that some computer program declared that all alphabets/characters share common characteristics (hopefully) determined by these innate brain structure and everything else associated with reading is plasticity. Scientifically this is an improvement on "the hand of God," but still need some research.
A wonderful book of odd diseases and science; only marred by a long chapter transcribed from the author's journal which is missing much needed composition and editing. A chapter easily skipped.
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