5 - Extensions of connectionism

Summary

The work of Wernicke, Lichtheim, and many other late nineteenth-century investigators dealt mainly with the various parts of what may be termed the “faculty for language”. The identification of elementary components of this faculty, the delineation of interactions of components, and the search for the neural loci of these components and their connecting pathways, was much debated in the neurological literature of that period. Although there were many variations of these models, those we have discussed in the previous chapter are quite typical of the work in this tradition. We shall not review all this work, which would be far beyond the scope of an introductory text (we cannot devote all our text to the last century), but we will consider one more analysis very much in keeping with the connectionist approach, Dejerine's analysis of the syndrome of alexia-without-agraphia. The example is chosen with malice aforethought. It serves as a natural bridge to the approaches to the agnosias and apraxias undertaken within the connectionist framework, which we shall mention briefly; and, having considered its nineteenth-century description, we will be able to appreciate a twentieth-century refinement of views regarding this syndrome later in this chapter. In Chapter 14, we shall reconsider this syndrome from a psycholinguistic viewpoint.

In 1892, Jules Dejerine published the case history and neuropathological autopsy findings of a patient with a striking set of difficulties. Dejerine's patient was an engineer who had suffered a stroke which left him unable to read words, sentences, or letters. He was unable to see in the right visual half-field. He was unable to name colors. He had been a talented amateur musician, able to sight-read music, and he had lost this ability.