13 - Formulaic Sequences in Aphasia: A Model

Summary

Introduction

In this chapter we shall explore the consequences of incorporating the formulaic features of aphasic language into a lexical model. In the models developed so far in this book, it has been possible to speak of a single lexicon containing units of different sizes, namely, morphemes, formulaic words and formulaic word strings. Now, however, it seems that it will be necessary to make finer distinctions, both because of what all aphasias have in common and because of the ways they differ.

As we have seen, formulaic word strings are strikingly resilient to most types of aphasia, but, as with single words (mono- and polymorphemic), not all types are equally spared, either within an individual's repertoire or from one patient to another. This seems to suggest that the lexicon needs to be divided in some way other than by unit complexity, so that subsets of words and longer strings can be lost, or spared, together. These different parts of the lexicon would need to be managed from different locations in the brain. Physical distance between operational centres does not necessarily need to be represented in terms of separate components in an abstract processing model. However, if such physical separation influences the pattern of deficits after localized brain damage, then it certainly does need to be modelled in some way.