Monday, December 9, 2013

Language in developmental and acquired disorders

As I mentioned in an earlier post, last June I had the great pleasure and honor of participating in a discussion meeting on Language in Developmental and Acquired Disorders hosted by the Royal Society and organized by Dorothy Bishop, Kate Nation, and Karalyn Patterson. Among the many wonderful things about this meeting was that it brought together people who study similar kinds of language deficit issues but in very different populations -- children with developmental language deficits such as dyslexia and older adults with acquired language deficits such as aphasia. Today, the special issue of Philosophical Transactions of the Royal Society B: Biological Sciences containing articles written by the meeting's speakers was published online (Table of Contents).

Our contribution (Mirman & Britt, 2014) to the discussion and the special issue was a review of acquired lexical "access" deficits. This was a challenging assignment because the very notion of lexical (or semantic) "access" is quite vague and different people use it to mean different things. Nevertheless, there is now a substantial body of evidence that there are at least two different kinds of semantic impairment. The first and more well-understood one is associated with the progressive neurodegenerative syndrome known as "semantic dementia" (also known as the semantic variant of primary progressive aphasia) and thought to be a deficit of the store of semantic knowledge. The second is associated with stroke aphasia and thought to be a deficit of accessing the semantic knowledge. Unfortunately, theoretical development has not quite kept pace with the growth of phenomena attributed to lexical-semantic access deficits (hence the title of our paper: What we talk about when we talk about access deficits).

After much consideration and trial-and-error, we decided that it would be best to organize our review starting with the phenomena. As one of my mentors once said, "the data are always true." Whatever one might think of the theory of "access deficits," we felt that it was indisputable that there were at least two different kinds of deficits, so we decided to put that evidence at the front of our paper. We then turned to the theoretical perspectives that have been proposed, trying to be fair to both their strengths and weaknesses, and concluded with what we see as the major open questions and most promising future directions in this domain.

I have not yet had a chance to read all of the other articles in the special issue, but if they are half as good as the presentations, then this will be a landmark collection of papers for people interested in understanding how language processing breaks down and what that tells us about the cognitive and neural organization of language. Mirman, D, & Britt, A. E. (2014). What we talk about when we talk about access deficits Philosophical Transactions of the Royal Society B: Biological Sciences, 369 (1634).

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