I am interested in
understanding the production and comprehension of language and how it relates
to other cognitive abilities and certain neurological structures. My research has focused on different
types of aphasic patients and how certain cognitive deficits may contribute to
language difficulties, as well as understanding what role different
neurological structures play in language production or comprehension.
During my time at
Rice University I have investigated the relationship between short-term memory
deficits and language impairments in aphasic patients. Previous research has found that
certain types of short-term memory deficits (i.e., semantic and phonological)
lead to specific language impairments (nonfluent and fluent aphasia,
respectively). It has also been
found that short-term memory deficits are related to damage to specific
neurological structures, with semantic short-term memory deficits being caused
by damage to the left inferior frontal gyrus and phonological short-term memory
deficits being caused by damage to the left supramarginal gyrus.
My own research
has primarily focused on the cognitive mechanisms involved in lexical
retrieval. My first research
project involved testing patients in our lab to see if any of them showed what
has been termed Òrefractory anomia,Ó in which patients have difficulty in
retrieving a lexical item when it is presented in the context of other
semantically related items or at faster rates of presentation. Unlike other nonfluent patients
reported to show refractoriness, our patients have very well-preserved single
word production, so we were interested if any of them would show the same effect
in their response latencies, but not in error rates. For patients and controls, the opposite of the expected
effects were found, with semantically blocked items and items presented at
faster presentation rates being produced more quickly. Subsequent research by another graduate
student found that two nonfluent patients actually did show refractory effects
in their response latencies, but this required repeated naming of the items in
semantically related contexts. One
experiment in my study did however show that a nonfluent patient ML showed
little difference from controls in naming of a single presented item, but
showed greatly exaggerated effects when having to produce two or three items
presented together, indicating problems in lexical retrieval that may be
related to his semantic short-term memory deficit.
I am interested in
more recent findings indicating that semantic short-term memory deficits may
also be related to deficits in executive functioning relating to processing of
verbal material. Related research in
our lab has found that semantic short-term memory deficits may be related to
word-retrieval deficits. I think
that the possibility that semantic short-term memory deficits may be caused by
deficits in verbal control mechanisms is an exciting possibility to explore and
this was the topic of my masterÕs thesis.
More specifically,
my masterÕs thesis examined the relationship between verbal inhibition, lexical
retrieval, and semantic short-term memory. The idea for the thesis started with the observation of some
nonfluent patients in our lab and other patients reported in the literature,
who, although having problems in the production of speech, will nevertheless
unexpectedly produce very low-frequency items, which gives the impression that
the patient is attempting to speak in a very formal or overly precise
manner. In a sentence completion
study I conducted, it was found that patient ML produced very unusual, though
technically correct, completions, and that the completions were significantly
lower in word frequency as compared to controls and other patients tested. The purpose of my masterÕs thesis was
to explore whether the unexpectedly high rate of production of low-frequency
items by patient ML is caused by difficulty in resolving competition between lexical
competitors through the inhibition of lexical items after production.