Abstract:
Language disorders afflict 6 to 8 million people in the United States. One common symptom in language
disorders is difficulty comprehending the grammatical structure of sentences. Understanding that the sentence
“The car at the stoplight is blue” refers to a blue car requires recognizing “at the stoplight” as a distinct phrase
that modifies the preceding noun phrase “the car”. People with grammatical comprehension disorders have
difficulty with this. With intracranial recordings in human neurosurgical patient volunteers with normal
language function we previously described the patterns of phrase-structure building in neural activity observed
in the left inferior frontal gyrus (IFG) and superior temporal sulcus (STS). This is hypothesized to play a causal
role in the comprehension of sentence structure, but such a role has never been demonstrated. Aim 1 will test
this hypothesis by directly electrically stimulating and thus transiently disrupting the left IFG and STS of
neurosurgical patient volunteers at key phrasal boundaries in a sentence and observing how this affects
sentence comprehension accuracy. Aim 2 will investigate a direct link between neural activity and the resulting
behavior for each trial using a self-paced reading task while we record neural activity directly from key
language network sites, specifically the left IFG and STS. We will correlate neural activity with per-word
reaction times, which reflect the processing requirements for each word. Also, for the experiments in Aim 1 we
will simultaneously record activity from one language network area (IFG or STS) while stimulating the other
area to demonstrate how disrupting each area affects activity elsewhere in the language network. Altogether,
we expect that disrupting fronto-temporal phrase-merging activity will reliably create comprehension errors,
and that this neural activity will be tied to behavioral markers of phrase processing and affected by the
intracranial stimulation in a way that we can predict given the result that the stimulation has on behavior. Our
team is uniquely qualified to accomplish these aims. This proposal will provide me with training in the
technique of intracranial stimulation with simultaneous recording in human patient volunteers performing a
task, in deepening my understanding of theoretical linguistics through formal instruction and mentoring, and in
communication disorders, specifically aphasia. In summary, the proposed studies and training plan will lead to
a better understanding of grammatical deficits in language disorders, leading to improved treatments and
interventions, and will expand my impact as a neuroscientist, serving as a bridge to independent funding.