Auditory comprehension of language is fundamental to human communication and is often disrupted in neurological disorders for reasons that are incompletely understood. The overarching goal of the proposal is to understand the neural basis of auditory language comprehension and therefore open the door to effective interventions. We use complementary lesion/stroke-based and functional MRI methods to address three specific aims.
Aim 1 : Understand the neural basis of speech perception. The idea that the motor system may play a prominent role in speech perception has gained much popularity. We have argued instead that speech perception is bilaterally organized in the superior temporal lobes with minimal frontal/motor modulation. Experiments proposed under this aim test these competing ideas using both comprehension and syllable discrimination tasks and signal detection methods.
Aim 2 : Understand the role of extra-auditory influences on speech perception/comprehension. Speech perception is influenced by contextual information. Here we examine the influence of two cues, visual speech and word-level information. We hypothesize that temporal lobe circuits are primarily responsible for both of these sources of influence on speech perception. Our proposed studies will test this hypothesis.
Aim 3 : Understand the neural basis of sentence-level processing. Speech perception and word comprehension are critical for comprehension, but effective communication relies additionally on higher-order processes such as those involved in sentence comprehension. We propose studies aimed at testing our hypothesis that anterior temporal regions are particularly important for integrating lexical and syntactic information to derive sentence meaning. Methodologically, this program is driven by a commitment to the view that multiple methods are required for deriving a complete picture of a neural process. To speed the pace of lesion work, which can be laboriously slow, we have developed a Multisite Aphasia Research Consortium (MARC) that will enable us to collect data at an unprecedented pace. This will remove a critical barrier to rapid progress by quickly accruing the large samples needed for quantitative lesion-behavior correlation analyses.
Language disorders affect millions of people in the United States, and deficits in comprehending speech are a prominent component of many of these disorders. By studying the basis for auditory comprehension deficits in brain injury and by mapping these systems in healthy adults we will gain a more complete understanding of what going wrong, leading to more targeted therapeutic approaches to treatment of language dysfunction. !
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