Abnormalities of language comprehension characterize many neurodevelopmental and acquired disorders, leading to severe social communicative dysfunction. Many of these same disorders are also characterized by executive deficits of cognitive control, such as conflict resolution, selection, monitoring and adaptation. Yt we know little about the basic relationships between language processing and cognitive control. This grant uses multimodal neuroimaging techniques to ask how, when and where the neural systems mediating language comprehension and cognitive control interact in healthy adults. Our basic hypothesis is that we use context whenever we can to predict upcoming information at multiple levels of representation, and that, when an incoming word disconfirms some or all of our prior prediction(s), we engage in prolonged attempts to integrate that word into its context. We further hypothesize that the neural mechanisms mediating this prolonged integration are closely linked to core mechanisms of cognitive control, and that they depend on both the strength/certainty as well as the nature of our prior predictions (lexical vs. event structure). Finally, we hypothesize that they play an essential role in enabling us to rapidly and flexibly adapt our comprehension mechanisms to the ever-changing demands of our overall communicative environment. To test these hypotheses, we propose a series of experiments that systematically manipulate both the constraint and the nature of linguistic context, and we use three complementary neuroimaging techniques--event-related potentials (ERPs), functional MRI (fMRI) and magneto-encephalography (MEG)--to probe the temporal and spatial patterns of brain activity recruited to incoming words in these contexts.
Under Aim 1, we probe the neural mechanisms that detect and resolve conflict between a strong, high certainty prediction and an incoming word that violates this prediction.
Under Aim 2, we probe the neural mechanisms that select an incoming word that matches a medium certainty prediction and suppress alternative competing prediction(s).
Under Aim 3, we ask whether different individuals can use the same context to predict with different strengths/certainties, leading some people to mount a high conflict neural response (see Aim 1), and others to mount a selection neural response (see Aim 2) to integrate the same linguistic input. We also ask whether these individual differences can be linked to behavioral performance and brain activity associated with executive tasks that tap into more general conflict control mechanisms (Stroop; AX-CPT). Finally, under Aim 4, we ask whether the same individuals can adapt to their wider communicative environment by predicting with different strengths/certainties, leading them to engage different neural mechanisms (a high conflict or a selection response) to integrate the same word into the same local contexts. By addressing these questions, this project will identify core neural mechanisms that can break down and lead to comprehension deficits in multiple different disorders. It therefore lays the foundation for the development of targeted, theoretically motivated neurocognitive strategies to prevent and improve communication deficits in these disorders.
Language comprehension is necessary for effective human communication and social function. Therefore, when it breaks down, as it does in many neurodevelopmental and acquired disorders, the consequences can be devastating. This grant uses multimodal neuroimaging techniques to ask fundamental questions about the neural mechanisms mediating language comprehension in healthy adults, laying essential groundwork for the development of theoretically motivated prevention and remediation strategies to target specific communication deficits across multiple disorders.
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