Linguistics Colloquium: Idan Asher Blank
Idan Asher Blank, MIT
Title: The functional architecture of language comprehension mechanisms: fundamental principles revealed with fMRI
Abstract: A key requirement from cognitive models of language comprehension is that they specify the distinct computational mechanisms that are engaged in language processing and the division of linguistic labor across them. Here, I address this requirement from a cognitive neuroscience perspective by employing functional MRI to study the neural implementation of comprehension processes. My experimental approach, unique in studies of language, employs a novel combination of methods to simultaneously achieve (i) increased functional resolution, via localization of functional brain regions at the single-participant level and explicit comparisons of their respective functional profiles; (ii) ecological validity, through data-driven, model-free paradigms using naturalistic stimuli; and (iii) replicability across stimuli, samples and paradigms.
Using this approach, I focus on two cortical networks engaged in comprehension: one, the “high-level language network”, is selectively recruited by linguistic processing but not by other cognitive functions; another, the “multiple-demand (MD) network”, is recruited by diverse cognitive tasks, both linguistic and non-linguistic. I characterize these two networks across four studies: first, I ask how functionally integrated each network is and how cognitively separable their respective computations are, by measuring the synchronization within each network and across the two networks. Second, I use the two-network framework to propose a new perspective on cortical reorganization of language abilities following brain damage, by examining how these networks alter their functional profiles in people with post-stroke aphasia. Third, I characterize the respective contributions of these networks to comprehension by contrasting their respective abilities to track linguistic input. Finally, I explore the internal architecture of the language network by estimating the timescales over which different language regions integrate linguistic information. Collectively, the results I obtain constrain cognitive accounts of comprehension and challenge common theoretical views, providing novel insights into the ontology of linguistic mechanisms that give rise to human language.
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