Brain Networks of Noun Generation

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 DESCRIPTION (provided by applicant): Speech production relies upon a distributed network that is disrupted by a variety of neurological diseases including trauma, stroke, neuro-degeneration and neoplasms. Despite the central role of language in human behavior, our understanding of linguistic disorders and the development of appropriate treatment strategies is impeded by the absence of biologically instantiated models to explain one of the most basic of language processes - the production of words. We propose to use intracranial electroencephalographic (icEEG) recordings to generate a network-based description of the within region (Broca's area, insula and temporal pole) as well as inter-regional dynamics and use this data to critically evaluate current neuro-linguistic models and a model proposed by our group. We will cross-validate these findings using a novel direct cortical stimulation approach. We will collect high spatio-temporal resolution datasets during naming of objects, people and places from a large cohort of neurosurgical patients (n=70) and generate a network representation of information flow between visual, frontal, insular and temporal pole regions during word production. We hypothesize that word production relies on local cortical networks, coupled with long-range interactions within more distributed language network. This hypothesis will be tested with multiple analytic pipelines (using amplitude envelope correlations, phase locking values, phase-amplitude coupling and directed transfer functions). We will implement chronometrically controlled closed loop cortical stimulation - timed to the onset of focal high gamma band activity - to induce transient dysfunction of critical word production nodes enabling assessment of the causality of the icEEG data. We will leverage our expertise with measuring induced current spreads in the brain, by studying the effect of ongoing network processes on the amplitude and latency of cortico-cortical evoked potentials and high gamma activity to further assess network representations. In summary, the proposed work aims to investigate the neuro-dynamics of naming at multiple spatial levels (regional and global) using a variety of network analysis methods. The proposed work will provide unique information on the neurobiology of word production with broad implications for the understanding of normal language and for the clinical management of patients with anomia.