MD/PhD Student The University of Texas Health Science Center at Houston Houston, Texas, United States
Introduction: Naming deficits are a common complication of surgical resections in the language-dominant hemisphere. While various brain regions are hypothesized to support separable processes, the language network and its functional mapping to naming remain unclear. However, such knowledge could improve the localization of critical brain regions to preserve language function. We used ECoG to identify brain networks involved in naming using multimodal stimuli with convergent design.
Methods: Data were obtained from epilepsy patients who underwent invasive electrophysiology. Recordings were acquired during cued-naming tasks using pictures (patients=154, electrodes=16,229), auditory descriptions (patients=119, electrodes=12,347), and orthographic descriptions (patients=73, electrodes=8,716). We identified the lexical-semantic network using a mixed-effects multilevel analysis to estimate group-level gamma power (65-115Hz). We then characterized the associated network dynamics using a multivariate autoregressive model and quantified interactions between regions with partial directed coherence.
Results: Auditory and orthographic naming engaged an identical lexical access network consisting of the posterior middle temporal gyrus (pMTG), the middle fusiform gyrus (mFus), the intraparietal sulcus (IPS), and the inferior frontal gyrus (IFG). Visual naming also engaged the same lexical access network except for the absence of pMTG. Furthermore, peak outflow from mFus, IPS, and IFG was strongest between these regions and occurred following modality-specific sensory processing in all tasks. Outflow from pMTG was only seen in auditory and orthographic naming and occurred just prior to peak outflow from the previous regions.
Conclusion : These results reveal that mFus, IPS, and IFG constitute a core heteromodal lexical access network and implicate the role of pMTG as a lexical interface during comprehension. Juxtaposing the cortical network dynamics of lexical access across different conceptual representations better informs our understanding of both specialized and shared cortical language networks, which provides important insights that could influence surgical approaches to minimize postoperative language deficits.
