Multitask Language Mapping to Visualize the Spatial Configuration of Polyfunctional Language Cortex.

Abstract

Direct electrical stimulation (DES) remains the gold standard for identifying eloquent language cortex. However, most protocols rely on single-task mapping, typically visual naming, potentially overlooking modality-specific or distributed language areas. The aim of this study was to define the spatial extent of polyfunctional language cortex using multitask DES integrated with the Yale Brain Atlas (YBA) and to supplement this with population-based structural connectivity data. We retrospectively analyzed patients with drug-resistant focal epilepsy who underwent intracranial EEG monitoring and extraoperative DES language mapping at Yale (2017-2022). Six tasks were administered at each bipolar contact pair: visual naming, auditory naming, reading, repetition, auditory comprehension, and written comprehension. Responses were mapped to the YBA (∼1-cm² resolution), normalized for amperage and sampling frequency, and aggregated across patients. Intertask correlations were assessed using Kendall rank coefficients. Structural connectivity between language-involved parcels was evaluated using deterministic tractography from diffusion data of 1,065 healthy participants. Analyses were conducted using Python 3.9.13. Fifteen patients were included (mean age, 42.8 ± 14.1 years; 53% male). Multitask mapping identified a reproducible "language core" involving the superior temporal gyrus, pars triangularis, anterior supramarginal gyrus, and a basal temporal area located 4-6 cm posterior to the temporal tip. A tiered task strategy-visual naming, auditory naming, and reading-captured over 99% of all language-positive sites. At the individual level, up to 16% (8.2%-15.9%) of parcels cleared by visual naming alone exhibited disruption with other tasks, notably reading. Intertask correlation was highest between auditory naming and visual naming (<i>p</i> < 0.0001, τ = 0.70, 95% CI 0.61-0.78). Structural connectivity analysis showed involvement of the arcuate fasciculus (76.9%), parietal aslant tract (85.4%), and superior longitudinal fasciculus (73.9%). The supramarginal region had the densest language connectivity (69.2%), although connectivity strength did not correlate with DES-defined language involvement (τ = -0.14, <i>p</i> = 0.11). Multitask DES anchored to the YBA provides an anatomically precise, reproducible platform for language mapping. A focused task set enhances efficiency without sacrificing sensitivity. Integration with structural connectivity offers network-level insights. Limitations include modest sample size, variable electrode coverage with undersampling of the anterior language areas, and patient population with epilepsy, which may affect generalizability. This multimodal framework informs surgical planning and advances our understanding of human language representation.