Spatiotemporal Dynamics of Language Information Representation within the Left Inferior Parietal Lobule Network: An Intracranial SEEG Study.

The left inferior parietal lobe (IPL) supports diverse cognitive functions through the finely differentiated yet coordinated interactions of its subregions, including the supramarginal gyrus (SMG), angular gyrus (AG) and lateral bank of the intraparietal sulcus (lbIPS). However, how these subregions dynamically represent and exchange information during cognitive processing remains unclear. Language processing, integrating visual form, phonology, and semantics, provides an ideal model for investigating the IPL's functional capabilities and dynamics. To overcome the limitations of traditional neuroimaging techniques that lack the spatiotemporal resolution to capture these fast-evolving processes, and univariate analyses unable to detect fine-grained representational structure in neural signals, we employed stereo-electroencephalography (SEEG) in 13 epilepsy patients (8 males and 5 females) performing an oral word reading task. Combining SEEG with representational similarity analysis (RSA), a multivariate approach linking neural activity patterns to cognitive models, we mapped spatiotemporal language information dynamics across IPL subregions. Results revealed dynamic functional differentiation within the left IPL: the SMG and AG exhibited sequential language representations, with the SMG showing early semantics, followed by phonology and later visual form and semantics; the AG showed early semantics followed by visual form; in contrast, the lbIPS was engaged only in visual form representation. Connectivity analyses revealed the dynamic coordination among IPL subregions throughout the task. These findings demonstrate that the left IPL operates as a dynamic network, where functional specialization and interregional information exchange collectively support complex cognitive processes.Significance statement This study sheds light on the intricate spatiotemporal dynamics of different types of information during oral word reading within the left inferior parietal lobule (IPL), a critical region for integrating multidimensional information. Using high spatiotemporal resolution intracranial stereo-electroencephalography (SEEG) recordings from epilepsy patients and a multivariate representational similarity analysis (RSA) approach to examine fine-grained information dynamics, we identified how IPL subregions process distinct language information in a temporal sequence and how information flows across these regions. These findings provide a dynamic view of IPL function, moving beyond traditional static models.