## 2 Neurocognitive Foundation of Language Decoding
### Neural Basis  
The neural basis of language processing is fundamental for BCI-based language decoding. Key brain regions involved in language processing, their network connectivity patterns, and the spatiotemporal dynamics of neural activities during linguistic tasks provide essential insights for developing effective decoding strategies in regard to BCI applications. Understanding these neural mechanisms is crucial for BCI systems, as they inform the selection of optimal recording sites, guide the design of decoding algorithms, and enable more accurate interpretation of neural signals during language tasks. Figure 2: **(a)** The DRC model of reading processing (adapted from [28]), showing lexical (vocabulary-based) and non-lexical (letter-to-sound conversion) pathways from print to speech output. **(b)** The multicomponent Working Memory Model (adapted from [35]), illustrating interactions between the central executive system and its specialized subsystems (visuo-spatial, episodic, and phonological components), with long-term memory processes. The neural architecture of language processing comprises a sophisticated network of interconnected regions. For BCI-based language decoding, identifying and targeting these specific brain regions is essential for electrode placement and signal acquisition. Two primary areas, Broca's and Wernicke's areas, form the cornerstone of language function. [PERSON]'s area, situated in the left inferior frontal gyrus (Brodmann areas 44 and 45), orchestrates language production, grammatical processing, and articulatory planning [43]. Damage to this region results in expressive aphasia, characterized by impaired speech production, while preserving comprehension capabilities [44]. [PERSON]'s area, located in the posterior section of the superior temporal gyrus (Brodmann area 22), facilitates language comprehension and semantic processing, with lesions leading to receptive aphasia, marked by fluent but semantically impaired speech [45]. These critical language-processing regions and their functional connectivity patterns are illustrated in Figure 3a. While this classical Wernicke-Lichtheim-Geschwind model has dominated the field for over a century, recent evidence suggests that the distribution of labor between these regions is more complex than originally proposed, namely lesions in [PERSON]'s region impair not only language production but also comprehension, while [PERSON]'s region lesions affect both comprehension and production [46; 47]. Nevertheless, the distinct functional roles of these regions provide valuable targets for BCI electrode arrays and inform the development of specialized decoding algorithms for different aspects of language processing. The prefrontal cortex, particularly the dorsolateral and ventrolateral regions, mediates higher-order linguistic functions, including executive control, working memory, and linguistic planning [48]. The temporal auditory regions, specifically Heschl's gyrus and the surrounding areas, process spectrotemporal features of speech signals and phonological representations [49]. The parietal lobe, especially the angular and supramarginal gyri, integrates multimodal linguistic information and facilitates semantic processing [50]. Recent neuroimaging studies have significantly advanced our understanding of language network organization. Through resting-state functional Magnetic Resonance Imaging (fMRI) analysis, [PERSON] et al. identified distinct topographical patterns of functional connectivity within the left inferior frontal, inferior parietal, and temporal regions [51]. Subsequently, [PERSON] demonstrated that these connectivity patterns align with three core components of language processing in the perisylvian cortex: phonology, syntax, and semantics [52].