Shared and distinct temporal representations of Chinese words across imaged, silent, and overt speech
How internal speech relates to overt speech remains a fundamental question in speech production: do different forms of speech preserve a common neural representation of the intended word, or does that representation change as speech becomes articulated? We used time-resolved electroencephalography to characterize representations of 10 Chinese words during imagined, silent, and overt speech. Word…
Recent research has explored how internal speech, such as imagined, silent, and overt speech, relates to overt speech in terms of neural representation of words. Utilizing time-resolved electroencephalography, scientists investigated ten Chinese words across these different modes of speech. The study found that word identity could be accurately identified in all three modes; however, the temporal dynamics of these representations differed.
Imagined-speech representations reached their peak earlier and showed less temporal stability compared to silent and overt speech. Silent and overt speech exhibited stronger and more sustained representations. When comparing representations across modes, there was shared word-discriminative information, particularly strong between silent and overt speech.
Yet, the direct comparison of word-level representational geometry showed robust correspondence only between silent and overt speech. This indicates that although there is transferable information across modes, it does not necessarily mean the broader relational structure among words is preserved.
Representational similarity analyses revealed distinct visual-form, semantic, and phonetic dynamics across speech modes. Late visual-form and phonetic information contributed uniquely to the shared geometry observed in silent and overt speech. Controlling for time-matched surface electromyography preserved the overall neural correspondence between silent and overt speech while eliminating the unique phonetic contribution to their shared geometry.
This suggests that peripheral articulation plays a role but does not account for the entirety of this common structure.
Overall, this study highlights that imagined, silent, and overt speech share word representations at varying levels. It also suggests that representational geometry and temporal stability undergo progressive reorganization as internal speech transitions into articulation.
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