Data acquisition followed procedures similar to those conducted in previous work12,38,106.
Participants
Thirty-four patients (17 female) were implanted subdural ECoG grids (Integra or PMT) with 4-mm centre-to-centre electrode spacing and 1.17-mm-diameter contacts (recording tens to hundreds of thousands of neurons107,108) as part of their neurosurgical treatment at either University of California, San Francisco (UCSF) or Huashan Hospital. All participants gave informed written consent to participate in the study before experimental testing. Most electrode grids were placed over the lateral surface of a single hemisphere and were centred around the temporal lobe extending to adjacent cortical areas. The precise location of electrode placement was determined by clinical assessment.
For all participants, age, gender, language background information and which hemisphere was recorded from is included in Extended Data Tables 1–4, where each table corresponds to the respective participant group: English monolingual, Spanish and Mandarin monolingual, Spanish–English bilingual and others with diverse language backgrounds. Which participants were included in each set of analyses is listed in Extended Data Table 5. ECoG recordings with the four Mandarin speakers were conducted at Huashan Hospital while patients underwent awake language mapping as part of their surgical brain-tumour treatment. ECoG recordings with all other participants were conducted at UCSF while patients underwent clinical monitoring for seizure activity as part of their surgical treatment for intractable epilepsy. Most participants in this dataset had epileptic seizure foci that were located in deep medial structures (for example, the insula) or far anterior temporal lobe outside of the main regions of interest in this study, such as the STG. All participants included in this study reported normal hearing and spoken language abilities.
Participant consent
All protocols in the current study were approved by the UCSF Committee on Human Research and by the Huashan Hospital Institutional Review Board of Fudan University. Participants gave informed written consent to take part in the experiments and for their data to be analysed. Informed consent of non-English-speaking participants at UCSF was acquired using a medically certified interpreter platform (Language-Line Solutions), and communication with research staff was facilitated by either in-person or video-call-based interpreters who were fluent in the participant’s native language.
Language questionnaire
All participants were asked to self-report speech comprehension proficiency, age of acquisition and frequency of use for all languages that they were familiar with. Participants who self-identified as Spanish–English bilingual were asked to complete a comprehensive language questionnaire by means of an online Qualtrics survey103.
Neural data acquisition
ECoG signals were recorded with a multichannel PZ5 amplifier connected to an RZ2 digital signal acquisition system (TuckerDavis Technologies (TDT)) with a sampling rate of 3 kHz. During the stimulus presentation, the audio signal was recorded in the TDT circuit and therefore time-aligned with the ECoG signal. Audio stimulus was also recorded with a microphone, and this signal was also recorded in the TDT circuit to ensure accurate time alignment.
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