Fig. 1: Shared acoustic–phonetic processing in STG across native and foreign speech.

a, Spanish-, English- and Mandarin-speaking ECoG participants passively listened to native and foreign speech. Left, sound envelope and spectrogram of example stimuli. Right, coloured lines indicate speech condition, labelled with the number of participants in each group. b, In an example Spanish listener, the same neural populations are active in response to native (left) and foreign (right) speech. Electrode size indicates magnitude of the peak HFA averaged sentence response; colour indicates speech condition. c, Average HFA sentence response for an example electrode is highly correlated across native and foreign speech (Pearson r(250) = 0.986, P < 0.001). Neural responses time-aligned to sentence onset and offset; colour indicates speech condition. Shaded patches indicate standard error of the mean across sentences. d, Proportions of speech-responsive electrodes for Spanish, English and Mandarin speakers are similar across native (top) and foreign (bottom) speech, ranging from 17% to 27% across groups. e, Speech-responsive electrodes across 20 participants primarily localized to the STG in native (top) and foreign (bottom) speech conditions across hemispheres. Electrode size indicates magnitude of the peak HFA averaged sentence response. Inset histograms show electrode counts across native and foreign speech in each anatomical region. f, Acoustic–phonetic TRF weights across three example electrodes show strong correlations between native (top) and foreign (bottom) speech conditions. Different electrodes show tuning to distinct acoustic–phonetic features common to both languages. g, TRF weights across speech-responsive electrodes for native (top) and foreign (bottom) speech are highly correlated (Pearson r(1,992) = 0.86, P < 0.001). Top, columns (electrodes) ordered by the acoustic–phonetic feature showing the maximal weight. Bottom, columns ordered identical to the top for visual comparison. h, Distribution of TRF native–foreign weight correlations across electrodes (purple) is higher compared to the non-parametric permuted distribution (grey). Black vertical line indicates the 95th percentile in the permuted distribution. Corr, correlation; LH, left hemisphere; middletemp, middle temporal gyrus; parsoperc, pars opercularis; parstriang, pars triangularis; postcent, postcentral gyrus; precent, precentral gyrus; RH, right hemisphere; superiortemp, superior temporal gyrus; supramarg, supramarginal gyrus; surp, surprisal.