Extended Data Fig. 1: Overview of the experiment.

Musical notes denote auditory stimuli. (a) We used two block rules and the four possible permutations of local/global standard/deviant auditory sequences across both block rules. (b) Each auditory sequence consisted of four tones of 200 ms duration each, separated by a 400 ms inter-tone interval. The entire stimulus sequence was 2000 ms in duration. The fourth tone of each sequence varied during the test phase. After averaging across trials within each condition, we analyzed signals starting from 200 ms prior to the onset of the first tone to 1000 ms following the offset of the fourth tone (3200 ms duration). (c) For fetal recordings, the mother-to-be postioned her abdomen within the concavity of the MEG sensor array, with a sound balloon between her body and the SARA device delivering auditory tones. (d) Fetal MEG signals were recorded noninvasively in response to auditory tones. To correct for the influence of fetal head orientation and size on MEG signal amplitude, fetal signals were normalized. (e) After birth, a subset of subjects returned to the laboratory as newborns and were recorded from after being placed in a cradle oriented head-first toward the SARA device’s SQUID magnetometer array. Newborns wore infant-friendly headphones for stimulus delivery. (f) As with fetuses, the SARA device recorded cortical signals noninvasively from newborns. Note that photographs in c and e are adapted from ref. ²³. The woman in c and the parents of the infant in e gave consent for identifiable images to be published.