Neural competition between concurrent speech production and other speech perception

Understanding others' speech while individuals simultaneously produce speech utterances implies neural competition and requires specific mechanisms for a neural resolution given that previous studies proposed opposing signal dynamics for both processes in the auditory cortex (AC). We here used neuroimaging in humans to investigate this neural competition by lateralized stimulations with other speech samples and ipsilateral or contralateral lateralized feedback of actively produced self speech utterances in the form of various speech vowels. In experiment 1, we show, first, that others' speech classifications during active self speech lead to activity in the planum temporale (Pte) when both self and other speech samples were presented together to only the left or right ear. The contralateral PTe also seemed to indifferently respond to single self and other speech samples. Second, specific activity in the left anterior superior temporal cortex (STC) was found during dichotic stimulations (i.e. self and other speech presented to separate ears). Unlike previous studies, this left anterior STC activity supported self speech rather than other speech processing. Furthermore, right mid and anterior STC was more involved in other speech processing. These results signify specific mechanisms for self and other speech processing in the left and right STC beyond a more general speech processing in PTe. Third, other speech recognition in the context of listening to recorded self speech in experiment 2 led to largely symmetric activity in STC and additionally in inferior frontal subregions. The latter was previously reported to be generally relevant for other speech perception and classification, but we found frontal activity only when other speech classification was challenged by recorded but not by active self speech samples. Altogether, unlike formerly established brain networks for uncompetitive other speech perception, active self speech during other speech perception seemingly leads to a neural reordering, functional reassignment, and unusual lateralization of AC and frontal brain activations.