Rapid auditory and phonemic processing relies on the left planum temporale

After initial bilateral acoustic processing of the speech signal, much of the subsequent language processing is left-lateralized, perhaps due to a left hemisphere (LH) advantage for rapidly unfolding components of speech. Here we investigated whether and where damage to the LH predicted impaired performance on judging the directionality of frequency modulated (FM) sweep stimuli that changed within short (25 msec) or longer (250 msec) temporal windows. Performance was significantly lower for stroke survivors (n = 50; 18 female) than controls (n = 61; 34 female) on FM Sweeps judgments, particularly on the short sweeps. Support vector regression lesion-symptom mapping revealed that part of the left planum temporale (PT) was related to worse performance on the short FM sweeps, controlling for performance on the long sweeps. We then investigated whether damage to this region related to diminished performance on stop consonant identification and pseudoword repetition, which theoretically depend on rapid auditory processing. Indeed, participants with PT lesions (PT lesion+, n = 24) performed worse than those without (PT lesion-, n = 26) on stop consonant identification and pseudoword repetition, controlling for lesion size and hearing ability. PT lesions impacted pseudoword repetition more than real word repetition, which is of interest because pseudowords rely solely on speech sound perception and sequencing, whereas words can also rely on lexical-semantic knowledge. We conclude that the left PT is a critical region for processing auditory information in short temporal windows, and it may also be an essential transfer point in auditory-to-linguistic processing.