Using TMS to evaluate a causal role for right posterior temporal cortex in talker-specific phonetic processing

Theories suggest that speech perception is informed by listeners' beliefs of what phonetic variation is typical of a talker. A previous fMRI study found right middle temporal gyrus (RMTG) sensitivity to whether a phonetic variant was typical of a talker, consistent with literature suggesting that the right hemisphere may play a key role in conditioning phonetic identity on talker information. The current work used transcranial magnetic stimulation (TMS) to test whether the RMTG plays a causal role in processing talker-specific phonetic variation. Listeners were exposed to talkers who differed in how they produced voiceless stop consonants while TMS was applied to RMTG, left MTG, or scalp vertex. Listeners subsequently showed near-ceiling performance in indicating which of two variants was typical of a trained talker, regardless of previous stimulation site. Thus, even though the RMTG is recruited for talker-specific phonetic processing, modulation of its function may have only modest consequences.

Automated summary

The study suggests that listeners' beliefs about phonetic variation in speech perception play a role in informing their perception. Previous fMRI research found that the right middle temporal gyrus (RMTG) is sensitive to typical phonetic variants used by a talker. This current study used transcranial magnetic stimulation (TMS) to test if RMTG has a causal role in processing talker-specific phonetic variation. The results showed that regardless of stimulation site (RMTG, left MTG, or scalp vertex), listeners could accurately identify which variant was typical of a trained talker.