Task-related differences in temporo-parietal cortical activation during human phonatory behaviors

Functional magnetic resonance imaging (fMRI) was used to investigate cortical activity related to differential control of the human phonatory system during a sentence production task. Our focus in this report was on activation of the temporo-parietal (TP) junctional region, suggested by recent models in speech production/perception to play a critical role between self-generated acoustic and associated somatosensory inputs related to the consequences of speech. Thirteen healthy participants produced multiple trials of phonetically balanced sentences during each of three performance conditions: "covert", "whisper" and "voice". An event-related, sparse sampling fMRI method was used to examine TP activity associated with sentence production during each condition. Results demonstrated differential responsiveness in the TP region bilaterally as a function of task conditions, with covert production generating the highest level of TP activation. These results suggest that the TP region is differentially responsive to phonation-specific production variables. Our finding that covert production instead of overt voicing resulted in the greatest activity in TP is consistent with recent reports demonstrating TP activation related to temporal ordering judgments and task-dependent memory use.