Brain activation patterns in auditory association area for glottal-stop perception

Objectives: Subjects with cleft lip and/or palate (CLP) often show compensatory misarticulation. Glottal stop (GS) is one of the characteristic compensatory misarticulations in CLP and is known to be difficult to distinguish it for those who are unfamiliar with it. Moreover, the neural processing for perception of GS is not still elucidated. Therefore, the purpose of this study was to investigate the perception of GS compared to normal articulation (NA) in terms of behavioral and brain activation patterns using a functional magnetic resonance imaging (fMRI) technique. Methods: Twenty healthy native Japanese-speaking subjects without CLP participated in the study. Subjects listened to speech samples (NA and GS) through the MR-compatible headphones. Experiment 1 (behavioral study): Subjects were asked to distinguish NA and GS with button-press response, and the accuracy rate (the percentage of correct response) and the reaction time were statistically compared. Experiment 2 (fMRI study): The fMRI data were simultaneously acquired with behavioral data using a T2*-weighted gradient echo-planar imaging sequence with a 1.5T scanner, and were analyzed with special attention to the auditory association area by using statistical parametric mapping (SPM) 5. Results: The reaction time for the perception of GS was significantly longer than that for NA. However, there was no significant difference in the accuracy rate between NA and GS. During listening to GS, the bilateral auditory association areas were more activated than listening to NA. Conclusion: The present study suggests that perception of GS is difficult in healthy subjects without CLP because of longer reaction time and brain activation. Further studies should be conducted in CLP subjects with GS for comparison of neural processing in subjects with/without compensatory misarticulation.