Identification of syllables best recognized in acoustic-stimulated functional magnetic resonance imaging

In acoustic-stimulated functional magnetic resonance imaging (fMRI), tasks are performed by subjects either during imaging in the presence of scanning noise or during non-imaging periods without scanning noise. Suitable syllables for voice tasks performed with MRI-compatible headphones are limited during the imaging period with scanning noise. However, suitable syllables for voice tasks during the non-imaging period, without scanning noise, are not yet known. This study aimed to identify suitable syllables for voice tasks during both imaging and non-imaging periods. The subjects were 12 healthy volunteers who were native Japanese speakers. On an answer sheet attached to a wooden board, they were asked to write down the syllables they perceived through MRI-compatible headphones during imaging and non-imaging periods. The rate of accuracy for the perception of syllables was calculated; optimally perceived syllables were defined by a rate of accuracy exceeding the 95% upper confidence limit (UCL). The accuracy of syllable perception was significantly higher (P < 0.01) during the non-imaging period (77.2 ± 5.6%) than during the imaging period (66.3 ± 5.0%). The 95% UCLs obtained from the rates of accuracy were 83.5% during imaging and 88.9% during the non-imaging period. The number of syllables for which the accuracy rate exceeded the 95% UCL was 28 during imaging and 33 during the non-imaging period. These syllables could be used for voice tasks in acoustic-stimulated fMRI during imaging or non-imaging periods.