Effects of orienting attention to a specific frequency on medial olivocochlear reflex - A study of dependence on target frequencies -

The medial olivocochlear bundle responds to acoustic stimuli and suppresses outer hair cell gain. This reflex response is called the medial olivocochlear reflex (MOCR) and improves signal detection in background noise, referred to anti-masking effect. Our previous study reported that orienting attention to moderate frequencies selectively increases MOCR near the attended frequency, and that the effects of attention to low and high frequencies are unlikely to appear in MOCR. The previous investigation was limited to the condition where participants kept orienting attention to the same frequency across trials. Here we examined the condition where participants switched attention to different frequencies trial by trial. During the measurements of MOCR, participants detected probe tones in background noise. The target frequency, 750, 1000, 1250, 1500, 2000 and 3000 Hz, was notified by a preceding cue frequency and varied across trials. When the target frequency was 1250 Hz, the MOCR strength tended to be attenuated at lower frequencies. In contrast, for any other target frequencies, MOCR didn't differ significantly from a non-attentional condition. The frequency range where attentional effect was observed was similar to our previous report. The similarity implicates that MOCR can covary with dynamically changing frequency-specific attention, which would help exerting antimasking effect flexibly.