Influence of focused auditory attention on cochlear activity in humans

The mammalian auditory system contains descending pathways that originate i n the cortex and relay at various intermediate levers before reaching the p eripheral sensory organ of Corti. The last link in this chain consists of t he olivocochlear bundle. The activity of this bundle can be measured throug h otoacoustic emissions, which are acoustic signatures of the cochlear biom echanical activity. In the present study, it was hypothesized that frequenc y-specific activation of the olivocochlear bundle in the contralateral ear would show up as frequency-specific Variations in otoacoustic emission ampl itude in the ipsilateral ear. Two groups of young adult subjects participat ed in this experiment. Evoked otoacoustic emissions were recorded in the ip silateral ear at two test frequencies (1 and 2 kHz). Subjects had to detect probe tones at a given frequency in background noise in the contralateral ear. Larger efferent activation was measured at test frequencies on which a ttention is focused. This result provides evidence for an influence of atte ntion on the auditory periphery via descending projections.