David López-Ramos , Luis E. López-Bascuas , Almudena Eustaquio-Martín , Enrique A. Lopez-Poveda
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引用次数: 0
Abstract
Cochlear tuning and hence auditory frequency selectivity are thought to change in noisy environments by activation of the medial olivocochlear reflex (MOCR). In humans, auditory frequency selectivity is often assessed using psychoacoustical tuning curves (PTCs), a plot of the level required for pure-tone maskers to just mask a fixed-level pure-tone probe as a function of masker frequency. Sometimes, however, the stimuli used to measure a PTC are long enough that they can activate the MOCR by themselves and thus affect the PTC. Here, PTCs for probe frequencies of 500 Hz and 4 kHz were measured in forward masking using short maskers (30 ms) and probes (10 ms) to minimize the activation of the MOCR by the maskers or the probes. PTCs were also measured in the presence of long (300 ms) ipsilateral, contralateral, and bilateral broadband noise precursors to investigate the effect of the ipsilateral, contralateral, and bilateral MOCR on PTC tuning. Four listeners with normal hearing participated in the experiments. At 500 Hz, ipsilateral and bilateral precursors sharpened the PTCs by decreasing the thresholds for maskers with frequencies at or near the probe frequency with minimal effects on thresholds for maskers remote in frequency from the probe. At 4 kHz, by contrast, ipsilateral and bilateral precursors barely affected thresholds for maskers near the probe frequency but broadened PTCs by reducing thresholds for maskers far from the probe. Contralateral precursors barely affected PTCs. An existing computational model was used to interpret the results. The model suggested that despite the apparent differences, the pattern of results is consistent with the ipsilateral and bilateral MOCR inhibiting the cochlear gain similarly at the two probe frequencies and more strongly than the contralateral MOCR.
期刊介绍:
The aim of the journal is to provide a forum for papers concerned with basic peripheral and central auditory mechanisms. Emphasis is on experimental and clinical studies, but theoretical and methodological papers will also be considered. The journal publishes original research papers, review and mini- review articles, rapid communications, method/protocol and perspective articles.
Papers submitted should deal with auditory anatomy, physiology, psychophysics, imaging, modeling and behavioural studies in animals and humans, as well as hearing aids and cochlear implants. Papers dealing with the vestibular system are also considered for publication. Papers on comparative aspects of hearing and on effects of drugs and environmental contaminants on hearing function will also be considered. Clinical papers will be accepted when they contribute to the understanding of normal and pathological hearing functions.