Towards an objective test of chronic tinnitus: Properties of auditory cortical potentials evoked by silent gaps in tinnitus-like sounds
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Hearing Research April 2018Abstract: A common method designed to identify if an animal hears tinnitus assumes that tinnitus “fills-in” silent
gaps in background sound. This phenomenon has not been reliably demonstrated in humans. One test of
the gap-filling hypothesis would be to determine if gap-evoked cortical potentials are absent or attenuated
when measured within background sound matched to the tinnitus sensation. However the tinnitus
sensation is usually of low intensity and of high frequency, and it is unknown if cortical responses can be
measured with such “weak” stimulus properties. Therefore the aim of the present study was to test the
plausibility of observing these responses in the EEG in humans without tinnitus. Twelve non-tinnitus
participants heard narrowband noises centered at sound frequencies of 5 or 10 kHz at sensation levels
of either 5, 15, or 30 dB. Silent gaps of 20 ms duration were randomly inserted into noise stimuli, and
cortical potentials evoked by these gaps were measured by 64-channel EEG. Gap-evoked cortical responses
were statistically identifiable in all conditions for all but one participant. Responses were not
significantly different between noise frequencies or levels. Results suggest that cortical responses can be
measured when evoked by gaps in sounds that mirror acoustic properties of tinnitus. This design can
validate the animal model and be used as a tinnitus diagnosis test in humans.
A common method designed to identify if an animal hears tinnitus assumes that tinnitus “fills-in” silent
gaps in background sound. This phenomenon has not been reliably demonstrated in humans. One test of
the gap-filling hypothesis would be to determine if gap-evoked cortical potentials are absent or attenuated
when measured within background sound matched to the tinnitus sensation. However the tinnitus
sensation is usually of low intensity and of high frequency, and it is unknown if cortical responses can be
measured with such “weak” stimulus properties. Therefore the aim of the present study was to test the
plausibility of observing these responses in the EEG in humans without tinnitus. Twelve non-tinnitus
participants heard narrowband noises centered at sound frequencies of 5 or 10 kHz at sensation levels
of either 5, 15, or 30 dB. Silent gaps of 20 ms duration were randomly inserted into noise stimuli, and
cortical potentials evoked by these gaps were measured by 64-channel EEG. Gap-evoked cortical responses
were statistically identifiable in all conditions for all but one participant. Responses were not
significantly different between noise frequencies or levels. Results suggest that cortical responses can be
measured when evoked by gaps in sounds that mirror acoustic properties of tinnitus. This design can
validate the animal model and be used as a tinnitus diagnosis test in humans.