Abstract
The gap-prepulse inhibition of the acoustic startle reflex has been widely used as a behavioral method for tinnitus screening in animal studies. The cortical-evoked potential gap-induced inhibition has also been investigated in animals as well as in human subjects. The present study aimed to investigate the effect of age on the cortical N1-P2 complex in the gap-prepulse inhibition paradigm. Fifty-seven subjects, aged 20 to 68 years, without continuous tinnitus, were tested with two effective gap conditions (embedded gap of 50- or 20-ms duration). Retest sessions were performed within one month. A significant gap-induced inhibition of the N1-P2 complex was found in both gap durations. Age differently affected the inhibition, depending on gap duration. With a 50-ms gap, the inhibition decreased significantly with the increase in age. This age-inhibition relationship was not found when using a 20-ms gap. The results were reproducible in the retest session. Our findings suggest that the interaction between age and gap duration should be considered when applying the gap-induced inhibition of the cortical-evoked potential as an objective measure of tinnitus in human subjects. Further studies with tinnitus patients are warranted to identify gap duration that would minimize the effects of age and maximize the difference in the inhibition between those with and without tinnitus.
Highlights
Tinnitus, which affects 10–20% of the world’s population, involves the perception of phantom sounds in the absence of a physical stimulus [1, 2]
The startle response and the N1-P2 complex of cortical-evoked potential showed different sensitivities of the prepulse inhibition (PPI) to drugs such as bromocriptine, and ketanserin or to acute tryptophan depletion [24,25,26]. These findings suggest that the PPI mechanism of cortical-evoked potentials is considered different from that of the startle response, but several studies have suggested that there might be some shared mechanisms between them [27, 28]
We focused on a specific gap-prepulse inhibition (GPI) paradigm, our findings related to the 50-ms gap condition are consistent with previous reports on the effect of age on general temporal processing
Summary
Tinnitus, which affects 10–20% of the world’s population, involves the perception of phantom sounds in the absence of a physical stimulus [1, 2]. Tinnitus might cause severe social and economic difficulties due to interference of the incessant sound with daily activities, causing degradation of the patients’ quality of life [3]. Despite its prevalence and debilitating effects, at present, there is no objective way to diagnose tinnitus. The current use of a patient’s subjective response makes the diagnosis unreliable and hinders the development of effective treatment [4].
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