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Dornhoffer lab
DornhofferJohnL@uams
Subjective tinnitus, the perception of sound in the
absence of acoustic stimulation, is a common phenomenon, affecting
approximately 17% of the general population. About one-fourth of these
individuals seek professional help due to associated mood, sleep, and
attentional disturbances. The exact mechanisms of tinnitus generation
and the related central nervous system dysfunction are unknown, making
diagnosis and treatment difficult and often empirical. While most
believe that the inciting event for tinnitus generation lies in cochlear
or auditory nerve dysfunction, the perception of tinnitus can be
ascribed to central mechanisms in most cases. Although many tinnitus
sufferers complain of poor concentration, neuropsychological testing has
revealed that the cognitive defficiency appears to be associated with
the control of attention, especially the inhibition of attention
task–irrelevant activity.
We used the sleep state-dependent midlatency
auditory evoked P50 potential to assess the level of arousal and of
habituation to repetitive stimuli in tinnitus patients and in age- and
gender-matched control subjects. No significant difference in the
amplitude of the P50 potential was evident between individuals with
tinnitus and age-matched controls. This suggests that tinnitus patients
have no detectable impairment in the level of arousal using the P50
potential. There were, however, significant differences in habituation
in the tinnitus group at the 250-msec and 1000-msec ISI. This is in
agreement with Hallum’s theory that tinnitus represents a fundamental
deficit in habituation. Impaired habituation leading to a sensory
gating deficit may explain some of the attentional deficits and
cognitive disturbances described in tinnitus patients. Our findings,
likewise, are in agreement with a subcortical source of habituation and
suggest a deficit in sensory gating may be present in tinnitus
sufferers.
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