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Abstract:
Introduction
: The ability to inhibit irrelevant sensory input is an essential
protective function . It is as important to be able to respond
appropriately to incoming novel stimuli. The P50 auditory evoked
potential (EP) is believed to reflect a pre-attentive stage of
information processing and has been used to examine the "sensory
gating ability" of the CNS.
Methods
: Fifteen healthy adults were subjected to paired-click paradigms
where in one the two clicks ( S1 & S2) were identical (ID) and
in the other two they were unidentical (UI) . In one UI paradigm
the frequency of the S2 was higher, and in the other lower, than
the frequency of S1 stimuli. Subjects were not required to perform
any tasks.
Results
: The S2/S1 amplitude ratios differed significantly between the UI
paradigms and the ID paradigm. The ratio was higher in the UI
paradigm with a higher frequency S2 (df=16, p<.007), and with a
lower frequency S2 (df=16, p<.003). The two UI paradigms did not
differ from one another.
Conclusions
: The CNS of normal individuals responds to stimulus change by
decreasing the degree of attenuation of the resulting EP. This
effect is robust and is evident as early as 50 msec
post-stimulation.
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