RESUMO
Objective:Clinical application of middle-latency auditor evoked potential (MLAEPs) has been increasing, highlighting the importance of understanding the nature of P50,a componentof middle-latency auditory evoked potential. We manipulated stimulus frequency bands in auditory stimuli in order to investigate the nature of P50 in human auditory evoked potentials.Methods:Two paradigms have been used to obtain P50: one is a conditioning /testing paradigm in which paired of pure tone (1000Hz) are delivered, and the other was presented paired of clicks, both with an intensity of 60 dB sound pressure level above the auditory threshold. A total of 30 healthy volunteers were recruited for this study among Center of genetic engineering (fifteen man and fifteen women, mean age of 36,5). All without consumption of caffeine, cigarettes and drugs. Results:No statistically significant differences occurred between the P50 amplitudes and latencies for the pure tone and those for the clicks.Conclusions:Ourpresent results indicate that P50 in humans may reflect a feed-forward mechanism of the brain where a preceding stimulus drives sensory gating mechanisms in preparation for a second stimulus, but the contained frequency doesn't influence on the P50. Both types (tones or clicks) can be used in the exploration of patient with this evoked potential