A Comparison of Efferent Suppression of Compound Action Potentials by Simultaneous and Non-simultaneous Contralateral Noise Paradigms

Abstract

The intent of this study was to compare the effectiveness of continuous versus gated contralateral noise in producing efferent suppression of CAPs in guinea pigs. The average contralateral suppression was 2.0 dB when using gated noise, with ipsilateral tone-pip rates of 2 s⁻¹, and 1.4 dB when using continuous noise at an ipsilateral tone-pip rate of 31 s⁻¹. When the ipsilateral tone-pip rate employed in the simultaneous paradigm with continuous noise was reduced to 2 s⁻¹ a rate equivalent to that employed in the non-simultaneous paradigm, the average attenuation was 2.1 dB, a magnitude comparable to the suppression achieved using gated noise. The present data suggest that, when equated for ipsilateral tone-pip pulse rate, simultaneous and non-simultaneous contralateral masking paradigms produce comparable levels of efferent suppression.

Key Words:

• Medial olivocochlear efferents
• Compound action potential
• Contralateral efferent suppression
• Contralateral noise