Lower boundaries of two-tone suppression regions in the guinea pig.
Lower boundaries of two-tone suppression regions were determined in single fibres of the guinea pig with a tracking algorithm as described by Schmiedt (1982). For a suppressee at CF having a level of 20 dB above the threshold of the tip, suppression at the high-frequency (hf) side of the FTC could almost always be found. With the method used, the percentage of fibres in which suppression could be found at the low-frequency (lf) side of the FTC decreased with decreasing CF. Moreover, the occurrence of lf-suppression decreased for lower suppressee levels for fibres with CF approximately 2-5 kHz. For each fibre the minimum level difference between lf-suppression boundary and tip threshold was larger than 20 dB, for the whole group of fibres the difference was 34 dB on average. The hf-suppression regions sometimes reached below the tip for fibres with CFs in the 4 kHz region. The frequency at the lowest level of the hf-suppression boundary, best suppression frequency or BSF, is related to the CF as: BSF = 0.55 + 1.13 CF. When the suppressee level increased, the lower boundary at the hf side shifted upwards with a rate greater than 1 dB/dB. On the whole the two-tone suppression data in the guinea pig agree with those found in other rodents.
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Ear, Nose and Throat Department, Leiden University Hospital, The Netherlands.
D000161:Acoustic Stimulation; D000200:Action Potentials; D000818:Animals; D001309:Auditory Threshold / Q000502:physiology; D003051:Cochlea / Q000502:physiology*; D004594:Electrophysiology; D006168:Guinea Pigs / Q000502:physiology*; D013045:Species Specificity; D000159:Vestibulocochlear Nerve / Q000502:physiology