Evoked cochlear potentials in the barn owl.
Gross electrical responses to tone bursts were measured in adult barn owls, using a single-ended wire electrode placed onto the round window. Cochlear microphonic (CM) and compound action potential (CAP) responses were evaluated separately. Both potentials were physiologically vulnerable. Selective abolishment of neural responses at high frequencies confirmed that the CAP was of neural origin, while the CM remained unaffected. CAP latencies decreased with increasing stimulus frequency and CAP amplitudes were correlated with known variations in afferent fibre numbers from the different papillar regions. This suggests a local origin of the CAP along the tonotopic gradient within the basilar papilla. The audiograms derived from CAP and CM threshold responses both showed a broad frequency region of optimal sensitivity, very similar to behavioural and single-unit data, but shifted upward in absolute sensitivity. CAP thresholds rose above 8 kHz, while CM responses showed unchanged sensitivity up to 10 kHz.
Köppl
Christine
C
Lehrstuhl für Zoologie, Technische Universität München, Lichtenbergstr. 4, 85747 Garching, Germany. ckoeppl@physiol.usyd.edu.au
Gleich
Otto
O
D000161:Acoustic Stimulation; D000758:Anesthesia; D000818:Animals; D001309:Auditory Threshold / Q000187:drug effects / Q000502:physiology; D003055:Cochlear Microphonic Potentials / Q000187:drug effects / Q000502:physiology*; D003627:Data Interpretation, Statistical; D004567:Electrodes, Implanted; D004594:Electrophysiology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D006198:Hair Cells, Auditory / Q000187:drug effects / Q000502:physiology; D020305:Strigiformes / Q000502:physiology*; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology
D018690:Excitatory Amino Acid Agonists; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid