Compound action potential thresholds and tuning curves in the alligator lizard

1986 ◽  
Vol 79 (6) ◽  
pp. 1873-1882 ◽  
Author(s):  
Robert G. Turner ◽  
Neil T. Shepard
Keyword(s):  
Action Potential ◽  
Compound Action Potential ◽  
Tuning Curves ◽  
Alligator Lizard ◽  
Compound Action

Compound Action-Potential Tuning Curves in Normal and Acoustically Traumatized Cats

1983 ◽  
Vol 92 (5) ◽  
pp. 496-503 ◽  
Author(s):  
Neil T. Shepard ◽  
Paul J. Abbas
Keyword(s):  
Action Potential ◽  
Hair Cells ◽  
Tuning Curve ◽  
Compound Action Potential ◽  
Outer Hair Cells ◽  
Signal Frequency ◽  
Control Group ◽  
Tail Region ◽  
Tuning Curves ◽  
Compound Action

Compound action-potential tuning curves, using a forward-masking paradigm, were developed on both a control group and a group of acoustically traumatized cats. Differences observed between the two populations included a decrease in the sharpness of the tip, in the sensitivity of the tip, and/or in the sensitivity of the tail region. Phase-contrast light microscopy was performed on all exposed ears using a celloidin-embedding technique with horizontal sectioning. Whenever an abnormality in an action-potential tuning curve was seen, histological evidence of damage to the organ of Corti in an appropriate region corresponding to the signal frequency was observed. However, several cases of damage to the cochlea were observed with normal tuning curves. Whenever the tip region of the tuning curve was elevated, evidence of damage to all three rows of outer hair cells and to the inner hair cells was seen.

The Effect of Contralateral Pure Tones on the Compound Action Potential in Humans: Efferent Tuning Curves

2016 ◽  
Vol 27 (02) ◽  
pp. 103-116 ◽  
Author(s):  
Fadi Najem ◽  
John Ferraro ◽  
Mark Chertoff
Keyword(s):  
Action Potential ◽  
Otoacoustic Emissions ◽  
Pure Tone ◽  
Compound Action Potential ◽  
Clinical Tool ◽  
Experimental Conditions ◽  
Tuning Curves ◽  
Contralateral Stimulation ◽  
Pure Tones ◽  
Compound Action

Background: The compound action potential (CAP) has been suggested in the literature as an alternative to otoacoustic emissions for evaluating the efferent auditory system. However, very few studies have examined efferent influence on auditory nerve potentials in humans. Purpose: This study examines the effects of presenting contralateral pure tones on the ipsilateral CAP onset and offset amplitudes as a potential clinical tool for the assessment of efferent auditory function. Research Design: CAPs for 1- and 4-kHz tone pips (TPs) and clicks were recorded from 9, 9, and 8 participants, respectively. Contralateral tones were presented at levels ranging from 20 to 70 dB HL in 10-dB steps. The frequencies of the contralateral tones were 0.5, 1, 2 kHz for the 1-kHz TP CAP; 2, 4, 8 kHz for the 4-kHz TP CAP; and 0.5, 1, 2, 4, 8 kHz for the click CAP. Data Analysis: The CAP onset and offset amplitudes in all experimental conditions were analyzed and compared to the CAP amplitude without contralateral stimulation (i.e., baseline). Results: Maximum suppression of 1-kHz TP CAP onset amplitude was obtained in seven out of nine participants by the 1-kHz contralateral pure tone at 40 dB HL. The 4-kHz TP CAP onset amplitude was maximally suppressed in eight out of nine participants by the 8-kHz contralateral pure tone at 30 dB HL. The click CAP offset amplitude was maximally suppressed in four out of eight participants by the 8-kHz contralateral tone presented at 40 dB HL. The 1- and 4-kHz TP CAP offset and click CAP onset amplitudes were not affected by contralateral stimulation. Conclusions: These results along with the previous studies may suggest that the efferent system is maximally stimulated by moderate signal-level tones (i.e., 30–40 dB HL), and that efferent activity is dependent on frequency cues of both the stimulus and suppressor tones. Other factors that might be affecting efferent influence on the CAP in humans such as sound duration, phase, bandwidth, and periodicity need to be further investigated.

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