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.

Psychophysical Tuning Curves in Subjects with Tinnitus Suggest Outer Hair Cell Lesions

1995 ◽  
Vol 113 (3) ◽  
pp. 223-233 ◽  
Author(s):  
Curtin R. Mitchell ◽  
Thomas A. Creedon
Keyword(s):  
Hearing Loss ◽  
Hair Cell ◽  
Hair Cells ◽  
Outer Hair Cell ◽  
Tuning Curve ◽  
Control Design ◽  
Nerve Fibers ◽  
Outer Hair Cells ◽  
Tuning Curves ◽  
Hearing Thresholds

A study by Penner (J Speech Hear Res 1980;23:779–86) found evidence for Impaired lateral suppression in subjects with tinnitus and sensorineural hearing loss. If lateral suppression is related to tuning curve sharpness and lateral suppression is impaired, the shape of the tuning curve should be affected. The purpose of this study was to determine whether subjects with tinnitus have psychophysical tuning curves that are different from those of subjects without tinnitus. Psychophysical tuning curves and hearing thresholds were obtained from 18 subjects, 7 with tinnitus and 11 without tinnitus. Only subjects with normal audiograms (through 8 kHz) were selected for this study. In subjects with tinnitus psychophysical tuning curves were obtained in the region pitch-matched to their tinnitus. In nontinnitus subjects psychophysical tuning curves were determined at the same frequencies as for the tinnitus subjects in a yoked-control design. The slopes of the tails and tips and the Q10 and other measures were calculated for each tuning curve. The psychophysical tuning curves in subjects with tinnitus were significantly different (0.01 level) from those of control subjects and often had hypersensitive tails and some elevated tips. These shapes of tuning curves are consistent with cochlear lesions involving the loss of outer hair cells without damage to the Inner hair cells or nerve fibers.

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