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Threshold-duration functions of chinchilla auditory nerve fibers
Hearing Research 124 (1998) 190
Letter to the Editor
Threshold-duration functions of chinchilla auditory nerve ¢bers Ann Clock Eddins a; *, Richard J. Salvi b , Jian Wang b , Nicholas L. Powers a
b
Auditory Physiology Lab, Department of Speech and Hearing Sciences, Indiana University, 200 S. Jordan Avenue, Bloomington, IN 47405, USA b Hearing Research Lab, State University of New York at Bu¡alo, Bu¡alo, NY, USA
Sir, This study estimated single-unit thresholds as a function of signal duration using an adaptive, two-interval forced-choice paradigm (2IFC). The authors want to make the readers aware of bias introduced into the threshold estimation process by our implementation of the 2IFC procedure. In this procedure, spikes were counted during a tone and no-tone interval, and the total spike count was used as the decision variable. A correct response was recorded if the spike count was greater in the tone than the no-tone interval. An incorrect response was recorded if the spike count was greater in the no-tone than the tone interval. An incorrect response was also recorded when the spike count was equal in the two intervals: this produced a biased decision procedure and contributed to slightly higher threshold estimates. The resulting bias was small and likely did not have any in£uence on the overall results of the study. An alternative approach to eliminate bias when the counts are equal is to simulate guessing by increasing the number of correct responses by 0.5, cor-
responding to the asymptotic guessing rate in a 2IFC task (Delgutte, 1987, 1990 ; Relkin and Pelli, 1987). Intuitively, one might be led to simulate guessing using a random number generator. However, doing so will add irrelevant noise to the threshold estimation procedure. The latter is what was referred to as `additional noise due to guessing' in the personal communication attributed to Relkin in the original paper. The authors thank Dr. Evan Relkin for prompting this clari¢cation.
References Delgutte, B., 1987. Peripheral auditory processing of speech information: Implications from a physiological study of intensity discrimination. In: Schouten, M.E.H. (Ed.), The Psychophysics of Speech Perception, pp. 333^353. Nijhof, Dordrecht. Delgutte, B., 1990. Physiological mechanisms of psychophysical masking: Observations from auditory-nerve ¢bers. J. Acoust. Soc. Am. 87, 791^809. Relkin, E.M., Pelli, D.G., 1987. Probe tone thresholds in the auditory nerve measured by two-interval forced-choice procedures. J. Acoust. Soc. Am. 82, 1679^1691.
* Corresponding author. Tel.: +1 (812) 855-5407; Fax: +1 (812) 855-5531; E-mail: [email protected] 0378-5955 / 98 / $19.00 ß 1998 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 8 - 5 9 5 5 ( 9 8 ) 0 0 1 2 8 - 2
HEARES 3092 15-10-98
Letter to the Editor
Threshold-duration functions of chinchilla auditory nerve ¢bers Ann Clock Eddins a; *, Richard J. Salvi b , Jian Wang b , Nicholas L. Powers a
b
Auditory Physiology Lab, Department of Speech and Hearing Sciences, Indiana University, 200 S. Jordan Avenue, Bloomington, IN 47405, USA b Hearing Research Lab, State University of New York at Bu¡alo, Bu¡alo, NY, USA
Sir, This study estimated single-unit thresholds as a function of signal duration using an adaptive, two-interval forced-choice paradigm (2IFC). The authors want to make the readers aware of bias introduced into the threshold estimation process by our implementation of the 2IFC procedure. In this procedure, spikes were counted during a tone and no-tone interval, and the total spike count was used as the decision variable. A correct response was recorded if the spike count was greater in the tone than the no-tone interval. An incorrect response was recorded if the spike count was greater in the no-tone than the tone interval. An incorrect response was also recorded when the spike count was equal in the two intervals: this produced a biased decision procedure and contributed to slightly higher threshold estimates. The resulting bias was small and likely did not have any in£uence on the overall results of the study. An alternative approach to eliminate bias when the counts are equal is to simulate guessing by increasing the number of correct responses by 0.5, cor-
responding to the asymptotic guessing rate in a 2IFC task (Delgutte, 1987, 1990 ; Relkin and Pelli, 1987). Intuitively, one might be led to simulate guessing using a random number generator. However, doing so will add irrelevant noise to the threshold estimation procedure. The latter is what was referred to as `additional noise due to guessing' in the personal communication attributed to Relkin in the original paper. The authors thank Dr. Evan Relkin for prompting this clari¢cation.
References Delgutte, B., 1987. Peripheral auditory processing of speech information: Implications from a physiological study of intensity discrimination. In: Schouten, M.E.H. (Ed.), The Psychophysics of Speech Perception, pp. 333^353. Nijhof, Dordrecht. Delgutte, B., 1990. Physiological mechanisms of psychophysical masking: Observations from auditory-nerve ¢bers. J. Acoust. Soc. Am. 87, 791^809. Relkin, E.M., Pelli, D.G., 1987. Probe tone thresholds in the auditory nerve measured by two-interval forced-choice procedures. J. Acoust. Soc. Am. 82, 1679^1691.
* Corresponding author. Tel.: +1 (812) 855-5407; Fax: +1 (812) 855-5531; E-mail: [email protected] 0378-5955 / 98 / $19.00 ß 1998 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 8 - 5 9 5 5 ( 9 8 ) 0 0 1 2 8 - 2
HEARES 3092 15-10-98