The cannabinoid receptor 1 (CB1R) is found at several stages in the auditory pathway, but its rol... more The cannabinoid receptor 1 (CB1R) is found at several stages in the auditory pathway, but its role in hearing is unknown. Hearing abilities were measured in CB1R knockout mice and compared to those of wild-type mice. Operant conditioning and the psychophysical Method of Constant Stimuli were used to measure audiograms, gap detection thresholds, and frequency difference limens in trained mice using the same methods and stimuli as in previous experiments. CB1R knockout mice showed deficits at frequencies above 8 kHz in their audiograms relative to wild-type mice. CB1R knockouts showed enhancements for detecting gaps in low-pass noisebursts relative to wild-type mice, but were similar for other noise conditions. Finally, the two groups of mice did not differ in their frequency discrimination abilities as measured by the frequency difference limens task. These experiments suggest that the CB1R is involved in auditory processing and lay the groundwork for future physiological experiments.
Journal of the Acoustical Society of America, 2015
ABSTRACT The current project investigates how experience with human speech can influence speech p... more ABSTRACT The current project investigates how experience with human speech can influence speech perception in budgerigars. Budgerigars are vocal mimics and speech exposure can be tightly controlled in a laboratory setting. The data collected include behavioral responses from 30 budgerigars, tested using a cue-trading paradigm with synthetic speech stimuli. Prior to testing, the birds were divided into three exposure groups: Passive speech exposure (regular exposure to human speech), no speech exposure (completely isolated), and speech-trained (using the Model-Rival Method). After the exposure period, all budgerigars were tested using operant conditioning procedures. Birds were trained to peck keys in response to hearing different synthetic speech sounds that began with either “d” or “t.” Sounds varied in VOT and in the frequency of the first formant. Once training performance reached 80% on the series endpoints, budgerigars were presented with the entire series, including ambiguous sounds. The responses on these trials were used to determine which speech cues the birds use, if cue trading behavior was present, and whether speech exposure had an influence on perception. Preliminary data suggest experience with speech sounds is not necessary for cue trading by budgerigars.
The perceived location of auditory images has been recently studied in budgerigars ͓Dent and Dool... more The perceived location of auditory images has been recently studied in budgerigars ͓Dent and Dooling, J. Acoust. Soc. Am. 113, 2146 -2158 ͑2003͔͒. Those results suggested that budgerigars ͑Melopsittacus undulatus͒ perceive precedence effect stimuli in a manner similar to humans and other animals. Here we extend those experiments to include the effects of intensity on the perceived location of auditory images and the perceived location of paired stimuli from multiple locations in space. We measured the abilities of budgerigars to discriminate between paired stimuli separated in time, intensity, and/or location. Increasing the intensity of a lag stimulus disrupted localization dominance. Budgerigars also perceived simultaneously presented ͑away from the midline͒ stimuli as very similar to a single sound presented from the midline, much like the phantom image reported in humans. The perception of paired stimuli from one side of the head versus two sides of the head was also examined and showed that the spatial cues available in these stimuli are important and that echoes are not perceptually inaccessible during localization dominance conditions. The results from these experiments add further data showing the precedence effect in budgerigars is similar to that found in humans and other animals.
Auditory experiments on the localization of sounds in the presence of reflections, or echoes, tha... more Auditory experiments on the localization of sounds in the presence of reflections, or echoes, that arrive later and from different directions are important to understanding hearing in natural environments. The perceived location of the auditory image can change with the time delay between the presentations of a leading and lagging sound. These changes in perceived location, encompassing the precedence effect, have been examined behaviorally or physiologically in humans and a number of animals. Here, these results are extended to include budgerigars. Behavioral methods were used to measure the discrimination performance between a stimulus presented at ϩ and Ϫ90°azimuth with a delay ͑left-right͒, from the same two stimuli presented with the opposite delay ͑right-left͒. At short delays, where humans experience summing localization, budgerigars have difficulty discriminating between the two presentation types. With increasing delays, where humans experience localization dominance, budgerigars show improved discrimination performance. At even longer delays, where echo thresholds are found in humans, discrimination performance worsens again. The shapes of the discrimination functions are affected by the intensity, locations, and durations of the stimuli, and are subject to a buildup effect. These results show that budgerigars exhibit the phases of the precedence effect similar to humans and other animals.
The detection of signals in noise is important for understanding both the mechanisms of hearing a... more The detection of signals in noise is important for understanding both the mechanisms of hearing and how the auditory system functions under more natural conditions. In humans, the auditory system gains some improvement if the signal and noise are separated in space (binaural masking release). Birds with small heads are at a disadvantage in separating noise and signal sources relative to large mammals, because interaural time differences are much smaller. Two binaural phenomena in budgerigars related to the detection of tones in noise were examined. Budgerigars show 8 dB of free-field binaural masking release when signal and noise are presented to their right side and correlated noise is presented to their left side. Budgerigars also show a spatial masking release of 9 dB when a signal and noise are separated in azimuth by 90 ° . These results are similar to those found in humans and other mammals with much larger heads.
Other than humans, extensive vocal learning has only been widely demonstrated in birds. Moreover,... more Other than humans, extensive vocal learning has only been widely demonstrated in birds. Moreover, there are only a handful of avian species that are known to be good mimics of human speech. One such species is the budgerigar ͑Melopsittacus undulatus͒, which is a popular mimic of human speech and learns new vocalizations throughout adult life. Using operant conditioning procedures with a repeating background task, we tested budgerigars on the discrimination of tokens from two synthetic /ba/-/wa/ speech continua that differed in syllable, but not transition, duration. Budgerigars showed a significant improvement in discrimination performance on both continua near the phonetic boundary for humans. Budgerigars also showed a shift in the location of the phonetic boundary with a change in syllable length, similar to what has been described for humans and other primates. These results on a nonmammalian species provide support for the operation of a general, nonphonetic, auditory process as one mechanism which can lead to the well-known stimulus-length effect in humans.
The Journal of the Acoustical Society of America, 1997
Auditory filter shapes in the budgerigar (Melopsittacus undulatus) derived from notched‐noise mas... more Auditory filter shapes in the budgerigar (Melopsittacus undulatus) derived from notched‐noise maskers. [The Journal of the Acoustical Society of America 101, 3124 (1997)]. Jian‐Yu Lin, Robert J. Dooling, Michael L. Dent. Abstract. ...
Belgian Waterslager (BWS) canaries are characterized by a mean 30% loss of hair cells in the basi... more Belgian Waterslager (BWS) canaries are characterized by a mean 30% loss of hair cells in the basilar papilla compared to other canaries, and a corresponding increase in behavioral auditory thresholds. In spite of the large number of missing and damaged sensory cells, there is on average only a 12% reduction in the number of fibers in the VIIIth nerve. In this study, we examined cell number and size, and volume of auditory nuclei, specifically in nucleus magnocellularis and nucleus laminaris in Belgian Waterslager canaries. While the overall anatomical structure and organization of these nuclei and the total number of cells in the non-BWS and BWS canaries were comparable, BWS canaries showed a significant decrease in the volume of the auditory nuclei that was attributed to a reduction in cell size. These results provide further evidence in favor of a role of the sensory epithelium in the maintenance of central auditory structures. ß 0378-5955 / 02 / $^see front matter ß 2002 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 8 -5 9 5 5 ( 0 1 ) 0 0 3 8 7 -2
The Journal of the Acoustical Society of America, 2008
ABSTRACT Detecting a signal embedded in noise is known to be enhanced by spatially separating the... more ABSTRACT Detecting a signal embedded in noise is known to be enhanced by spatially separating the signal and noise in humans and other animals. This process is known as spatial unmasking and is a part of the larger phenomenon of the cocktail party problem. The exact mechanisms of unmasking are unknown, but binaural processes are thought to be at least partially involved. Most animals that exhibit unmasking are fairly adept at localizing pure tones in space. We wished to study spatial unmasking in an animal that is very poor at sound localization: the zebra finch. Zebra finches were trained using operant conditioning techniques and the psychophysical method of constant stimuli to peck keys for food reinforcement when they detected a tone embedded in a broadband noise masker. Thresholds were obtained for pure tones ranging from 500 Hz to 4000 Hz when the signal and the noise were emitted from the same speaker and when they were emitted from speaker locations separated by 180 deg. Zebra finches showed relatively little unmasking and there was large variation across subjects and frequencies, suggesting that the mechanisms underlying sound localization are related to those that result in spatial unmasking.
The Journal of the Acoustical Society of America, 2010
The present study examined auditory distance perception cues in a non-territorial songbird, the z... more The present study examined auditory distance perception cues in a non-territorial songbird, the zebra finch (Taeniopygia guttata), and in a non-songbird, the budgerigar (Melopsittacus undulatus). Using operant conditioning procedures, three zebra finches and three budgerigars were trained to identify 1-(Near) and 75-m (Far) recordings of three budgerigar contact calls, one male zebra finch song, and one female zebra finch call. Once the birds were trained on these endpoint stimuli, other stimuli were introduced into the operant task. These stimuli included recordings at intermediate distances and artificially altered stimuli simulating changes in overall amplitude, high-frequency attenuation, reverberation, and all three cues combined. By examining distance cues (amplitude, high-frequency attenuation, and reverberation) separately, this study sought to determine which cue was the most salient for the birds. The results suggest that both species could scale the stimuli on a continuum from Near to Far and that amplitude was the most important cue for these birds in auditory distance perception, as in humans and other animals.
Illusions are effective tools for the study of the neural mechanisms underlying perception becaus... more Illusions are effective tools for the study of the neural mechanisms underlying perception because neural responses can be correlated to the physical properties of stimuli and the subject's perceptions. The Franssen illusion (FI) is an auditory spatial illusion evoked by presenting a transient, abrupt tone and a slowly rising, sustained tone of the same frequency simultaneously on opposite sides of the subject. Perception of the FI consists of hearing a single sound, the sustained tone, on the side that the transient was presented. Both subcortical and cortical mechanisms for the FI have been proposed, but, to date, there is no direct evidence for either. The data show that humans and rhesus monkeys perceive the FI similarly. Recordings were taken from single units of the inferior colliculus in the monkey while they indicated the perceived location of sound sources with their gaze. The results show that the transient component of the Franssen stimulus, with a shorter first spike latency and higher discharge rate than the sustained tone, encodes the perception of sound location. Furthermore, the persistent erroneous perception of the sustained stimulus location is due to continued excitation of the same neurons, first activated by the transient, by the sustained stimulus without location information. These results demonstrate for the first time, on a trial-by-trial basis, a correlation between perception of an auditory spatial illusion and a subcortical physiological substrate.
The Journal of the Acoustical Society of America, 2001
ABSTRACT Temporal waveform characteristics differentially affect masking by harmonic complexes in... more ABSTRACT Temporal waveform characteristics differentially affect masking by harmonic complexes in birds and humans. In birds, complexes with relatively flat temporal envelopes are more effective maskers than complexes with highly modulated temporal envelopes. Flat temporal waveforms constructed using positive and negative Schroeder‐phase algorithms result in large masking differences in humans, but little masking difference in birds. This effect may be related to differences in the cochlear phase characteristics in the two species. A psychophysical estimate of the phase characteristic has been reported in humans by finding the phase spectrum of a harmonic masker that produces the least masking. Here we estimated the phase characteristic for zebra finches using operant conditioning methods to measure masked thresholds for tones embedded in harmonic complexes with phases selected according to scaled modifications of the Schroeder algorithm. There was little difference between birds and humans when the scalar was between 0.0 and −1.0 (i.e., negative Schroeder phases), but humans showed less masking than birds when the scalar was positive. These results may reflect a more linear phase characteristic along the avian cochlea. [Work supported by NIH R01 DC00198 and NSRA DC00046.]
Mice are emerging as an important behavioral model for studies of auditory perception and acousti... more Mice are emerging as an important behavioral model for studies of auditory perception and acoustic communication. These mammals frequently produce ultrasonic vocalizations, although the details of how these vocalizations are used for communication are not entirely understood. An important step in determining how they might be differentiating their calls is to measure discrimination and identification of the dimensions of various acoustic stimuli. Here, behavioral operant conditioning methods were employed to assess frequency difference limens for pure tones. We found that their thresholds were similar to those in other rodents but higher than in humans. We also asked mice, in an identification paradigm, whether they would use frequency or duration differences to classify stimuli varying on those two dimensions. We found that the mice classified the stimuli based on frequency rather than duration.
The Journal of the Acoustical Society of America, 2001
The precedence effect (PE) is an auditory spatial illusion where the apparent location of two sou... more The precedence effect (PE) is an auditory spatial illusion where the apparent location of two sounds presented from different spatial locations but separated by a delay is determined primarily by the spatial attributes of the leading stimulus. In this review, we compare previously published psychophysical and physiological experiments on the PE in cats. Also included are data from some new psychophysical studies allowing further comparisons to published physiological results. Psychophysical experiments on the precedence effect (on the PE in cats) in cats have shown that they perceive pairs of auditory stimuli presented from different locations in space in a manner dependent on the interstimulus delay (ISD) between stimuli, similar to humans. The behavior of the cats indicates that they experience the phases of the PE, including summing localization, localization dominance, and the echo threshold. These three phenomena of the PE are elicited on the horizontal and vertical planes using ISDs. Here, we present new psychophysical data showing that the PE can also be elicited on the horizontal plane using interstimulus intensity differences (ISIs) and can be disrupted with conflicting ISDs and ISIs. While neural mechanisms of the PE phenomena are less known, single unit recordings from the inferior colliculus (IC) of anesthetized cats support the hypothesis that the IC is an important neural substrate of the PE. PACS no. 43.64.Tk, 43.66.Pn, 43.80.Lb c S. Hirzel Verlag ¡ EAA 463 ACTA ACUSTICA UNITED WITH ACUSTICA Dent et al.: Studies of the Precedence Effect in Cats Vol. 91 (2005)
Journal of comparative psychology (Washington, D.C. : 1983), Jan 30, 2015
The auditory scene is filled with an array of overlapping acoustic signals, yet relatively little... more The auditory scene is filled with an array of overlapping acoustic signals, yet relatively little work has focused on how animals are able to perceptually isolate different sound sources necessary for survival. Much of the previous work on auditory scene analysis has investigated how sequential pure tone stimuli are perceived, but how temporally overlapping complex communication signals are segregated has been largely ignored. In this study, budgerigars and humans were tested using psychophysical procedures to measure their perception of synchronous, asynchronous, and partially overlapping complex signals, including bird calls and human vowels. Segregation thresholds for complex stimuli were significantly lower than those for pure tone stimuli in both humans and birds. Additionally, a species effect was discovered such that relative to humans, budgerigars required significantly less temporal separation between 2 sounds in order to segregate them. Overall, and similar to previous beh...
The ability of three species of birds to discriminate among selected harmonic complexes with fund... more The ability of three species of birds to discriminate among selected harmonic complexes with fundamental frequencies varying from 50 to 1000 Hz was examined in behavioral experiments. The stimuli were synthetic harmonic complexes with waveform shapes altered by component phase selection, holding spectral and intensive information constant. Birds were able to discriminate between waveforms with randomly selected component phases and those with all components in cosine phase, as well as between positive and negative Schroeder-phase waveforms with harmonic periods as short as 1-2 ms. By contrast, human listeners are unable to make these discriminations at periods less than about 3-4 ms. Electrophysiological measures, including cochlear microphonic and compound action potential measurements to the same stimuli used in behavioral tests, showed differences between birds and gerbils paralleling, but not completely accounting for, the psychophysical differences observed between birds and humans. It appears from these data that birds can hear the fine temporal structure in complex waveforms over very short periods. These data show birds are capable of more precise temporal resolution for complex sounds than is observed in humans and perhaps other mammals. Physiological data further show that at least part of the mechanisms underlying this high temporal resolving power resides at the peripheral level of the avian auditory system.
The cannabinoid receptor 1 (CB1R) is found at several stages in the auditory pathway, but its rol... more The cannabinoid receptor 1 (CB1R) is found at several stages in the auditory pathway, but its role in hearing is unknown. Hearing abilities were measured in CB1R knockout mice and compared to those of wild-type mice. Operant conditioning and the psychophysical Method of Constant Stimuli were used to measure audiograms, gap detection thresholds, and frequency difference limens in trained mice using the same methods and stimuli as in previous experiments. CB1R knockout mice showed deficits at frequencies above 8 kHz in their audiograms relative to wild-type mice. CB1R knockouts showed enhancements for detecting gaps in low-pass noisebursts relative to wild-type mice, but were similar for other noise conditions. Finally, the two groups of mice did not differ in their frequency discrimination abilities as measured by the frequency difference limens task. These experiments suggest that the CB1R is involved in auditory processing and lay the groundwork for future physiological experiments.
Journal of the Acoustical Society of America, 2015
ABSTRACT The current project investigates how experience with human speech can influence speech p... more ABSTRACT The current project investigates how experience with human speech can influence speech perception in budgerigars. Budgerigars are vocal mimics and speech exposure can be tightly controlled in a laboratory setting. The data collected include behavioral responses from 30 budgerigars, tested using a cue-trading paradigm with synthetic speech stimuli. Prior to testing, the birds were divided into three exposure groups: Passive speech exposure (regular exposure to human speech), no speech exposure (completely isolated), and speech-trained (using the Model-Rival Method). After the exposure period, all budgerigars were tested using operant conditioning procedures. Birds were trained to peck keys in response to hearing different synthetic speech sounds that began with either “d” or “t.” Sounds varied in VOT and in the frequency of the first formant. Once training performance reached 80% on the series endpoints, budgerigars were presented with the entire series, including ambiguous sounds. The responses on these trials were used to determine which speech cues the birds use, if cue trading behavior was present, and whether speech exposure had an influence on perception. Preliminary data suggest experience with speech sounds is not necessary for cue trading by budgerigars.
The perceived location of auditory images has been recently studied in budgerigars ͓Dent and Dool... more The perceived location of auditory images has been recently studied in budgerigars ͓Dent and Dooling, J. Acoust. Soc. Am. 113, 2146 -2158 ͑2003͔͒. Those results suggested that budgerigars ͑Melopsittacus undulatus͒ perceive precedence effect stimuli in a manner similar to humans and other animals. Here we extend those experiments to include the effects of intensity on the perceived location of auditory images and the perceived location of paired stimuli from multiple locations in space. We measured the abilities of budgerigars to discriminate between paired stimuli separated in time, intensity, and/or location. Increasing the intensity of a lag stimulus disrupted localization dominance. Budgerigars also perceived simultaneously presented ͑away from the midline͒ stimuli as very similar to a single sound presented from the midline, much like the phantom image reported in humans. The perception of paired stimuli from one side of the head versus two sides of the head was also examined and showed that the spatial cues available in these stimuli are important and that echoes are not perceptually inaccessible during localization dominance conditions. The results from these experiments add further data showing the precedence effect in budgerigars is similar to that found in humans and other animals.
Auditory experiments on the localization of sounds in the presence of reflections, or echoes, tha... more Auditory experiments on the localization of sounds in the presence of reflections, or echoes, that arrive later and from different directions are important to understanding hearing in natural environments. The perceived location of the auditory image can change with the time delay between the presentations of a leading and lagging sound. These changes in perceived location, encompassing the precedence effect, have been examined behaviorally or physiologically in humans and a number of animals. Here, these results are extended to include budgerigars. Behavioral methods were used to measure the discrimination performance between a stimulus presented at ϩ and Ϫ90°azimuth with a delay ͑left-right͒, from the same two stimuli presented with the opposite delay ͑right-left͒. At short delays, where humans experience summing localization, budgerigars have difficulty discriminating between the two presentation types. With increasing delays, where humans experience localization dominance, budgerigars show improved discrimination performance. At even longer delays, where echo thresholds are found in humans, discrimination performance worsens again. The shapes of the discrimination functions are affected by the intensity, locations, and durations of the stimuli, and are subject to a buildup effect. These results show that budgerigars exhibit the phases of the precedence effect similar to humans and other animals.
The detection of signals in noise is important for understanding both the mechanisms of hearing a... more The detection of signals in noise is important for understanding both the mechanisms of hearing and how the auditory system functions under more natural conditions. In humans, the auditory system gains some improvement if the signal and noise are separated in space (binaural masking release). Birds with small heads are at a disadvantage in separating noise and signal sources relative to large mammals, because interaural time differences are much smaller. Two binaural phenomena in budgerigars related to the detection of tones in noise were examined. Budgerigars show 8 dB of free-field binaural masking release when signal and noise are presented to their right side and correlated noise is presented to their left side. Budgerigars also show a spatial masking release of 9 dB when a signal and noise are separated in azimuth by 90 ° . These results are similar to those found in humans and other mammals with much larger heads.
Other than humans, extensive vocal learning has only been widely demonstrated in birds. Moreover,... more Other than humans, extensive vocal learning has only been widely demonstrated in birds. Moreover, there are only a handful of avian species that are known to be good mimics of human speech. One such species is the budgerigar ͑Melopsittacus undulatus͒, which is a popular mimic of human speech and learns new vocalizations throughout adult life. Using operant conditioning procedures with a repeating background task, we tested budgerigars on the discrimination of tokens from two synthetic /ba/-/wa/ speech continua that differed in syllable, but not transition, duration. Budgerigars showed a significant improvement in discrimination performance on both continua near the phonetic boundary for humans. Budgerigars also showed a shift in the location of the phonetic boundary with a change in syllable length, similar to what has been described for humans and other primates. These results on a nonmammalian species provide support for the operation of a general, nonphonetic, auditory process as one mechanism which can lead to the well-known stimulus-length effect in humans.
The Journal of the Acoustical Society of America, 1997
Auditory filter shapes in the budgerigar (Melopsittacus undulatus) derived from notched‐noise mas... more Auditory filter shapes in the budgerigar (Melopsittacus undulatus) derived from notched‐noise maskers. [The Journal of the Acoustical Society of America 101, 3124 (1997)]. Jian‐Yu Lin, Robert J. Dooling, Michael L. Dent. Abstract. ...
Belgian Waterslager (BWS) canaries are characterized by a mean 30% loss of hair cells in the basi... more Belgian Waterslager (BWS) canaries are characterized by a mean 30% loss of hair cells in the basilar papilla compared to other canaries, and a corresponding increase in behavioral auditory thresholds. In spite of the large number of missing and damaged sensory cells, there is on average only a 12% reduction in the number of fibers in the VIIIth nerve. In this study, we examined cell number and size, and volume of auditory nuclei, specifically in nucleus magnocellularis and nucleus laminaris in Belgian Waterslager canaries. While the overall anatomical structure and organization of these nuclei and the total number of cells in the non-BWS and BWS canaries were comparable, BWS canaries showed a significant decrease in the volume of the auditory nuclei that was attributed to a reduction in cell size. These results provide further evidence in favor of a role of the sensory epithelium in the maintenance of central auditory structures. ß 0378-5955 / 02 / $^see front matter ß 2002 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 8 -5 9 5 5 ( 0 1 ) 0 0 3 8 7 -2
The Journal of the Acoustical Society of America, 2008
ABSTRACT Detecting a signal embedded in noise is known to be enhanced by spatially separating the... more ABSTRACT Detecting a signal embedded in noise is known to be enhanced by spatially separating the signal and noise in humans and other animals. This process is known as spatial unmasking and is a part of the larger phenomenon of the cocktail party problem. The exact mechanisms of unmasking are unknown, but binaural processes are thought to be at least partially involved. Most animals that exhibit unmasking are fairly adept at localizing pure tones in space. We wished to study spatial unmasking in an animal that is very poor at sound localization: the zebra finch. Zebra finches were trained using operant conditioning techniques and the psychophysical method of constant stimuli to peck keys for food reinforcement when they detected a tone embedded in a broadband noise masker. Thresholds were obtained for pure tones ranging from 500 Hz to 4000 Hz when the signal and the noise were emitted from the same speaker and when they were emitted from speaker locations separated by 180 deg. Zebra finches showed relatively little unmasking and there was large variation across subjects and frequencies, suggesting that the mechanisms underlying sound localization are related to those that result in spatial unmasking.
The Journal of the Acoustical Society of America, 2010
The present study examined auditory distance perception cues in a non-territorial songbird, the z... more The present study examined auditory distance perception cues in a non-territorial songbird, the zebra finch (Taeniopygia guttata), and in a non-songbird, the budgerigar (Melopsittacus undulatus). Using operant conditioning procedures, three zebra finches and three budgerigars were trained to identify 1-(Near) and 75-m (Far) recordings of three budgerigar contact calls, one male zebra finch song, and one female zebra finch call. Once the birds were trained on these endpoint stimuli, other stimuli were introduced into the operant task. These stimuli included recordings at intermediate distances and artificially altered stimuli simulating changes in overall amplitude, high-frequency attenuation, reverberation, and all three cues combined. By examining distance cues (amplitude, high-frequency attenuation, and reverberation) separately, this study sought to determine which cue was the most salient for the birds. The results suggest that both species could scale the stimuli on a continuum from Near to Far and that amplitude was the most important cue for these birds in auditory distance perception, as in humans and other animals.
Illusions are effective tools for the study of the neural mechanisms underlying perception becaus... more Illusions are effective tools for the study of the neural mechanisms underlying perception because neural responses can be correlated to the physical properties of stimuli and the subject's perceptions. The Franssen illusion (FI) is an auditory spatial illusion evoked by presenting a transient, abrupt tone and a slowly rising, sustained tone of the same frequency simultaneously on opposite sides of the subject. Perception of the FI consists of hearing a single sound, the sustained tone, on the side that the transient was presented. Both subcortical and cortical mechanisms for the FI have been proposed, but, to date, there is no direct evidence for either. The data show that humans and rhesus monkeys perceive the FI similarly. Recordings were taken from single units of the inferior colliculus in the monkey while they indicated the perceived location of sound sources with their gaze. The results show that the transient component of the Franssen stimulus, with a shorter first spike latency and higher discharge rate than the sustained tone, encodes the perception of sound location. Furthermore, the persistent erroneous perception of the sustained stimulus location is due to continued excitation of the same neurons, first activated by the transient, by the sustained stimulus without location information. These results demonstrate for the first time, on a trial-by-trial basis, a correlation between perception of an auditory spatial illusion and a subcortical physiological substrate.
The Journal of the Acoustical Society of America, 2001
ABSTRACT Temporal waveform characteristics differentially affect masking by harmonic complexes in... more ABSTRACT Temporal waveform characteristics differentially affect masking by harmonic complexes in birds and humans. In birds, complexes with relatively flat temporal envelopes are more effective maskers than complexes with highly modulated temporal envelopes. Flat temporal waveforms constructed using positive and negative Schroeder‐phase algorithms result in large masking differences in humans, but little masking difference in birds. This effect may be related to differences in the cochlear phase characteristics in the two species. A psychophysical estimate of the phase characteristic has been reported in humans by finding the phase spectrum of a harmonic masker that produces the least masking. Here we estimated the phase characteristic for zebra finches using operant conditioning methods to measure masked thresholds for tones embedded in harmonic complexes with phases selected according to scaled modifications of the Schroeder algorithm. There was little difference between birds and humans when the scalar was between 0.0 and −1.0 (i.e., negative Schroeder phases), but humans showed less masking than birds when the scalar was positive. These results may reflect a more linear phase characteristic along the avian cochlea. [Work supported by NIH R01 DC00198 and NSRA DC00046.]
Mice are emerging as an important behavioral model for studies of auditory perception and acousti... more Mice are emerging as an important behavioral model for studies of auditory perception and acoustic communication. These mammals frequently produce ultrasonic vocalizations, although the details of how these vocalizations are used for communication are not entirely understood. An important step in determining how they might be differentiating their calls is to measure discrimination and identification of the dimensions of various acoustic stimuli. Here, behavioral operant conditioning methods were employed to assess frequency difference limens for pure tones. We found that their thresholds were similar to those in other rodents but higher than in humans. We also asked mice, in an identification paradigm, whether they would use frequency or duration differences to classify stimuli varying on those two dimensions. We found that the mice classified the stimuli based on frequency rather than duration.
The Journal of the Acoustical Society of America, 2001
The precedence effect (PE) is an auditory spatial illusion where the apparent location of two sou... more The precedence effect (PE) is an auditory spatial illusion where the apparent location of two sounds presented from different spatial locations but separated by a delay is determined primarily by the spatial attributes of the leading stimulus. In this review, we compare previously published psychophysical and physiological experiments on the PE in cats. Also included are data from some new psychophysical studies allowing further comparisons to published physiological results. Psychophysical experiments on the precedence effect (on the PE in cats) in cats have shown that they perceive pairs of auditory stimuli presented from different locations in space in a manner dependent on the interstimulus delay (ISD) between stimuli, similar to humans. The behavior of the cats indicates that they experience the phases of the PE, including summing localization, localization dominance, and the echo threshold. These three phenomena of the PE are elicited on the horizontal and vertical planes using ISDs. Here, we present new psychophysical data showing that the PE can also be elicited on the horizontal plane using interstimulus intensity differences (ISIs) and can be disrupted with conflicting ISDs and ISIs. While neural mechanisms of the PE phenomena are less known, single unit recordings from the inferior colliculus (IC) of anesthetized cats support the hypothesis that the IC is an important neural substrate of the PE. PACS no. 43.64.Tk, 43.66.Pn, 43.80.Lb c S. Hirzel Verlag ¡ EAA 463 ACTA ACUSTICA UNITED WITH ACUSTICA Dent et al.: Studies of the Precedence Effect in Cats Vol. 91 (2005)
Journal of comparative psychology (Washington, D.C. : 1983), Jan 30, 2015
The auditory scene is filled with an array of overlapping acoustic signals, yet relatively little... more The auditory scene is filled with an array of overlapping acoustic signals, yet relatively little work has focused on how animals are able to perceptually isolate different sound sources necessary for survival. Much of the previous work on auditory scene analysis has investigated how sequential pure tone stimuli are perceived, but how temporally overlapping complex communication signals are segregated has been largely ignored. In this study, budgerigars and humans were tested using psychophysical procedures to measure their perception of synchronous, asynchronous, and partially overlapping complex signals, including bird calls and human vowels. Segregation thresholds for complex stimuli were significantly lower than those for pure tone stimuli in both humans and birds. Additionally, a species effect was discovered such that relative to humans, budgerigars required significantly less temporal separation between 2 sounds in order to segregate them. Overall, and similar to previous beh...
The ability of three species of birds to discriminate among selected harmonic complexes with fund... more The ability of three species of birds to discriminate among selected harmonic complexes with fundamental frequencies varying from 50 to 1000 Hz was examined in behavioral experiments. The stimuli were synthetic harmonic complexes with waveform shapes altered by component phase selection, holding spectral and intensive information constant. Birds were able to discriminate between waveforms with randomly selected component phases and those with all components in cosine phase, as well as between positive and negative Schroeder-phase waveforms with harmonic periods as short as 1-2 ms. By contrast, human listeners are unable to make these discriminations at periods less than about 3-4 ms. Electrophysiological measures, including cochlear microphonic and compound action potential measurements to the same stimuli used in behavioral tests, showed differences between birds and gerbils paralleling, but not completely accounting for, the psychophysical differences observed between birds and humans. It appears from these data that birds can hear the fine temporal structure in complex waveforms over very short periods. These data show birds are capable of more precise temporal resolution for complex sounds than is observed in humans and perhaps other mammals. Physiological data further show that at least part of the mechanisms underlying this high temporal resolving power resides at the peripheral level of the avian auditory system.
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Papers by Micheal Dent