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G M Klump

Publications and source records attributed to G M Klump.

At least 19 recordsLinked to original sources
PubMed2001

Release from masking in fluctuating background noise in a songbird's auditory forebrain.

Fluctuations in the ubiquitous masking background noise can be exploited by the vertebrate auditory system to considerably improve signal detection. Here we demonstrate neuronal masking release in amplitude-modulated background noise on the level of the European starling's auditory forebrain, an area that is the analogue of the mammalian primary auditory cortex. Tone-evoked responses in the presence of modulated and unmodulated maskers were recorded in unrestrained birds via radiotelemetry. Based on a rate code, the average amount of neuronal masking release was similar to that observed in a psychoacoustic study on the starling with stimuli confined to a single auditory filter. The results suggest that the neurons exploited predominantly temporal features of the acoustic background to improve signal detection.

Acoustic Stimulation↗
PubMed2001

Signal detection in amplitude-modulated maskers. I. Behavioural auditory thresholds in a songbird.

Vertebrates have evolved mechanisms to exploit amplitude modulations in background noise for improving signal detection. However, the mechanisms underlying this masking release are not yet well understood. Here we present evidence for masking release observed in European starlings (Sturnus vulgaris, Aves) that were trained in a Go/NoGo paradigm to report the detection of a short tone (20 ms) in 100% sinusoidally amplitude-modulated noise maskers (400 ms duration). Maskers centred at the tone frequency were composed of one, three, or five spectrally adjacent noise bands each of auditory filter bandwidth. Envelopes of the masking noise bands were either in-phase (i.e. coherent) or successively phase shifted by 90 degrees (i.e. incoherent). A release from masking of up to 28 dB was observed for detection of signals presented in dips of the envelope of coherent maskers compared with those presented in peaks of coherent maskers and in incoherent maskers. For maskers limited to one auditory filter (i.e. limited to the analysis channel tuned to the test signal) this masking release was about 10 dB less than that observed for maskers allowing a comparison across three or five auditory filters. This indicates that both within-channel cues and across-channel cues are important for signal detection. These behavioural data provide the reference for the study of responses of auditory forebrain neurons in the same species reported in a companion paper [Nieder & Klump (2001) Eur. J. Neurosci., 13, 1033-1044].

Animals↗
PubMed2001

Signal detection in amplitude-modulated maskers. II. Processing in the songbird's auditory forebrain.

In the natural environment, acoustic signals have to be detected in ubiquitous background noise. Temporal fluctuations of background noise can be exploited by the auditory system to enhance signal detection, especially if spectral masking components are coherently amplitude modulated across several auditory channels (a phenomenon called 'comodulation masking release'). In this study of neuronal mechanisms of masking release in the primary auditory forebrain (field L) of awake European starlings (Sturnus vulgaris), we determined and compared neural detection thresholds for 20-ms probe tones presented in a background of sinusoidally amplitude modulated (10-Hz) noise maskers. Responses of a total of 34 multiunit clusters were recorded via radiotelemetry with chronically implanted microelectrodes from unrestrained birds. For maskers consisting of a single noise band centred around the recording site's characteristic frequency, a substantial reduction in detection threshold (21 dB on average) was found when probe tones were presented during envelope dips rather than during envelope peaks. Such effects could also explain results obtained for masking protocols where the on-frequency noise band was presented together with excitatory or inhibitory flanking bands that were either coherently modulated (in-phase) or incoherently modulated (phase-shifted). Generally, masking release for probe tones in maskers with flanking bands extending beyond the frequency range of a cell cluster's excitatory tuning curve was not substantially improved. Only some of the neurophysiological results are in agreement with behavioural data from the same species if only the average population response is considered. A subsample of individual neurons, however, could account for behavioural thresholds.

Acoustic Stimulation↗
PubMed2000

Temporal processing in sensory systems.

The idea that sensory information is represented by the temporal firing patterns of neurons or entire networks, rather than by firing rates measured over long integration times, has recently gained increasing experimental support. A number of mechanisms that help to preserve temporal information in ascending sensory systems have been identified, and the role of inhibition in these processes has been characterized. Furthermore, it has become obvious that temporal processing and the representation of sensory events by temporal spike patterns are highly dependent upon the behavioral state of the animal or experimental subject.

Acoustic Stimulation↗
PubMed1999

Time course of simultaneous masking in the starling's auditory forebrain.

Simultaneous masking of pure tones was studied in the primary auditory forebrain of a songbird species, the European starling (Sturnus vulgaris). The responses of 32 multi-unit clusters in the input layer of the auditory neostriatum (field L2a) were recorded via radiotelemetry from freely moving birds. The probe was a 10-ms tone burst at the units' characteristic-frequency (CF) presented 20 dB above the threshold. The masker was an 80-ms tone burst presented either at the units' CF (excitatory masker) or at a frequency located in inhibitory side-bands (inhibitory masker) of the units' tuning curves. The probe was presented either 3 ms or 63 ms after masker onset. Probes presented at a 3-ms delay were influenced at significantly lower levels of an excitatory masker than probes presented at a 63-ms delay. The mean difference in masker level at the detection thresholds for both probe delays was 8 dB. No difference in masker level was observed for inhibitory-frequency maskers. The observed neural masking effects may be explained by at least four mechanisms: (1) swamping of the probe response by the response to the masker, (2) a reduction of the probe response during neural adaptation of the response to the masker, (3) a reduction of the probe response during side-band inhibition in the central nervous system, and (4) suppression originating in the cochlea.

Acoustic Stimulation↗
PubMed1999

Adjustable frequency selectivity of auditory forebrain neurons recorded in a freely moving songbird via radiotelemetry.

One of the hearing system's basic properties that determines the detection of signals is its frequency selectivity. In the natural environment, a songbird may achieve an improved detection ability if the neuronal filters of its auditory system could be sharpened to adapt to the spectrum of the background noise. To address this issue, we studied 35 multi-unit clusters in the input layer of the primary auditory forebrain of nine European starlings (Sturnus vulgaris). Microelectrodes were chronically implanted in this songbird's cortex analogue and the neuronal activity was transmitted from unrestrained birds via a miniature FM transmitter. Frequency tuning curves (FTCs) and inhibitory sidebands were determined by presenting a matrix of frequency-level combinations of pure tones. From each FTC, the characteristic frequency (CF) and several parameters describing the neurons' filter characteristics were derived and compared to the same recording site's filter function while simultaneously stimulating with a continuous CF tone 20 dB above the response threshold. Our results show a significant improvement of frequency selectivity during two-tone stimulation, indicating that spectral filtering in the starling's auditory forebrain depends on the acoustic background in which a signal is presented. Moreover, frequency selectivity was found to be a function of the time over which the stimulus persisted, since FTCs were much sharper and inhibitory sidebands were largely expanded several milliseconds after response onset. Neuronal filter bandwidths during two-tone stimulation in the auditory forebrain are in good agreement with psychoacoustically measured critical bandwidths in the same species. Radiotelemetry proved to be a powerful tool in studying neuronal activity in freely behaving birds.

Acoustic Stimulation↗
PubMed1995

Discrimination training in a GO/NOGO-procedure alters the 2-deoxyglucose pattern in the Starling's forebrain.

European starling's (Sturnus vulgaris L.) were used to measure differences in the glucose metabolism in the auditory forebrain between birds performing an auditory discrimination task and birds habituated to the same acoustic stimuli. One group (n = 5) of individuals was trained in an operant GO/NOGO-procedure to report 1-kHz tone signals in a background of 4-kHz stimuli. The other group (n = 5) was habituated to the experimental set-up and to the same sequence of tones presented to the trained birds. [14C]2-deoxyglucose (2DG) uptake was determined in the caudal auditory telencephalon and the nucleus ovoidalis of well trained and habituated birds by autoradiography of brain sections. The tissue areas having grey values above predefined threshold values of labelling were determined in every brain section of each bird and then combined to volumes of labelled tissue. No significant differences of the 2DG uptake in the nucleus ovoidalis were found between the two experimental groups. In the caudal auditory telencephalon, however, significant differences in 2DG-labelling were found. In the trained birds, the labelling in the caudal auditory telencephalon was confined to smaller brain regions than in the habituated birds. These results suggest a differential processing of sounds in the trained and habituated birds which is discussed in the context of sharpening of the frequency representation by GABAergic inhibition and processes of attention.

Acoustic Stimulation↗
PubMed1995

Peripheral basis for the auditory deficit in Belgian Waterslager canaries (Serinus canarius).

Recently, behavioural thresholds obtained in canaries of the Belgian Waterslager strain showed that these birds have an inherited auditory deficit. Canaries of this strain have absolute auditory thresholds at frequencies above 2.0 kHz that are as much as 40 dB above the threshold of canaries of other strains. We obtained audiograms from cochlear microphonics and from compound action potentials from the 8th nerve of Waterslager and non-Waterslager canaries and compare these results to previous behavioural data on hearing in this species. We also examined the growth of evoked potential amplitude-intensity functions in Waterslager and non-Waterslager canaries. Together with reflectance measurements of middle-ear function from both Waterslager and non-Waterslager canaries, we conclude that the origin of auditory deficit in Waterslager canaries lies in the cochlea.

Acoustic Stimulation↗
PubMed1995

Temporal modulation transfer functions in the European Starling (Sturnus vulgaris): II. Responses of auditory-nerve fibres.

The temporal resolution of cochlear-nerve fibres in the European starling was determined with sinusoidally amplitude-modulated noise stimuli similar to those previously used in a psychoacoustic study in this species (Klump and Okanoya, 1991). Temporal modulation transfer curves (TMTFs) were constructed for cochlear afferents allowing a direct comparison with the starling's behavioural performance. On average, the neuron's detection of modulation was less sensitive than that obtained in the behavioural experiments, although the most sensitive cells approached the values determined psychophysically. The shapes of the neural TMTFs generally resembled low-pass or band-pass filter functions, and the shapes of the averaged neural functions were very similar to those obtained in the behavioural study for two different types of stimuli (gated and continuous carrier). Minimum integration times calculated from the upper cut-off frequency of the neural TMTFs had a median of 0.97 ms with a range of 0.25 to 15.9 ms. The relations between the minimum integration times and the tuning characteristics of the cells (tuning curve bandwidth, Q10 dB-value, high- and low-frequency slopes of the tuning curves) are discussed. Finally, we compare the TMTF data recorded in the starling auditory nerve with data from neurophysiological and behavioural observations on temporal resolution using other experimental paradigms in this and other vertebrate species.

Acoustic Stimulation↗
PubMed1995

Critical bands and critical-ratio bandwidth in the European starling.

Critical bands (CB) and critical-ratio (CR) bandwidth were determined in five European starlings (Sturnus vulgaris) using a GO/NOGO procedure and the method of constant stimuli. Test-tone frequencies were 1, 2, 4, and 6.3 kHz. Critical ratios were independent of the level of the white noise masker. The lowest CR of 21.8 dB was found at 1 kHz, and the CR monotonically increased on average by 2.3 dB per octave. CR-bandwidths at a masker spectrum level of 41 dB were 151, 191, 437, and 501 Hz at 1, 2, 4, and 6.3 kHz, respectively. With the exception of the test-tone frequency of 6.3 kHz, the size of the critical bands measured with a band-narrowing procedure was similar to that of the CR-bandwidth. CBs were 135, 233, 345, and 1156 Hz at 1, 2, 4, and 6.3 kHz, respectively. A repeat measurement at 6.3 kHz with another speaker position yielded a CB of 860 Hz. The results of this psychoacoustic study in the starling are discussed with respect to comparative data from other vertebrates and to neurophysiological bandwidth measurements of tuning curves of auditory-nerve fibres.

Acoustic Stimulation↗
PubMed1995

Comodulation masking release in a songbird.

Comodulation masking release (CMR) describes the reduced masking of a pure tone when the masking is a noise that is coherently amplitude modulated (comodulated) over the total range of the spectrum compared to masking by an unmodulated noise of the same bandwidth and overall energy. The masking release results from cues available within a critical band and from cues generated by comparisons across critical bands ('true' CMR). Here we report data on masking release and 'true' CMR in a songbird, the European starling (Strunus vulgaris), that was demonstrated in a psychoacoustic experiment using a GO/NOGO paradigm. Masked thresholds for 2-kHz tones centered in digitally generated continuous masking noise of different bandwidths were determined, and the amount of masking release was calculated as the threshold difference between the unmodulated and the comodulated condition. In the first experiment the modulator was a 50-Hz lowpass noise. A masking release of 11.8 dB was found for the noise masker with the largest bandwidth (1600 Hz). With the masker bandwidth decreasing to 50 Hz, the birds' release from masking was reduced to 1.6 dB. The starling's 'true' CMR was 4 dB or 8 dB, depending on the definition that was applied. In a second experiment the masker bandwidth was constant (1600 Hz) and the cut-off frequency of the modulator was varied. A release from masking of 17.8 dB was found for a modulator cut-off frequency of 12.5 Hz. It decreased to 6.1 dB with an increase in the modulator cut-off frequency to 400 Hz. The duration of the test signal (100-750 ms) had little effect on the release from masking. Given the similarities in the release from masking and in CMR of starlings and humans, the starling may provide an excellent model for studying the mechanisms that underlie the generation of CMR.

Acoustic Stimulation↗
PubMed1995

An excitation-pattern model for the starling (Sturnus vulgaris).

This paper develops and tests an excitation-pattern model for the starling. Like excitation-pattern models for humans [e.g., Zwicker, Acustica 6, 365-381 (1956); Florentine and Buus, J. Acoust. Soc. Am. 70, 1646-1654 (1981)], the model for starlings provides a unified account of a large body of data. The foundation of the model is a critical-band scale, which is derived as an equal-distance scale according to a cochlear-map function. The cochlear-map function is determined as a best-fitting function to physiological data relating characteristic frequency (CF) of auditory-nerve fibers to their place of innervation on the basilar papilla. Excitation patterns are derived from auditory-nerve measurements of levels at CF necessary to produce firing rates equal to those evoked by a test tone. The shape of these excitation patterns is independent of level and frequency when plotted on a cochlear-distance scale. The resulting model indicates that 10-dB bandwidths of auditory-nerve tuning curves and frequency DLs can be approximated as equal distances along the basilar papilla. Predictions of level discrimination are in good agreement with the data, except below 20 dB SL. Overall, the present work indicates that excitation-pattern models account for a wide range of auditory phenomena in both humans and starlings, when the models take into account differences in critical-band scales, absolute thresholds, excitation-pattern slopes, and growth of excitation, which is linear in starlings, but nonlinear in humans.

Animals↗
PubMed1995

[Indications of continuous hair cell regeneration in a song bird with genetically-induced cochlear hearing loss].

In recent years evidence has accumulated that birds in contrast to mammals have a great capacity to replace lost hair cells after cochlear trauma. Despite this capacity for cochlear repair, a hereditary hearing deficit for frequencies above 2 kHz has been described in a peculiar strain of canaries (Belgian Water-slagers). Because previous thresholds were determined by psychophysical methods, the origin of the hearing loss could not be identified. In order to determine if this loss originated in the cochlea and if these birds lack the potential for hair cell regeneration, we carried out physiological and morphological analyses of the hearing organ. Our results showed that most of the hair cells displayed severe pathologies. Also, found were small, microvilli-covered cells that resembled forms described during normal hair cell development. Small microvilli-covered cells with small sterovillar bundles have been described as regenerating hair cells in other birds after severe cochlear insults. These observations indicate that adult Belgian Waterslager canaries continuously produce new cochlear hair cells. They do not, however, succeed in reforming a normal basilar papilla. We believe that these birds are a promising model for future studies of cochlear hair cell repair mechanisms.

Animals↗
PubMed1992

Azimuthal sound localization in the European starling (Sturnus vulgaris): I. Physical binaural cues.

The physical measurements reported here test whether the European starling (Sturnus vulgaris) evaluates the azimuth direction of a sound source with a peripheral auditory system composed of two acoustically coupled pressure-difference receivers (1) or of two decoupled pressure receivers (2). A directional pattern of sound intensity in the free-field was measured at the entrance of the auditory meatus using a probe microphone, and at the tympanum using laser vibrometry. The maximum differences in the sound-pressure level measured with the microphone between various speaker positions and the frontal speaker position were 2.4 dB at 1 and 2 kHz, 7.3 dB at 4 kHz, 9.2 dB at 6 kHz, and 10.9 dB at 8 kHz. The directional amplitude pattern measured by laser vibrometry did not differ from that measured with the microphone. Neither did the directional pattern of travel times to the ear. Measurements of the amplitude and phase transfer function of the starling's interaural pathway using a closed sound system were in accord with the results of the free-field measurements. In conclusion, although some sound transmission via the interaural canal occurred, the present experiments support the hypothesis 2 above that the starling's peripheral auditory system is best described as consisting of two functionally decoupled pressure receivers.

Acoustic Stimulation↗
PubMed1992

Frequency discrimination in the European starling (Sturnus vulgaris): a comparison of different measures.

Frequency-difference limens (DL) were determined in a songbird, the European starling (Sturnus vulgaris), for stimuli differing in the type of frequency change. Four different types of frequency change were studied: an increase in frequency between pulsed tones (type FSU), a single sinusoidal sweep upward (type SSU) starting in the center of an 800 ms signal, an asymmetrical periodic sinusoidal frequency modulation that extended only above the reference frequency (type ASFM), and a symmetrical periodical sinusoidal frequency modulation extending to both sides of the reference frequency (type SSFM). Frequency DLs at two reference frequencies, 1 and 4 kHz, were studied. At 1 kHz, the starling showed the lowest DL for pulsed tones (11.4 Hz), slightly higher DLs for single sweeps and asymmetrical frequency modulation at modulation frequencies of < or = 40 Hz (15.9 Hz for stimulus SSU, and 15.3 Hz for low modulation frequencies of stimulus type ASFM). At a reference frequency of 1 kHz, the DL for symmetrical modulation (type SSFM) at modulation frequencies < or = 40 Hz was about twice as large (21.6 Hz) than for pulsed tones. Furthermore, the DLs for periodically modulated signals at a modulation frequency of 320 Hz were about twice as large as those at low modulation frequencies. At a reference frequency of 4 kHz, the differences in the DLs for various stimulus types were insignificant (27.7 Hz for type FSU, 23.3 Hz for type SSU, 28.0 Hz for type ASFM and low modulation frequencies, and 24.6 Hz for type SSFM and low modulation frequencies). Only at high modulation frequencies (> or = 320 Hz) were the DLs increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1992

Auditory perception of conspecific and heterospecific vocalizations in birds: evidence for special processes.

Budgerigars (Melopsittacus undulatus), canaries (Serinus canaria), and zebra finches (Poephila guttata castanotis) were tested for their ability to discriminate among distance calls of each species. For comparison, starlings (Sturnus vulgaris) were tested on the same sounds. Response latencies to detect a change in a repeating background of sound were taken as a measure of the perceptual similarity among calls. All 4 species showed clear evidence of 3 perceptual categories corresponding to the calls of the 3 species. Also, budgerigars, canaries, and zebra finches showed an enhanced ability to discriminate among calls of their own species over the calls of the others. Starlings discriminated more efficiently among canary calls than among budgerigar or zebra finch calls. The results show species differences in discrimination of species-specific acoustic communication signals and provide insight into the nature of specialized perceptual processes.

Animal Communication↗
PubMed1991

Temporal modulation transfer functions in the European starling (Sturnus vulgaris): I. Psychophysical modulation detection thresholds.

Temporal modulation transfer functions (TMTF) were obtained from four European starlings (Sturnus vulgaris) using a psychophysical Go/NoGo procedure combined with the method of constant stimuli. The TMTF for a continuous, broad-band noise of 55 dB SPL had a low-pass characteristic with a cut-off frequency of 123 Hz. For an 800 ms gated stimulus of the same sound-pressure level, the TMTF had the shape of a band-pass filter with the most sensitive modulation frequency at around 20 Hz. At 75 dB the band-pass shape of the TMTF was preserved, whereas at 35 dB SPL the TMTF had a low-pass characteristic. The cut-off frequency of the TMTF for continuous noise depends on which part of the spectrum carries the information on the envelope fluctuations. If only sound energy below 1 or 1.5 kHz is modulated, then the cut-off frequencies are 40 and 38 Hz, respectively. If only sound above 3 kHz carries the information on the modulation, then the cut-off frequency is 125 Hz and the shape of the TMTF is similar to that found for broadband noise. The results are discussed with respect to the coding of sinusoidal amplitude modulations by the auditory system and to different measures of time, frequency and intensity resolution in the starling.

Acoustic Stimulation↗