American mink (Neovison vison) kits are born altricial and fully dependent on maternal care, for ... more American mink (Neovison vison) kits are born altricial and fully dependent on maternal care, for which the kits' vocalizations appear essential. We used auditory brainstem responses (ABRs) to determine: (1) hearing sensitivity of adult females from two breeding lines known to differ in maternal behaviour and (2) development of hearing in kits 8-52 days of age. We also studied sound production in 20 kits throughout postnatal days 1 to 44. Adult female mink had a broad hearing range from 1 kHz to above 70 kHz, with peak sensitivity (threshold of 20 dB SPL) at 8-10 kHz, and no difference in sensitivity between the two breeding lines (P>0.22) to explain the difference in maternal care. Mink kits showed no signs of hearing up to postnatal day 24. From day 30, all kits had ABRs indicative of hearing. Hearing sensitivity increased with age, but was still below the adult level at postnatal day 52. When separated from their mothers, kits vocalized loudly. Until the age of 22 days, 90% of all kits vocalized with no significant decline with age (P=0.27). From day 25, concurrent with the start of hearing, the number of vocalizing kits decreased with age (P<0.001), in particular in kits that were re-tested (P=0.004). Large numbers of mink are kept in fur industry farms, and our results are important to the understanding of sound communication, which is part of their natural behaviour. Our results also suggest mink as an interesting model for studying the development of mammalian hearing and its correlation to sound production.
... Page 132. 118 RA Jørgensen et al. Light Light . 1.2. 3.4. ... All statisti-cal tests were per... more ... Page 132. 118 RA Jørgensen et al. Light Light . 1.2. 3.4. ... All statisti-cal tests were performed in SAS (Version 9.1 for Windows, SAS Institute, Inc., Cary, NC), with a significance level at a= 0.05. Page 133. 119 Importance of Hearing for Survival of Danio rerio (Zebrafish)… Fig. ...
Neuropeptide PDF (pigment-dispersing factor)-secreting large ventrolateral neurons (lLN(v)s) in t... more Neuropeptide PDF (pigment-dispersing factor)-secreting large ventrolateral neurons (lLN(v)s) in the Drosophila brain regulate daily patterns of rest and arousal. These bilateral wake-promoting neurons are light responsive and integrate information from the circadian system, sleep circuits, and light environment. To begin to dissect the synaptic circuitry of the circadian neural network, we performed simultaneous dual whole-cell patch-clamp recordings of pairs of lLN(v)s. Both ipsilateral and contralateral pairs of lLN(v)s exhibit synchronous rhythmic membrane activity with a periodicity of ∼ 5-10 s. This rhythmic lLN(v) activity is blocked by TTX, voltage-gated sodium blocker, or α-bungarotoxin, nicotinic acetylcholine receptor antagonist, indicating that action potential-dependent cholinergic synaptic connections are required for rhythmic lLN(v) activity. Since injecting current into one neuron of the pair had no effect on the membrane activity of the other neuron of the pair, this suggests that the synchrony is attributable to bilateral inputs and not coupling between the pairs of lLN(v)s. To further elucidate the nature of these synaptic inputs to lLN(v)s, we blocked or activated a variety of neurotransmitter receptors and measured effects on network activity and ionic conductances. These measurements indicate the lLN(v)s possess excitatory nicotinic ACh receptors, inhibitory ionotropic GABA(A) receptors, and inhibitory ionotropic GluCl (glutamate-gated chloride) receptors. We demonstrate that cholinergic input, but not GABAergic input, is required for synchronous membrane activity, whereas GABA can modulate firing patterns. We conclude that neuropeptidergic lLN(v)s that control rest and arousal receive synchronous synaptic inputs mediated by ACh.
Physiological and anatomical studies have suggested that alligators have unique adaptations for s... more Physiological and anatomical studies have suggested that alligators have unique adaptations for spatial hearing. Sound localization cues are primarily generated by the filtering of sound waves by the head. Different vertebrate lineages have evolved external and/or internal anatomical adaptations to enhance these cues, such as pinnae and interaural canals. It has been hypothesized that in alligators, directionality may be enhanced via the acoustic coupling of middle ear cavities, resulting in a pressure difference receiver (PDR) mechanism. The experiments reported here support a role for a PDR mechanism in alligator sound localization by demonstrating that (1) acoustic space cues generated by the external morphology of the animal are not sufficient to generate location cues that match physiological sensitivity, (2) continuous pathways between the middle ears are present to provide an anatomical basis for coupling, (3) the auditory brainstem response shows some directionality, and (4) eardrum movement is directionally sensitive. Together, these data support the role of a PDR mechanism in crocodilians and further suggest this mechanism is a shared archosaur trait, most likely found also in the extinct dinosaurs.
Snakes lack both an outer ear and a tympanic middle ear, which in most tetrapods provide impedanc... more Snakes lack both an outer ear and a tympanic middle ear, which in most tetrapods provide impedance matching between the air and inner ear fluids and hence improve pressure hearing in air. Snakes would therefore be expected to have very poor pressure hearing and generally be insensitive to airborne sound, whereas the connection of the middle ear bone to the jaw bones in snakes should confer acute sensitivity to substrate vibrations. Some studies have nevertheless claimed that snakes are quite sensitive to both vibration and sound pressure. Here we test the two hypotheses that: (1) snakes are sensitive to sound pressure and (2) snakes are sensitive to vibrations, but cannot hear the sound pressure per se. Vibration and sound-pressure sensitivities were quantified by measuring brainstem evoked potentials in 11 royal pythons, Python regius. Vibrograms and audiograms showed greatest sensitivity at low frequencies of 80-160Hz, with sensitivities of -54dBre.1ms -2 and 78dBre.20mPa, respectively. To investigate whether pythons detect sound pressure or sound-induced head vibrations, we measured the sound-induced head vibrations in three dimensions when snakes were exposed to sound pressure at threshold levels. In general, head vibrations induced by threshold-level sound pressure were equal to or greater than those induced by threshold-level vibrations, and therefore sound-pressure sensitivity can be explained by sound-induced head vibration. From this we conclude that pythons, and possibly all snakes, lost effective pressure hearing with the complete reduction of a functional outer and middle ear, but have an acute vibration sensitivity that may be used for communication and detection of predators and prey.
To create a user-operated pure-tone audiometry method based on the method of maximum likelihood (... more To create a user-operated pure-tone audiometry method based on the method of maximum likelihood (MML) and the two-alternative forced-choice (2AFC) paradigm with high test-retest reliability without the need of an external operator and with minimal influence of subjects' fluctuating response criteria. User-operated audiometry was developed as an alternative to traditional audiometry for research purposes among musicians. Test-retest reliability of the user-operated audiometry system was evaluated and the user-operated audiometry system was compared with traditional audiometry. Test-retest reliability of user-operated 2AFC audiometry was tested with 38 naïve listeners. User-operated 2AFC audiometry was compared to traditional audiometry in 41 subjects. The repeatability of user-operated 2AFC audiometry was comparable to traditional audiometry with standard deviation of differences from 3.9 dB to 5.2 dB in the frequency range of 250-8000 Hz. User-operated 2AFC audiometry gave thresholds 1-2 dB lower at most frequencies compared to traditional audiometry. User-operated 2AFC audiometry does not require specific operating skills and the repeatability is acceptable and similar to traditional audiometry. User operated 2AFC audiometry is a reliable alternative to traditional audiometry.
Lungfishes are the closest living relatives of the tetrapods, and the ear of recent lungfishes re... more Lungfishes are the closest living relatives of the tetrapods, and the ear of recent lungfishes resembles the tetrapod ear more than the ear of ray-finned fishes and is therefore of interest for understanding the evolution of hearing in the early tetrapods. The water-to-land transition resulted in major changes in the tetrapod ear associated with the detection of air-borne sound pressure, as evidenced by the late and independent origins of tympanic ears in all of the major tetrapod groups. To investigate lungfish pressure and vibration detection, we measured the sensitivity and frequency responses of five West African lungfish (Protopterus annectens) using brainstem potentials evoked by calibrated sound and vibration stimuli in air and water. We find that the lungfish ear has good low-frequency vibration sensitivity, like recent amphibians, but poor sensitivity to air-borne sound. The skull shows measurable vibrations above 100 Hz when stimulated by air-borne sound, but the ear is apparently insensitive at these frequencies, suggesting that the lungfish ear is neither adapted nor pre-adapted for aerial hearing. Thus, if the lungfish ear is a model of the ear of early tetrapods, their auditory sensitivity was limited to very low frequencies on land, mostly mediated by substrate-borne vibrations.
American mink (Neovison vison) kits are born altricial and fully dependent on maternal care, for ... more American mink (Neovison vison) kits are born altricial and fully dependent on maternal care, for which the kits' vocalizations appear essential. We used auditory brainstem responses (ABRs) to determine: (1) hearing sensitivity of adult females from two breeding lines known to differ in maternal behaviour and (2) development of hearing in kits 8-52 days of age. We also studied sound production in 20 kits throughout postnatal days 1 to 44. Adult female mink had a broad hearing range from 1 kHz to above 70 kHz, with peak sensitivity (threshold of 20 dB SPL) at 8-10 kHz, and no difference in sensitivity between the two breeding lines (P>0.22) to explain the difference in maternal care. Mink kits showed no signs of hearing up to postnatal day 24. From day 30, all kits had ABRs indicative of hearing. Hearing sensitivity increased with age, but was still below the adult level at postnatal day 52. When separated from their mothers, kits vocalized loudly. Until the age of 22 days, 90% of all kits vocalized with no significant decline with age (P=0.27). From day 25, concurrent with the start of hearing, the number of vocalizing kits decreased with age (P<0.001), in particular in kits that were re-tested (P=0.004). Large numbers of mink are kept in fur industry farms, and our results are important to the understanding of sound communication, which is part of their natural behaviour. Our results also suggest mink as an interesting model for studying the development of mammalian hearing and its correlation to sound production.
... Page 132. 118 RA Jørgensen et al. Light Light . 1.2. 3.4. ... All statisti-cal tests were per... more ... Page 132. 118 RA Jørgensen et al. Light Light . 1.2. 3.4. ... All statisti-cal tests were performed in SAS (Version 9.1 for Windows, SAS Institute, Inc., Cary, NC), with a significance level at a= 0.05. Page 133. 119 Importance of Hearing for Survival of Danio rerio (Zebrafish)… Fig. ...
Neuropeptide PDF (pigment-dispersing factor)-secreting large ventrolateral neurons (lLN(v)s) in t... more Neuropeptide PDF (pigment-dispersing factor)-secreting large ventrolateral neurons (lLN(v)s) in the Drosophila brain regulate daily patterns of rest and arousal. These bilateral wake-promoting neurons are light responsive and integrate information from the circadian system, sleep circuits, and light environment. To begin to dissect the synaptic circuitry of the circadian neural network, we performed simultaneous dual whole-cell patch-clamp recordings of pairs of lLN(v)s. Both ipsilateral and contralateral pairs of lLN(v)s exhibit synchronous rhythmic membrane activity with a periodicity of ∼ 5-10 s. This rhythmic lLN(v) activity is blocked by TTX, voltage-gated sodium blocker, or α-bungarotoxin, nicotinic acetylcholine receptor antagonist, indicating that action potential-dependent cholinergic synaptic connections are required for rhythmic lLN(v) activity. Since injecting current into one neuron of the pair had no effect on the membrane activity of the other neuron of the pair, this suggests that the synchrony is attributable to bilateral inputs and not coupling between the pairs of lLN(v)s. To further elucidate the nature of these synaptic inputs to lLN(v)s, we blocked or activated a variety of neurotransmitter receptors and measured effects on network activity and ionic conductances. These measurements indicate the lLN(v)s possess excitatory nicotinic ACh receptors, inhibitory ionotropic GABA(A) receptors, and inhibitory ionotropic GluCl (glutamate-gated chloride) receptors. We demonstrate that cholinergic input, but not GABAergic input, is required for synchronous membrane activity, whereas GABA can modulate firing patterns. We conclude that neuropeptidergic lLN(v)s that control rest and arousal receive synchronous synaptic inputs mediated by ACh.
Physiological and anatomical studies have suggested that alligators have unique adaptations for s... more Physiological and anatomical studies have suggested that alligators have unique adaptations for spatial hearing. Sound localization cues are primarily generated by the filtering of sound waves by the head. Different vertebrate lineages have evolved external and/or internal anatomical adaptations to enhance these cues, such as pinnae and interaural canals. It has been hypothesized that in alligators, directionality may be enhanced via the acoustic coupling of middle ear cavities, resulting in a pressure difference receiver (PDR) mechanism. The experiments reported here support a role for a PDR mechanism in alligator sound localization by demonstrating that (1) acoustic space cues generated by the external morphology of the animal are not sufficient to generate location cues that match physiological sensitivity, (2) continuous pathways between the middle ears are present to provide an anatomical basis for coupling, (3) the auditory brainstem response shows some directionality, and (4) eardrum movement is directionally sensitive. Together, these data support the role of a PDR mechanism in crocodilians and further suggest this mechanism is a shared archosaur trait, most likely found also in the extinct dinosaurs.
Snakes lack both an outer ear and a tympanic middle ear, which in most tetrapods provide impedanc... more Snakes lack both an outer ear and a tympanic middle ear, which in most tetrapods provide impedance matching between the air and inner ear fluids and hence improve pressure hearing in air. Snakes would therefore be expected to have very poor pressure hearing and generally be insensitive to airborne sound, whereas the connection of the middle ear bone to the jaw bones in snakes should confer acute sensitivity to substrate vibrations. Some studies have nevertheless claimed that snakes are quite sensitive to both vibration and sound pressure. Here we test the two hypotheses that: (1) snakes are sensitive to sound pressure and (2) snakes are sensitive to vibrations, but cannot hear the sound pressure per se. Vibration and sound-pressure sensitivities were quantified by measuring brainstem evoked potentials in 11 royal pythons, Python regius. Vibrograms and audiograms showed greatest sensitivity at low frequencies of 80-160Hz, with sensitivities of -54dBre.1ms -2 and 78dBre.20mPa, respectively. To investigate whether pythons detect sound pressure or sound-induced head vibrations, we measured the sound-induced head vibrations in three dimensions when snakes were exposed to sound pressure at threshold levels. In general, head vibrations induced by threshold-level sound pressure were equal to or greater than those induced by threshold-level vibrations, and therefore sound-pressure sensitivity can be explained by sound-induced head vibration. From this we conclude that pythons, and possibly all snakes, lost effective pressure hearing with the complete reduction of a functional outer and middle ear, but have an acute vibration sensitivity that may be used for communication and detection of predators and prey.
To create a user-operated pure-tone audiometry method based on the method of maximum likelihood (... more To create a user-operated pure-tone audiometry method based on the method of maximum likelihood (MML) and the two-alternative forced-choice (2AFC) paradigm with high test-retest reliability without the need of an external operator and with minimal influence of subjects' fluctuating response criteria. User-operated audiometry was developed as an alternative to traditional audiometry for research purposes among musicians. Test-retest reliability of the user-operated audiometry system was evaluated and the user-operated audiometry system was compared with traditional audiometry. Test-retest reliability of user-operated 2AFC audiometry was tested with 38 naïve listeners. User-operated 2AFC audiometry was compared to traditional audiometry in 41 subjects. The repeatability of user-operated 2AFC audiometry was comparable to traditional audiometry with standard deviation of differences from 3.9 dB to 5.2 dB in the frequency range of 250-8000 Hz. User-operated 2AFC audiometry gave thresholds 1-2 dB lower at most frequencies compared to traditional audiometry. User-operated 2AFC audiometry does not require specific operating skills and the repeatability is acceptable and similar to traditional audiometry. User operated 2AFC audiometry is a reliable alternative to traditional audiometry.
Lungfishes are the closest living relatives of the tetrapods, and the ear of recent lungfishes re... more Lungfishes are the closest living relatives of the tetrapods, and the ear of recent lungfishes resembles the tetrapod ear more than the ear of ray-finned fishes and is therefore of interest for understanding the evolution of hearing in the early tetrapods. The water-to-land transition resulted in major changes in the tetrapod ear associated with the detection of air-borne sound pressure, as evidenced by the late and independent origins of tympanic ears in all of the major tetrapod groups. To investigate lungfish pressure and vibration detection, we measured the sensitivity and frequency responses of five West African lungfish (Protopterus annectens) using brainstem potentials evoked by calibrated sound and vibration stimuli in air and water. We find that the lungfish ear has good low-frequency vibration sensitivity, like recent amphibians, but poor sensitivity to air-borne sound. The skull shows measurable vibrations above 100 Hz when stimulated by air-borne sound, but the ear is apparently insensitive at these frequencies, suggesting that the lungfish ear is neither adapted nor pre-adapted for aerial hearing. Thus, if the lungfish ear is a model of the ear of early tetrapods, their auditory sensitivity was limited to very low frequencies on land, mostly mediated by substrate-borne vibrations.
Uploads
Papers by Christian Brandt