Effects of Midazolam on Food Intake in Budgerigars (Melopsittacus undulatus).

Currently, drug-induced stimulation of appetite is not commonly performed in hyporexic or anorexic companion psittacine birds. Instead, to prevent a catabolic state and weight loss, supplemental feedings are routinely performed by crop gavage. However, crop gavage is not without complications and is stressful to the patient and labor intensive. The objective of this study was to evaluate the effect of midazolam on food intake in healthy budgerigars. In a randomized, blinded, controlled study, change in food intake after intramuscular administration of midazolam (1 mg/kg) or a placebo-control treatment (0.9% saline) was evaluated in 12 healthy adult budgerigars (Melopsittacus undulatus). Food intake was quantified for 1 hour before and after drug administration. Birds were monitored for feeding behavior as well as signs of sedation. After midazolam administration, a median 6-fold (1.1-28) increase in food intake was recorded. In 3 of 6 (50%) birds, the food intake increase after midazolam administration was >10-fold (median 17-fold [10-28]), whereas in the remaining 3 birds, food intake increased by only 1.7-fold (1.1-1.8). The median amount of food ingested (16.7 g/kg [3.2-43.2 g/kg]) was significantly higher after midazolam administration compared with the control group (1.9 g/kg [0.0-19.7 g/kg], P = .015). The median time birds spent displaying feeding behavior after the midazolam injection was 18% (0-43%), compared with 1% (0-20%) in the control group after saline injection. Five of 6 (83%) birds showed signs consistent with mild sedation after midazolam administration. This study demonstrates that midazolam is an appetite stimulant in budgerigars. Future studies are needed to evaluate whether midazolam's effects on food intake are dose dependent and whether the duration of effect exceeds 1 hour.

Midbrain-Level Neural Correlates of Behavioral Tone-in-Noise Detection: Dependence on Energy and Envelope Cues.

Hearing in noise is a problem often assumed to depend on encoding of energy level by channels tuned to target frequencies, but few studies have tested this hypothesis. The present study examined neural correlates of behavioral tone-in-noise (TIN) detection in budgerigars (Melopsittacus undulatus, either sex), a parakeet species with human-like behavioral sensitivity to many simple and complex sounds. Behavioral sensitivity to tones in band-limited noise was assessed using operant-conditioning procedures. Neural recordings were made in awake animals from midbrain-level neurons in the inferior colliculus, the first processing stage of the ascending auditory pathway with pronounced rate-based encoding of stimulus amplitude modulation. Budgerigar TIN detection thresholds were similar to human thresholds across the full range of frequencies (0.5-4 kHz) and noise levels (45-85 dB SPL) tested. Also as in humans, thresholds were minimally affected by a challenging roving-level condition with random variation in background-noise level. Many midbrain neurons showed a decreasing response rate as TIN signal-to-noise ratio (SNR) was increased by elevating the tone level, a pattern attributable to amplitude-modulation tuning in these cells and the fact that higher SNR tone-plus-noise stimuli have flatter amplitude envelopes. TIN thresholds of individual neurons were as sensitive as behavioral thresholds under most conditions, perhaps surprisingly even when the unit's characteristic frequency was tuned an octave or more away from the test frequency. A model that combined responses of two cell types enhanced TIN sensitivity in the roving-level condition. These results highlight the importance of midbrain-level envelope encoding and off-frequency neural channels for hearing in noise.SIGNIFICANCE STATEMENT Detection of target sounds in noise is often assumed to depend on energy-level encoding by neural processing channels tuned to the target frequency. In contrast, we found that tone-in-noise sensitivity in budgerigars was often greatest in midbrain neurons not tuned to the test frequency, underscoring the potential importance of off-frequency channels for perception. Furthermore, the results highlight the importance of envelope processing for hearing in noise, especially under challenging conditions with random variation in background noise level over time.

Effects of Kainic Acid-Induced Auditory Nerve Damage on Envelope-Following Responses in the Budgerigar (Melopsittacus undulatus).

Sensorineural hearing loss is a prevalent problem that adversely impacts quality of life by compromising interpersonal communication. While hair cell damage is readily detectable with the clinical audiogram, this traditional diagnostic tool appears inadequate to detect lost afferent connections between inner hair cells and auditory nerve (AN) fibers, known as cochlear synaptopathy. The envelope-following response (EFR) is a scalp-recorded response to amplitude modulation, a critical acoustic feature of speech. Because EFRs can have greater amplitude than wave I of the auditory brainstem response (ABR; i.e., the AN-generated component) in humans, the EFR may provide a more sensitive way to detect cochlear synaptopathy. We explored the effects of kainate- (kainic acid) induced excitotoxic AN injury on EFRs and ABRs in the budgerigar (Melopsittacus undulatus), a parakeet species used in studies of complex sound discrimination. Kainate reduced ABR wave I by 65-75 % across animals while leaving otoacoustic emissions unaffected or mildly enhanced, consistent with substantial and selective AN synaptic loss. Compared to wave I loss, EFRs showed similar or greater percent reduction following kainate for amplitude-modulation frequencies from 380 to 940 Hz and slightly less reduction from 80 to 120 Hz. In contrast, forebrain-generated middle latency responses showed no consistent change post-kainate, potentially due to elevated "central gain" in the time period following AN damage. EFR reduction in all modulation frequency ranges was highly correlated with wave I reduction, though within-animal effect sizes were greater for higher modulation frequencies. These results suggest that even low-frequency EFRs generated primarily by central auditory nuclei might provide a useful noninvasive tool for detecting synaptic injury clinically.

Effects of selective auditory-nerve damage on the behavioral audiogram and temporal integration in the budgerigar.

Auditory-nerve fibers are lost steadily with age and as a possible consequence of noise-induced glutamate excitotoxicity. Auditory-nerve loss in the absence of other cochlear pathologies is thought to be undetectable with a pure-tone audiogram while degrading real-world speech perception (hidden hearing loss). Perceptual deficits remain unclear, however, due in part to the limited behavioral capacity of existing rodent models to discriminate complex sounds. The budgerigar is an avian vocal learner with human-like behavioral sensitivity to many simple and complex sounds and the capacity to mimic speech. Previous studies in this species show that intracochlear kainic-acid infusion reduces wave 1 of the auditory brainstem response by 40-70%, consistent with substantial excitotoxic auditory-nerve damage. The present study used operant-conditioning procedures in trained budgerigars to quantify kainic-acid effects on tone detection across frequency (0.25-8 kHz; the audiogram) and as a function of duration (20-160 ms; temporal integration). Tone thresholds in control animals were lowest from 1 to 4 kHz and decreased with increasing duration as in previous studies of the budgerigar. Behavioral results in kainic-acid-exposed animals were as sensitive as in controls, suggesting preservation of the audiogram and temporal integration despite auditory-nerve loss associated with up to 70% wave 1 reduction. Distortion-product otoacoustic emissions were also preserved in kainic-acid exposed animals, consistent with normal hair-cell function. These results highlight considerable perceptual resistance of tone-detection performance with selective auditory-nerve loss. Future behavioral studies in budgerigars with auditory-nerve damage can use complex speech-like stimuli to help clarify aspects of auditory perception impacted by this common cochlear pathology.

Formant-frequency discrimination of synthesized vowels in budgerigars (Melopsittacus undulatus) and humans.

Vowels are complex sounds with four to five spectral peaks known as formants. The frequencies of the two lowest formants, F1and F2, are sufficient for vowel discrimination. Behavioral studies show that many birds and mammals can discriminate vowels. However, few studies have quantified thresholds for formant-frequency discrimination. The present study examined formant-frequency discrimination in budgerigars (Melopsittacus undulatus) and humans using stimuli with one or two formants and a constant fundamental frequency of 200 Hz. Stimuli had spectral envelopes similar to natural speech and were presented with random level variation. Thresholds were estimated for frequency discrimination of F1, F2, and simultaneous F1 and F2 changes. The same two-down, one-up tracking procedure and single-interval, two-alternative task were used for both species. Formant-frequency discrimination thresholds were as sensitive in budgerigars as in humans and followed the same patterns across all conditions. Thresholds expressed as percent frequency difference were higher for F1 than for F2, and were unchanged between stimuli with one or two formants. Thresholds for simultaneous F1 and F2 changes indicated that discrimination was based on combined information from both formant regions. Results were consistent with previous human studies and show that budgerigars provide an exceptionally sensitive animal model of vowel feature discrimination.

Cues for auditory stream segregation of birdsong in budgerigars and zebra finches: Effects of location, timing, amplitude, and frequency.

Deciphering the auditory scene is a problem faced by many organisms. However, when faced with numerous overlapping sounds from multiple locations, listeners are still able to attribute the individual sound objects to their individual sound-producing sources. Here, the characteristics of sounds important for integrating versus segregating in birds were determined. Budgerigars and zebra finches were trained using operant conditioning procedures on an identification task to peck one key when they heard a whole zebra finch song and to peck another when they heard a zebra finch song missing a middle syllable. Once the birds were trained to a criterion performance level on those stimuli, probe trials were introduced on a small proportion of trials. The probe songs contained modifications of the incomplete training song's missing syllable. When the bird responded as if the probe was a whole song, it suggests they streamed together the altered syllable and the rest of the song. When the bird responded as if the probe was a non-whole song, it suggests they segregated the altered probe from the rest of the song. Results show that some features, such as location and intensity, are more important for segregating than other features, such as timing and frequency.

Multidrug therapy of Mycobacterium avium subsp. avium infection in experimentally inoculated budgerigars (Melopsittacus undulatus).

The aim of the study was to determine whether the four-month experimental therapy of mycobacteriosis in budgerigars may cause a complete recovery. A group of nine budgerigars was infected with a Mycobacterium avium subsp. avium isolate with proven pathogenicity for budgerigars. Five weeks post-inoculation, multidrug therapy was started. Another group comprising six birds received the same treatment but no infection, and the third group also comprising six birds was kept without infection or treatment as a control. The adopted antibiotic regimen included clarithromycin 61 mg/kg b.w., moxifloxacin 25 mg/kg b.w. and ethambutol 60 mg/kg b.w. administered by crop gavage every 12 h for 18 weeks. Despite a significant improvement in the condition of the infected, treated birds, the four-month therapy was not sufficient for the complete recovery of all.

Temporal coherence for complex signals in budgerigars (Melopsittacus undulatus) and humans (Homo sapiens).

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 behavioral results investigating temporal coherence, the results from this experiment illustrate that temporal cues are particularly important for auditory scene analysis across multiple species and for both simple and complex acoustic signals.

An outbreak of thyroid hyperplasia (goiter) with high mortality in budgerigars (Melopsittacus undulatus).

An outbreak of goiter with high morbidity and mortality in a flock of budgerigars (Melopsittacus undulatus) in California is described. Forty-five out of 400 adult birds exhibited signs of illness, weight loss, and enlargement in the crop area; 15 of the 45 birds died over a 2-3-month period. Diet consisted of a commercial mixture with the addition of broccoli, whole oats, and carrots, but no minerals or supplements. Six budgerigars were subjected to necropsy; all 6 birds had severely enlarged thyroid glands. Thyroid follicular hyperplasia was histologically observed in all birds examined, while granulomatous thyroiditis and microfollicular adenoma were observed in 2 birds, respectively. Virological, bacteriological, parasitological, and heavy metal analyses were negative or within normal limits. The total iodine in the thyroid glands of affected birds was measured by inductively coupled plasma-mass spectrometry. Following iodine supplementation and removal of broccoli from the diet, the owner reported weight gain and a reduced death rate among clinically affected birds; no additional birds became sick. The presence of broccoli with its iodine-binding ability and the complete lack of added minerals in the diet of these animals were thought to be the predisposing factors for the outbreak in the present study. Outbreaks of goiter accompanied by high mortality are rare in any species and, to the best of the authors' knowledge, have not been described previously in any avian species. Recognition of this condition may help improve medical, welfare, and trade standards concerning this species.

Determination of a safe and effective ultraviolet B radiant dose in budgerigars (Melopsittacus undulatus): a pilot study.

The object of this study was to establish a minimum dose of ultraviolet B (UVB) radiation capable of producing an erythemal reaction in budgerigars (Melopsittacus undulatus), to determine a threshold dose of UVB for vitamin D photoconversion, and to investigate the use of safer UVB wavelengths. In each of 5 experiments of this study, 20 birds were divided into a control group (n = 10) and a UVB irradiated group (n = 10). Light sources that provide broadband UVB wavelengths (280-315 nm) and narrowband UVB (310-320 nm) were used. Varied doses of UVB radiation were administered to budgerigars by altering exposure time and irradiance. Safety was determined by observing body weight and incidence of photokeratitis and photodermatitis. Efficacy was evaluated by measuring changes in serum 25-hydroxycholecalciferol levels. Serum corticosterone was measured in 1 experiment to monitor stress levels. The results demonstrated that exposure to 180 mJ/cm2 broadband UVB induced vitamin D photoconversion, decreased body weights, and increased serum corticosterone levels. At these wavelengths, UVB-induced lesions were observed. A broadband UVB of 150 to 300 mJ/cm2 was determined as the minimum erythema dose, and the threshold dose for vitamin D photoconversion was calculated to be in the range of 113-225 mJ/cm2. No erythemal lesions or vitamin D photoconversion took place after exposure to up to 1730 mJ/cm2 narrowband UVB radiation. A minimum erythema dose and a threshold dose for vitamin D conversion need to be determined for each species if phototherapy is to be considered as a safe and effective therapeutic or husbandry tool.

Lateralization of acoustic signals by dichotically listening budgerigars (Melopsittacus undulatus).

Sound localization allows humans and animals to determine the direction of objects to seek or avoid and indicates the appropriate position to direct visual attention. Interaural time differences (ITDs) and interaural level differences (ILDs) are two primary cues that humans use to localize or lateralize sound sources. There is limited information about behavioral cue sensitivity in animals, especially animals with poor sound localization acuity and small heads, like budgerigars. ITD and ILD thresholds were measured behaviorally in dichotically listening budgerigars equipped with headphones in an identification task. Budgerigars were less sensitive than humans and cats, and more similar to rabbits, barn owls, and monkeys, in their abilities to lateralize dichotic signals. Threshold ITDs were relatively constant for pure tones below 4 kHz, and were immeasurable at higher frequencies. Threshold ILDs were relatively constant over a wide range of frequencies, similar to humans. Thresholds in both experiments were best for broadband noise stimuli. These lateralization results are generally consistent with the free field localization abilities of these birds, and add support to the idea that budgerigars may be able to enhance their cues to directional hearing (e.g., via connected interaural pathways) beyond what would be expected based on head size.

Masked auditory thresholds in three species of birds, as measured by the auditory brainstem response (L).

Auditory brainstem responses (ABRs) were recorded in adult budgerigars, canaries, and zebra finches in quiet and in three levels of white noise for tone stimuli between 1 and 4 kHz. Similar to behavioral results, masked ABR thresholds increased linearly with increasing noise levels. When the three species are considered together, ABR-derived CRs were higher than behavioral CRs by 18-23 dB between 2 and 4 kHz and by about 30 dB at 1 kHz. This study clarifies the utility of using ABRs for estimating masked auditory thresholds in natural environmental noises in species that cannot be tested behaviorally.

The dusp1 immediate early gene is regulated by natural stimuli predominantly in sensory input neurons.

Many immediate early genes (IEGs) have activity-dependent induction in a subset of brain subdivisions or neuron types. However, none have been reported yet with regulation specific to thalamic-recipient sensory neurons of the telencephalon or in the thalamic sensory input neurons themselves. Here, we report the first such gene, dual specificity phosphatase 1 (dusp1). Dusp1 is an inactivator of mitogen-activated protein kinase (MAPK), and MAPK activates expression of egr1, one of the most commonly studied IEGs, as determined in cultured cells. We found that in the brain of naturally behaving songbirds and other avian species, hearing song, seeing visual stimuli, or performing motor behavior caused high dusp1 upregulation, respectively, in auditory, visual, and somatosensory input cell populations of the thalamus and thalamic-recipient sensory neurons of the telencephalic pallium, whereas high egr1 upregulation occurred only in subsequently connected secondary and tertiary sensory neuronal populations of these same pathways. Motor behavior did not induce high levels of dusp1 expression in the motor-associated areas adjacent to song nuclei, where egr1 is upregulated in response to movement. Our analysis of dusp1 expression in mouse brain suggests similar regulation in the sensory input neurons of the thalamus and thalamic-recipient layer IV and VI neurons of the cortex. These findings suggest that dusp1 has specialized regulation to sensory input neurons of the thalamus and telencephalon; they further suggest that this regulation may serve to attenuate stimulus-induced expression of egr1 and other IEGs, leading to unique molecular properties of forebrain sensory input neurons.

Impacts of dietary antioxidants and flight training on post-exercise oxidative damage in adult parrots.

After intense physical activity animals generally experience a rise in metabolic rate, which is associated with a proliferation of pro-oxidants. If unchecked, these pro-oxidants can cause damage to DNA and peroxidation of lipids in cell walls. Two factors are thought to ameliorate post-exercise oxidative damage, at least in mammals: dietary antioxidants and exercise training. So far it is unknown whether birds benefit similarly from exercise training, although a positive effect of dietary antioxidants on take-off flight has been indicated. In this experiment, we maintained captive wildtype budgerigars Melopsittacus undulatus on enhanced (EQ) or reduced quality (RQ) diets differing in levels of the dietary antioxidants retinol, vitamin C and alpha-tocopherol for 12 months. Birds were then regularly trained to perform take-off escape flights, a strenuous and biologically relevant form of exercise. For these adult budgerigars, regular exercise training improved escape flight performance, particularly in males on the EQ diet. In terms of oxidative damage, post-exercise levels of malondialdehyde (MDA), a by-product of lipid peroxidation, were significantly decreased after 9 weeks of flight training than after a single exercise session. Thus, individuals achieved faster escape flights with lower oxidative damage, after training. Also, birds that were fatter for their skeletal size initially had higher post-exercise MDA levels than thinner birds, but this relationship was broken by 9 weeks of flight training. Interestingly, there was no impact of diet quality on levels of MDA, suggesting that improved protection against oxidative damage for all birds was due to an up-regulation of endogenous antioxidant systems. Given their diversity, bird species provide rich research opportunities for investigating the interactions between exercise training, pro-oxidants production and antioxidant defences.

Comparison of treatment protocols for removing metallic foreign objects from the ventriculus of budgerigars (Melopsittacus undulatus).

To compare the efficacy of treatment protocols recommended to aid passage of metallic foreign objects from the ventriculus of birds, a 1-mm metal sphere, made from solder wire, was placed into the crop of each of 44 budgerigars (Melopsittacus undulatus). After survey radiographs confirmed the spheres were lodged in the ventriculus, birds were divided into 6 groups. Each group received 1 of 6 different treatment protocols: psyllium with grit, acidic drinking water, fine grit, coarse grit, cathartic emollients (peanut butter and mineral oil), and a control group. All birds were treated simultaneously with a chelating agent, dimercaptosuccinic acid (DMSA), to prevent heavy-metal toxicosis. Successive survey radiographs were used to monitor elimination of the spheres from the digestive tract. Of all protocols tested, birds treated with either fine or large grit had the shortest mean elimination time of the metal spheres. These results indicate that administration of grit particles, either fine or coarse, appears to be effective in hastening the passage of metallic foreign objects from the ventriculus of budgerigars.

Effects of syllable-final segment duration on the identification of synthetic speech continua by birds and humans.

In an attempt to test whether experience with or knowledge of language is necessary to show typical speaking rate effects in the perception of speech, budgerigars (Melopsittacus undulatus) and humans categorized stimuli from the synthetic continua /ba/-/wa/ and /bas/-/was/, with both short and long syllable-final phonemes. This comparative approach aims to shed some light on whether knowledge of language has a role in rate normalization effects, such as using duration information as an indicator of speaking rate in human speech perception. Syllable-final phoneme durations were varied, and were either temporally adjacent to the initial target (CV series) or were nonadjacent (CVC series). The birds were always influenced by syllable-final duration variation in the present experiments and displayed greater boundary shifts than humans. In humans, there was a significant boundary shift observed in the CV series, but there were no effects of duration variation in the final segment in the CVC series. The results from the birds suggest that specialized speech-based principles may not be necessary for explaining findings of grouping speech or speechlike elements in perception.

Discrimination of auditory gratings in birds.

Auditory gratings (also called auditory ripples) are a family of complex, broadband sounds with sinusoidally modulated logarithmic amplitudes and a drifting spectral envelope. These stimuli have been studied both physiologically in mammals and psychophysically in humans. Auditory gratings share spectro-temporal properties with many natural sounds, including species-specific vocalizations and the formant transitions of human speech. We successfully trained zebra finches and budgerigars, using operant conditioning methods, to discriminate between flat-spectrum broadband noise and noises with ripple spectra of different densities that moved up or down in frequency at various rates. Results show that discrimination thresholds (minimum modulation depth) increased as a function of increasing grating periodicity and density across all species. Results also show that discrimination in the two species of birds was better at those grating periodicities and densities that are prominent in their species-specific vocalizations. Budgerigars were generally more sensitive than both zebra finches and humans. Both bird species showed greater sensitivity to descending auditory gratings, which mirrors the main direction in their vocalizations. Humans, on the other hand, showed no directional preference even though speech is somewhat downward directional. Overall, our results are suggestive of both common strategies in the processing of complex sounds between birds and mammals and specialized, species-specific variations on that processing in birds.

The effects of short-term antioxidant supplementation on oxidative stress and flight performance in adult budgerigars Melopsittacus undulatus.

Antioxidants are known to play an important role in quenching reactive oxygen species (ROS), thus ameliorating oxidative stress. Since increased metabolism associated with exercise can increase oxidative stress, dietary antioxidants may be a limiting factor in determining aspects of physical performance. Here we tested whether oxidative stress associated with flight exercise of captive adult budgerigars, Melopsittacus undulatus differed after they received a diet containing either enhanced (EQ) or reduced levels (RQ) of a nutritional supplement (Nutrivit) rich in antioxidants for 4 weeks. We also assessed differences in take-off escape time, a potential fitness-determining physiological capability. Oxidative stress was measured in two ways: comet assay to measure DNA damage; and analysis of malondialdehyde (MDA), a by-product of lipid peroxidation. Flight exercise appeared to increase oxidative stress. Moreover, birds had a higher percentage of intact DNA (fewer alkali labile sites) in one comet measure and lower levels of MDA after an EQ diet than after an RQ diet. We found no difference in flight performance between the two diets. Our results suggested that birds exerted maximum effort in escape flights, regardless of diet. However, this was at a cost of increased oxidative stress post-flight when on a reduced quality diet, but not when on an enhanced, antioxidant-rich diet. We suggest that dietary antioxidants may prove important in reducing exercise-related costs through multiple physiological pathways. Further work is necessary to fully understand the effects of antioxidants and oxidative stress on exercise performance in the longer term.

Effects of two diets on the haematology, plasma chemistry and intestinal flora of budgerigars (Melopsittacus undulatus).

Two groups of 22 budgerigars (Melopsittacus undulatus) were housed for 12 months under identical conditions. One group was fed a commercial seed mixture plus carrots and a mineral supplement, and the other group was fed a commercially formulated diet plus carrots. Samples of blood and faeces were collected initially and after three, six, nine and 12 months. There were no significant differences between the haematological values of the two groups. The group fed the seed mixture had significantly higher concentrations of glucose, albumin, triglycerides and uric acid, and higher activity of aspartate aminotransferase, but the values were within the published reference ranges for normal birds. There were no significant differences between the faecal samples from the two groups, except that the fungus Macrorhabdus ornithogaster was identified in 48.3 per cent of the samples from the group fed the commercially formulated diet but from only 3.4 per cent of the samples from the group fed the seed mixture.