Hearing in the swamp sparrow,Melospiza georgiana,and the song sparrow,Melospiza melodia

Operant conditioning techniques and a psychophysical tracking procedure were used to measure thresholds for pure tones in two congeneric species of sparrows: swamp sparrows and song sparrows. Thresholds were measured both in quiet conditions and in the presence of white noise. The two species were similar in their gross pattern of auditory sensitivity with most sensitive thresholds in the frequency region of 1·0–8·0 kHz and poor hearing above and below this range. However, the best sensitivity occurred at 2 kHz for the song sparrows and at 4 kHz for the swamp sparrows. This pattern was also observed in song spectra of the two species. The songs of song sparrows had more power in lower frequencies than the songs of swamp sparrows. Masked auditory thresholds for both species were very similar, showing a generally increasing signal-to-noise ratio with increasing frequency. The similarity between swamp and song sparrows in these measures of basic auditory sensitivity suggests that the primary mechanisms underlying selective vocal learning in these sparrows probably reside at higher levels than the peripheral auditory sensitivities.     

A behavior analysis of absolute pitch: sex, experience, and species

Absolute pitch (AP) perception refers to the ability to identify, classify, and memorize pitches without use of an external reference pitch. In tests of AP, several species were trained to sort contiguous tones into three or eight frequency ranges, based on correlations between responding to tones in each frequency range and reinforcement. Two songbird species, zebra finches and white-throated sparrows, and a parrot species, budgerigars had highly accurate AP, they discriminated both three and eight ranges with precision. Relative to normally reared songbirds, isolate reared songbirds had impaired AP. Two mammalian species, humans and rats, had equivalent and weak AP, they discriminated three frequency ranges to a lackluster standard and they acquired only a crude discrimination of the lowest and highest of eight frequency ranges. In comparisons with mammals even isolate songbirds had more accurate AP than humans and rats.     

Encoding properties of auditory neurons in the brain of a soniferous damselfish: response to simple tones and complex conspecific signals

The fish auditory system encodes important acoustic stimuli used in social communication, but few studies have examined response properties of central auditory neurons to natural signals. We determined the features and responses of single hindbrain and midbrain auditory neurons to tone bursts and playbacks of conspecific sounds in the soniferous damselfish, Abudefduf abdominalis. Most auditory neurons were either silent or had slow irregular resting discharge rates <20 spikes s⁻¹. Average best frequency for neurons to tone stimuli was ~130 Hz but ranged from 80 to 400 Hz with strong phase-locking. This low-frequency sensitivity matches the frequency band of natural sounds. Auditory neurons were also modulated by playbacks of conspecific sounds with thresholds similar to 100 Hz tones, but these thresholds were lower than that of tones at other test frequencies. Thresholds of neurons to natural sounds were lower in the midbrain than the hindbrain. This is the first study to compare response properties of auditory neurons to both simple tones and complex stimuli in the brain of a recently derived soniferous perciform that lacks accessory auditory structures. These data demonstrate that the auditory fish brain is most sensitive to the frequency and temporal components of natural pulsed sounds that provide important signals for conspecific communication.     

Excitatory and inhibitory frequency zones of responses of posterior declivus cerebelli neurons

The impulse responses of 260 neurons of the posterior declivus cerebelli of anesthetized white rats to the effect of one or two tones of different frequencies were investigated. The principal characteristics of the frequency-threshold curves (FTC) were measured. It was shown that neurons of the posterior declivus cerebelli differ considerably in optimum frequency (f₀), thresholds to f₀, and sharpness of the FTC. The lateral inhibitory zones (LIZ) of the neurons investigated in response to the effect of two tones of different frequencies in 85% of the cases are located on both sides of the f₀ and partially overlap the FTC. A low-frequency LIZ is more effective in width of the inhibitory frequency band and a high frequency LIZ is more effective in level of intensity of the frequencies causing an inhibitory effect. The width of the frequency zone of the response narrows sharply in the case of the inhibitory interaction of two tones.Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 3, No. 4, pp. 369–378, July–August, 1971.     

Flying in tune: sexual recognition in mosquitoes

Mosquitoes hear with their antennae, which in most species are sexually dimorphic. Johnston, who discovered the mosquito auditory organ at the base of the antenna 150 years ago, speculated that audition was involved with mating behaviour. Indeed, male mosquitoes are attracted to female flight tones. The male auditory organ has been proposed to act as an acoustic filter for female flight tones, but female auditory behavior is unknown. We show, for the first time, interactive auditory behavior between males and females that leads to sexual recognition. Individual males and females both respond to pure tones by altering wing-beat frequency. Behavioral auditory tuning curves, based on minimum threshold sound levels that elicit a change in wing-beat frequency to pure tones, are sharper than the mechanical tuning of the antennae, with males being more sensitive than females. We flew opposite-sex pairs of tethered Toxorhynchites brevipalpis and found that each mosquito alters its wing-beat frequency in response to the flight tone of the other, so that within seconds their flight-tone frequencies are closely matched, if not completely synchronized. The flight tones of same-sex pairs may converge in frequency but eventually diverge dramatically.     

Why longer song elements are easier to detect: threshold level-duration functions in the Great Tit and comparison with human data

Our study estimates detection thresholds for tones of different durations and frequencies in Great Tits (Parus major) with operant procedures. We employ signals covering the duration and frequency range of communication signals of this species (40–1,010 ms; 2, 4, 6.3 kHz), and we measure threshold level-duration (TLD) function (relating threshold level to signal duration) in silence as well as under behaviorally relevant environmental noise conditions (urban noise, woodland noise). Detection thresholds decreased with increasing signal duration. Thresholds at any given duration were a function of signal frequency and were elevated in background noise, but the shape of Great Tit TLD functions was independent of signal frequency and background condition. To enable comparisons of our Great Tit data to those from other species, TLD functions were first fitted with a traditional leaky-integrator model. We then applied a probabilistic model to interpret the trade-off between signal amplitude and duration at threshold. Great Tit TLD functions exhibit features that are similar across species. The current results, however, cannot explain why Great Tits in noisy urban environments produce shorter song elements or faster songs than those in quieter woodland environments, as detection thresholds are lower for longer elements also under noisy conditions.     

External auditory structures in two species of neotropical notodontid moths

Summary Two species of neotropical moths,Antaea lichyi Franclemont andHapigia curvilinea Schaus (Notodontidae) from Panamá possess paired, cup-like extensions of their pleural segments, reminiscent of mammalian pinnae, that project laterally from the perimeter of the tympanic membrane. These cups are homologous with the post-spiracular abdominal hoods of typical noctuid moths, and may be related to the orientation of the notodontid ear, where the tympanic membrane faces ventrally toward the mid-line of the moth's body and potentially reduces the reception of incident sound energy.Removal of the cups did not alter the neurologically determined best frequencies of either species, nor did it affect the shape ofH. curvilinea's directional sensitivity or its spatial point of maximal sensitivity. Polar threshold curves to stimulus tones of 30 kHz, however, revealed a reduced overall directionality, and thus indicate that the cups may impart a degree of sound localization ability.Both removal and blockage of the external structures result in reduced sensitivities (i.e. increased thresholds) to frequencies higher than approximately 30 kHz. All individuals ofH. curvilinea tested became deaf to tones over 115 kHz when the cups were ablated or blocked.Neotropical moths are exposed to potentially heavy predation pressure from insectivorous bats that characteristically emit faint and/or high frequency echolocation signals, some in excess of 70 kHz (e.g., foliage-gleaning Phyllostomatidae). In certain notodontids, the development of external auditory adaptations that enhance the reception of faint, high frequency sounds may be an evolutionary response to predation pressures by these bats.     

Responses to pure tones and linear FM components of the CF — FM biosonar signal by single units in the inferior colliculus of the mustached bat

The responses of 682 single-units in the inferior colliculus (IC) of 13 mustached bats (Pteronotus parnellii parnellii) were measured using pure tones (CF), frequency modulations (FM) and pairs of CF-FM signals mimicking the species' biosonar signal, which are stimuli known to be essential to the responses of CF/CF and FM-FM facilitation neurons in auditory cortex. Units were arbitrarily classified into 'reference frequency' (RF), 'FM2' and 'Non-echolocation' (NE) categories according to the relationship of their best frequencies (BF) to the biosonar signal frequencies. RF units have high Q10dB values and are tuned to the reference frequency of each bat, which ranged between 60.73 and 62.73 kHz. FM2 units had BF's between 50 and 60 kHz, while NE units had BF's outside the ranges of the RF and FM2 classes. PST histograms of the responses revealed discharge patterns such as 'onset', 'onset-bursting' (most common), 'on-off', 'tonic-on','pauser', and 'chopper'. Changes in discharge patterns usually resulted from changes in the frequency and/or intensity of the stimuli, most often involving a change from onset-bursting to on-off. Different patterns were also elicited by CF and FM stimuli. Frequency characteristics and thresholds to CF and FM stimuli were measured. RF neurons were very sharply tuned with Q10dB's ranging from 50-360. Most (92%) also responded to FM2 stimuli, but 78% were significantly more sensitive (greater than 5 dB) to CF stimuli, and only 3% had significantly lower thresholds to FM2. The best initial frequency for FM2 sweeps in RF units was 65.35 +/- 2.138 kHz (n = 118), well above the natural frequency of the 2nd harmonic. FM2 and NE units were indistinguishable from each other, but were quite different from RF units: 41% of these two classes had lower thresholds to CF, 49% were about equally sensitive, and 10% had lower thresholds to FM. For FM2 units, mean best initial frequency for FM was 60.94 kHz +/- 3.162 kHz (n = 114), which is closely matched to the 2nd harmonic in the biosonar signal. Very few units (5) responded only to FM signals, i.e., were FM-specialized. The characteristics of spike-count functions were determined in 587 units. The vast majority (79%) of RF units (n = 228) were nonmonotonic, and about 22% had upper-thresholds.(ABSTRACT TRUNCATED AT 400 WORDS)     

Development of the visual preference of chimpanzees (<Emphasis Type="Italic">Pan troglodytes</Emphasis>) for photographs of primates: effect of social experience

In a study by Tanaka (2003) five captive chimpanzees preferred photographs of humans to those of chimpanzees. All the subjects were raised by humans and lived in captivity for many years. This suggests their preference might have developed through social experience. In this study examined this hypothesis by using three young chimpanzees raised by their mothers in a captive chimpanzee community. The young chimpanzees were tested four times before six years of age. I also tested eight adult chimpanzees that had been in captivity for more than 20 years. Each subject was presented with digitized color photographs of different species of primates on a touch-sensitive screen. The subjects received a food reward when they touched a photograph, irrespective of which photograph they touched. All the adult chimpanzees touched photographs of humans more frequently than those of any other species of primate. Two of the young chimpanzees showed no species preference before reaching 5 years of age, when they started to show preference for humans. The remaining young chimpanzee consistently preferred chimpanzees. These results suggest that development of visual preference of chimpanzees is affected by social experience during infancy.     

How chimpanzees look at pictures: a comparative eye-tracking study

Surprisingly little is known about the eye movements of chimpanzees, despite the potential contribution of such knowledge to comparative cognition studies. Here, we present the first examination of eye tracking in chimpanzees. We recorded the eye movements of chimpanzees as they viewed naturalistic pictures containing a full-body image of a chimpanzee, a human or another mammal; results were compared with those from humans. We found a striking similarity in viewing patterns between the two species. Both chimpanzees and humans looked at the animal figures for longer than at the background and at the face region for longer than at other parts of the body. The face region was detected at first sight by both species when they were shown pictures of chimpanzees and of humans. However, the eye movements of chimpanzees also exhibited distinct differences from those of humans; the former shifted the fixation location more quickly and more broadly than the latter. In addition, the average duration of fixation on the face region was shorter in chimpanzees than in humans. Overall, our results clearly demonstrate the eye-movement strategies common to the two primate species and also suggest several notable differences manifested during the observation of pictures of scenes and body forms.     

Comparison of the physiology of the auditory receptor organs in Gryllus bimaculatus and Ephippiger ephippiger: CSD Recordings within the auditory neuropiles

The syllables of the song of the tettigoniid Ephippiger ephippiger consist of a series of short sound impulses with a broad-banded frequency spectrum. Syllables of the song of the gryllid species Gryllus bimaculatus are nearly pure tones with sharply tuned frequency maxima. A comparison of the physiology of the audiotory receptor organs of both species was carried out by using acoustical stimuli with different carrier frequencies and time-amplitude patterns. The neuronal ensemble activity of receptor cell groups of the tympanal organ was measured within the prothoracic ganglion using the CSD technique. In E. ephippiger, response maxima were found at carrier frequencies mirroring the broad frequency content of the conspecific song. The receptor cells of E. ephippiger are highly sensitive to transient sound impulses. In G. bimaculatus, the receptor cell population is more sharply tuned to the basic frequencies of the natural songs; pure tones represent more effective stimuli than transient sound signals. The causes for these speciesspecific differences are discussed with regard to probable adaptations of the receptor organs to the parameters of the conspecific songs. © 1993 John Wiley & Sons, Inc.     

Gene diversity patterns at 10 X-chromosomal loci in humans and chimpanzees

We have investigated the pattern and extent of nucleotide diversityin 10 X-chromosomal genes where mutations are known to causemental retardation in humans. For each gene, we sequenced theentire coding region from cDNA in humans, chimpanzees, and orangutans,as well as about 3 kb of genomic DNA in 20 humans sampled worldwideand in 10 chimpanzees representing two "subspecies." Overallnucleotide diversity in these genes is about twofold lower inhumans than in chimpanzees, and nucleotide diversity withinand between species is low, suggesting that a high level offunctional constraint acts on these genes. Strikingly, we findthat a summary of the allele frequency spectrum is significantlycorrelated in humans and chimpanzees, perhaps reflecting verysimilar levels of constraint at these genes in the two species.A possible exception is FMR2, which shows a higher number ofnonsynonymous than synonymous substitutions on the human lineage,suggesting the action of positive selection.     

Discrimination of Low-Frequency Tones Employs Temporal Fine Structure

An auditory neuron can preserve the temporal fine structure of a low-frequency tone by phase-locking its response to the stimulus. Apart from sound localization, however, much about the role of this temporal information for signal processing in the brain remains unknown. Through psychoacoustic studies we provide direct evidence that humans employ temporal fine structure to discriminate between frequencies. To this end we construct tones that are based on a single frequency but in which, through the concatenation of wavelets, the phase changes randomly every few cycles. We then test the frequency discrimination of these phase-changing tones, of control tones without phase changes, and of short tones that consist of a single wavelet. For carrier frequencies below a few kilohertz we find that phase changes systematically worsen frequency discrimination. No such effect appears for higher carrier frequencies at which temporal information is not available in the central auditory system.     

Visual preference by chimpanzees (Pan troglodytes) for photos of primates measured by a free choice-order task: implication for influence of social experience

With a free-choice task, visual preference was estimated in five adult chimpanzees (Pan troglodytes). The subjects were presented with digitized color photographs of various species of primates on a CRT screen. Their touching responses to the photographs were reinforced by food reward irrespective of which photographs they touched. The results revealed that all chimpanzees touched the photographs of humans significantly more than any other species, or phylogenetic families of primates. This tendency was consistent across different stimulus sets. The results suggest that the chimpanzees showed visual preference for the photographs of humans over those of their own species. The results also suggest that the degree of this visual preference was not in accordance with phylogenetic distance from the subjects' species, chimpanzees. The preference for humans was stronger in the case of the colored photographs than in monochromatic ones. All of the five chimpanzees had been in captivity for at least 16 years. They were reared by humans from just after their birth, or at least from 1.5 years old. Their preference might have developed through social experience, especially that during infanthood. Electronic Publication     

A horse's eye view: size and shape discrimination compared with other mammals

Mammals have adapted to a variety of natural environments from underwater to aerial and these different adaptations have affected their specific perceptive and cognitive abilities. This study used a computer-controlled touchscreen system to examine the visual discrimination abilities of horses, particularly regarding size and shape, and compared the results with those from chimpanzee, human and dolphin studies. Horses were able to discriminate a difference of 14% in circle size but showed worse discrimination thresholds than chimpanzees and humans; these differences cannot be explained by visual acuity. Furthermore, the present findings indicate that all species use length cues rather than area cues to discriminate size. In terms of shape discrimination, horses exhibited perceptual similarities among shapes with curvatures, vertical/horizontal lines and diagonal lines, and the relative contributions of each feature to perceptual similarity in horses differed from those for chimpanzees, humans and dolphins. Horses pay more attention to local components than to global shapes.     

Differential sensitivity to conspecific and allospecific cues in chimpanzees and humans: a comparative eye-tracking study

Previous studies have shown that a variety of animals including humans are sensitive to social cues from others and shift their attention to the same objects attended to by others. However, little is known about how animals process conspecifics'' and another species'' actions, although primates recognize conspecific faces better than those of another species. In this study, using unrestrained eye-tracking techniques, we first demonstrated that conspecific social cues modulated looking behaviours of chimpanzees more than human cues, whereas human observers were equally sensitive to both species. Additionally, first pass gaze duration at the face indicates that chimpanzees looked at the chimpanzees'' face longer than the human face, suggesting that chimpanzees might extract more referential information from a conspecific face. These results also imply that a unique ability for extracting referential information from a variety of social objects has emerged during human evolution.     

Auditory frequency discrimination in the squirrel monkey

Four squirrel monkeys (Saimiri sciureus) were tested for their frequency discrimination capacity using an eyeblink classical conditioning procedure, with air puff against the eye as unconditioned stimulus and 600-ms pure tones as conditioned stimuli. Absolute frequency difference thresholds showed a minimum (20-41 Hz, mean 30 Hz) at 4,000-8,000 Hz and increased towards higher as well as lower frequencies (70-90 Hz, mean 80 Hz at 300 Hz; 44-120 Hz, mean 82 Hz at 16,000 Hz). Relative frequency difference thresholds increased from higher to lower frequencies, with values as low as 0.3-0.8% (mean 0.5%) at 16,000 Hz and as large as 24-30% (mean 27%) at 300 Hz. The squirrel monkey's frequency discrimination function thus shows a severe deviation from Weber's law. The frequency difference thresholds are comparable to human's in the 4,000-8,000 Hz range, but are 65-80 times higher in the 500- to 300-Hz range. Individuals with high auditory thresholds do not necessarily also have high frequency difference thresholds.     

P300 in young and elderly subjects: Auditory frequency and intensity effects

Auditory event-related potentials (ERPs) were assessed in young and elderly subjects when stimulus intensity (40 vs. 60 dB SL) and standard/target tone frequency (250/500 Hz and 1000/2000 Hz) were manipulated to study the effects of these variables on the P3(00) and N1, P2 and N2 components. Auditory thresholds for each stimulus type were obtained, and the stimulus intensity was adjusted to effect perceptually equal intensities across conditions for each subject. Younger subjects demonstrated larger P3 amplitudes and shorter latencies than elderly subjects. The low frequency stimuli produced larger P3 amplitude and shorter latencies than the high frequency stimuli. Low intensity stimuli yielded somewhat smaller P3 amplitudes and longer peak latencies than high intensity stimulus tones. Although additional stimulus intensity and frequency effects were obtained for the N1, P2 and N2 components, these generally differed relatively little with subject age. The findings suggest that auditory stimulus parameters contribute to P3 measures, which are different for young compared to elderly subjects.     

Spectral and temporal gating mechanisms enhance the clutter rejection in the echolocating bat,Rhinolophus rouxi

Summary Doppler shift compensation behaviour in horseshoe bats, Rhinolophus rouxi, was used to test the interference of pure tones and narrow band noise with compensation performance. The distortions in Doppler shift compensation to sinusoidally frequency shifted echoes (modulation frequency: 0.1 Hz, maximum frequency shift: 3 kHz) consisted of a reduced compensation amplitude and/or a shift of the emitted frequency to lower frequencies (Fig. 1).Pure tones at frequencies between 200 and 900 Hz above the bat's resting frequency (RF) disturbed the Doppler shift compensation, with a maximum of intererence between 400 and 550 Hz (Fig. 2). Minimum duration of pure tones for interference was 20 ms and durations above 40 ms were most effective (Fig. 3). Interfering pure tones arriving later than about 10 ms after the onset of the echolocation call showed markedly reduced interference (Fig. 4). Doppler shift compensation was affected by pure tones at the optimum interfering frequency with sound pressure levels down to –48 dB rel the intensity level of the emitted call (Figs. 5, 6).Narrow bandwidth noise (bandwidth from ± 100 Hz to ± 800 Hz) disturbed Doppler shift compensation at carrier frequencies between –250 Hz below and 800 Hz above RF with a maximum of interference between 250 and 500 Hz above resting frequency (Fig. 7). The duration and delay of the noise had similar influences on interference with Doppler shift compensation as did pure tones (Figs. 8, 9). Intensity dependence for noise interference was more variable than for pure tones (-32 dB to -45 dB rel emitted sound pressure level, Fig. 10).The temporal and spectral gating in Doppler shift compensation behaviour is discussed as an effective mechanism for clutter rejection by improving the processing of frequency and amplitude transients in the echoes of horseshoe bats.Abbreviations CF constant frequency - FM frequency modulation - RF resting frequency - SPL sound pressure level     

Auditory responses in the torus semicircularis of the cane toad, Bufo marinus. I. Field potential studies

Field potentials have been recorded in the torus semicircularis of the toad, Bufo marinus, in response to brief tones presented in the free field. The amplitude of the potentials varied with the frequency of the stimulus and location of the electrode along the rostro-caudal axis of the torus. All frequencies in the auditory range evoked largest potentials when the stimulus was located in the contralateral auditory field. Potentials evoked by low to mid frequencies were largest when the stimulus was located near the line orthogonal to the long axis of the animal. For progressively higher frequencies, the optimal stimulus position was progressively more anterior in the contralateral field. In animals in which one eighth nerve had been sectioned, field potentials evoked by tones of low to mid frequency were less sensitive to changes in stimulus direction than in normal animals. However, the directional sensitivity of field potentials evoked by mid to high frequencies was similar in monaural and normal animals. These observations suggest that binaural neural integration is important in determining the directional sensitivity of field potentials in the torus evoked by low to mid frequencies but not for potentials evoked by mid to high frequencies.