Single Sound Pulses Research Articles

Lesions of abdominal connectives reveal a conserved organization of the calling song central pattern generator (CPG) network in different cricket species

Although crickets move their front wings for sound production, the abdominal ganglia house the network of the singing central pattern generator. We compared the effects of specific lesions to the connectives of the abdominal ganglion chain on calling song activity in four different species of crickets, generating very different pulse patterns in their calling songs. In all species, singing activity was abolished after the connectives between the metathoracic ganglion complex and the first abdominal ganglion A3 were severed. The song structure was lost and males generated only single sound pulses when connectives between A3 and A4 were cut. Severing connectives between A4 and A5 had no effect in the trilling species, it led to an extension of chirps in a chirping species and to a loss of the phrase structure in two Teleogryllus species. Cutting the connectives between A5 and A6 caused no or minor changes in singing activity. In spite of the species-specific pulse patterns of calling songs, our data indicate a conserved organisation of the calling song motor pattern generating network. The generation of pulses is controlled by ganglia A3 and A4 while A4 and A5 provide the timing information for the chirp and/or phrase structure of the song.

The influence of bat echolocation call duration and timing on auditory encoding of predator distance in noctuoid moths

Animals co-occur with multiple predators, making sensory systems that can encode information about diverse predators advantageous. Moths in the families Noctuidae and Erebidae have ears with two auditory receptor cells (A1 and A2) used to detect the echolocation calls of predatory bats. Bat communities contain species that vary in echolocation call duration, and the dynamic range of A1 is limited by the duration of sound, suggesting that A1 provides less information about bats with shorter echolocation calls. To test this hypothesis, we obtained intensity-response functions for both receptor cells across many moth species for sound pulse durations representing the range of echolocation call durations produced by bat species in northeastern North America. We found that the threshold and dynamic range of both cells varied with sound pulse duration. The number of A1 action potentials per sound pulse increases linearly with increasing amplitude for long-duration pulses, saturating near the A2 threshold. For short sound pulses, however, A1 saturates with only a few action potentials per pulse at amplitudes far lower than the A2 threshold for both single sound pulses and pulse sequences typical of searching or approaching bats. Neural adaptation was only evident in response to approaching bat sequences at high amplitudes, not search-phase sequences. These results show that, for short echolocation calls, a large range of sound levels cannot be coded by moth auditory receptor activity, resulting in no information about the distance of a bat, although differences in activity between ears might provide information about direction.

Pulse sound generation, anterior swim bladder buckling and associated muscle activity in the pyramid butterflyfish, Hemitaurichthys polylepis

Acoustic behaviors are widespread among diverse fish taxa but mechanisms of sound production are known from relatively few species, vary widely and convergent mechanisms are poorly known. We examined the sound production mechanism in the pyramid butterflyfish, Hemitaurichthys polylepis, a member of the socially and ecologically diverse reef fish family Chaetodontidae. In the field, fish produce pulse trains at dusk during social interactions that are probably related to mate attraction and courtship. In laboratory experiments, sound production was synchronized to high-speed video to determine body movement associated with sound generation. In addition, electromyography (EMG) recordings tested the activity of six candidate muscles. Fish produced individual pulses with a mean peak frequency of 97 Hz in rapid succession. EMG experiments show that anterior hypaxial muscles contract at high bilaterally synchronous rates (up to 120 Hz) in near perfect association with rapid inward buckling visible outside the body over the anterior swim bladder. Muscle activity often showed EMG doublets that occurred within the time of a single sound pulse but was not sustained. Buckling and sound pulse rates correlated strongly (R(2)≈1.00) and sound pulse rate measured over two successive pulses (maximum of 38 pulses s(-1)) was lower than muscle firing rate. These results show that the extrinsic swim bladder muscles of pyramid butterflyfish involve single contractions that produce pulses in a manner similar to distantly related teleosts, but involve a novel doublet motor-neuron firing pattern. Thus, the sound production mechanism in pyramid butterflyfish is likely convergent with several percomorph taxa and divergent from the related chaetodontid genus Forcipiger.

BOLD correlates of edge detection in human auditory cortex

Edges are important cues defining coherent auditory objects. As a model of auditory edges, sound on- and offset are particularly suitable to study their neural underpinnings because they contrast a specific physical input against no physical input. Change from silence to sound, that is onset, has extensively been studied and elicits transient neural responses bilaterally in auditory cortex. However, neural activity associated with sound onset is not only related to edge detection but also to novel afferent inputs. Edges at the change from sound to silence, that is offset, are not confounded by novel physical input and thus allow to examine neural activity associated with sound edges per se. In the first experiment, we used silent acquisition functional magnetic resonance imaging and found that the offset of pulsed sound activates planum temporale, superior temporal sulcus and planum polare of the right hemisphere. In the planum temporale and the superior temporal sulcus, offset response amplitudes were related to the pulse repetition rate of the preceding stimulation. In the second experiment, we found that these offset-responsive regions were also activated by single sound pulses, onset of sound pulse sequences and single sound pulse omissions within sound pulse sequences. However, they were not active during sustained sound presentation. Thus, our data show that circumscribed areas in right temporal cortex are specifically involved in identifying auditory edges. This operation is crucial for translating acoustic signal time series into coherent auditory objects.

Neurite‐specific Ca2+ dynamics underlying sound processing in an auditory interneurone

Concepts on neuronal signal processing and integration at a cellular and subcellular level are driven by recording techniques and model systems available. The cricket CNS with the omega-1-neurone (ON1) provides a model system for auditory pattern recognition and directional processing. Exploiting ON1's planar structure we simultaneously imaged free intracellular Ca(2+) at both input and output neurites and recorded the membrane potential in vivo during acoustic stimulation. In response to a single sound pulse the rate of Ca(2+) rise followed the onset spike rate of ON1, while the final Ca(2+) level depended on the mean spike rate. Ca(2+) rapidly increased in both dendritic and axonal arborizations and only gradually in the axon and the cell body. Ca(2+) levels were particularly high at the spike-generating zone. Through the activation of a Ca(2+)-sensitive K(+) current this may exhibit a specific control over the cell's electrical response properties. In all cellular compartments presentation of species-specific calling song caused distinct oscillations of the Ca(2+) level in the chirp rhythm, but not the faster syllable rhythm. The Ca(2+)-mediated hyperpolarization of ON1 suppressed background spike activity between chirps, acting as a noise filter. During directional auditory processing, the functional interaction of Ca(2+)-mediated inhibition and contralateral synaptic inhibition was demonstrated. Upon stimulation with different sound frequencies, the dendrites, but not the axonal arborizations, demonstrated a tonotopic response profile. This mirrored the dominance of the species-specific carrier frequency and resulted in spatial filtering of high frequency auditory inputs.

Pulses, patterns and paths: neurobiology of acoustic behaviour in crickets

Crickets use acoustic communication for pair formation. Males sing with rhythmical movements of their wings and the mute females approach the singing males by phonotaxis. Females walking on a trackball rapidly steer towards single sound pulses when exposed to split-song paradigms. Their walking path emerges from consecutive reactive steering responses, which show no temporal selectivity. Temporal pattern recognition is tuned to the species-specific syllable rate and gradually changes the gain of auditory steering. If pattern recognition is based on instantaneous discharge rate coding, then the tuning to the species-specific song pattern may already be present at the level of thoracic interneurons. During the processing of song patterns, changes in cytosolic Ca(2+ )concentrations occur in phase with the chirp rhythm in the local auditory interneurone. Male singing behaviour is controlled by command neurons descending from the brain. The neuropil controlling singing behaviour is located in the anterior protocerebrum next to the mushroom bodies. Singing behaviour is released by injection of cholinergic agonists and inhibited by gamma-butyric acid (GABA). During singing, the sensitivity of the peripheral auditory system remains unchanged but a corollary discharge inhibits auditory processing in afferents and interneurons within the prothoracic auditory neuropil and prevents the auditory neurons from desensitisation.

Mechanisms underlying phonotactic steering in the cricketGryllus bimaculatusrevealed with a fast trackball system

Phonotactic steering behaviour of the cricket G. bimaculatus was analysed with a new highly sensitive trackball system providing a spatial and temporal resolution of 127 microm and 0.3 ms, respectively. Orientation to artificial calling songs started at 45 dB SPL, it increased up to 75 dB SPL and then saturated. When exposed to two identical patterns of different intensity, crickets significantly steered towards the louder sound pattern, whenever the intensity difference was greater than 1 dB. Bilateral latency differences in sound presentation did not always cause clear orientation towards the leading side. The overall walking direction depended on the number of sound pulses perceived from the left or right side with the animals turning towards the side providing the larger number of pulses. The recordings demonstrated rapid changes in walking direction performed even during a chirp. These rapid steering responses occurred with a latency of 55-60 ms, well before the central nervous system had time to evaluate the temporal structure of a whole chirp. When every other sound pulse was presented from opposite directions, the crickets followed the temporal pattern of sound presentation and rapidly steered towards the left and right side. Steering towards individual sound pulses does not agree with the proposal that crickets analyse the quality of sound patterns and then steer towards the better pattern. Rather, these experiments suggest that fast steering to single sound pulses determines the lateral deviation of the animals and that complex auditory orientation emerges from this simple mechanism of auditory steering.

Effects of fish size and temperature on weakfish disturbance calls: implications for the mechanism of sound generation.

To categorize variation in disturbance calls of the weakfish Cynoscion regalis and to understand their generation, we recorded sounds produced by different-sized fish, and by similar-sized fish at different temperatures, as well as muscle electromyograms. Single, simultaneous twitches of the bilateral sonic muscles produce a single sound pulse consisting of a two- to three-cycle acoustic waveform. Typical disturbance calls at 18 degrees C consist of trains of 2-15 pulses with a sound pressure level (SPL) of 74 dB re 20 microPa at 10 cm, a peak frequency of 540 Hz, a repetition rate of 20 Hz and a pulse duration of 3.5 ms. The pulse duration suggests an incredibly short twitch time. Sound pressure level (SPL) and pulse duration increase and dominant frequency decreases in larger fish, whereas SPL, repetition rate and dominant frequency increase and pulse duration decreases with increasing temperature. The dominant frequency is inversely related to pulse duration and appears to be determined by the duration of muscle contraction. We suggest that the lower dominant frequency of larger fish is caused by a longer pulse (=longer muscle twitch) and not by the lower resonant frequency of a larger swimbladder.

Secondary courtship songs and inhibitory songs ofDrosophila virilis-group males

The males of all Drosophila virilis-group species produce primary courtship song; and the males of four of these species also provide secondary courtship song when courting a female. The amount of secondary song and the courtship phase at which it is produced vary according to the species. D. lummei males produce secondary song consisting of successive 12-ms-long sound pulses with 70-ms-long intervals between pulses. D. borealis males produce short and dense pulse trains and D. littoralis and D. flavomontana males produce single sound pulses of a long duration (80-160 ms). The males of all species produce pulse-structured inhibitory song when they are courted by another male. In the secondary and inhibitory songs of interspecific hybrids, short and dense pulse trains of parent species break into pulse song with long interpulse intervals. This suggests that songs consisting of short and dense pulse trains and pulse songs with long interpulse intervals are just different modes of the same song. Sine songs (long sound pulses) seem to be inherited independently of pulse song.

Dissipation of Energy in an N-Shape Formation Process for Single Sinusoidal Sound Wave

Energy dissipation of N wave compared with linear attenuation in a circular pipe is discussed. A single sound pulse of finite amplitude which is initially sinusoidal propagates into the pipe and its wave form is distorted by the nonlinear effects in addition to the linear absorption caused by the tube-wall effects. It is found in some cases that the total dissipation of energy included in whole wave shows lower attenuation than that of the small amplitude wave, despite its nonlinear distortion effect. It is concluded that this propagation behaviour appears for the waveform progressively distorted from a sinusoidal to an N wave, because the attenuation of energy is unaffected by the nonlinear dissipation before a shock front is formed.

Insulation Characteristics of a Circular Plate for a Single Sound Pulse

Insulation Characteristics of a Circular Plate for a Single Sound Pulse