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Biomedical subjects

R A Suthers

Publications and source records attributed to R A Suthers.

17 recordsLinked to original sources
PubMed1996

Motor stereotypy and diversity in songs of mimic thrushes.

The relationship between the motor and acoustic similarity of song was examined in brown thrashers (Toxostoma rufum) and grey catbirds (Dumetella carolinensis) (family Mimidae), which have very large song repertoires and sometimes mimic other species. Motor similarity was assessed by cross correlation of syringeal airflows and air sac pressures that accompany sound production. Although most syllables were sung only once in the song analyzed, some were repeated, either immediately forming a couplet, or after a period of intervening song, as a distant repetition. Both couplets and distant repetitions are produced by distinctive, stereotyped motor patterns. Their motor similarity does not decrease as the time interval between repetitions increases, suggesting that repeated syllables are stored in memory as fixed motor programs. The acoustic similarity between nonrepeated syllables, as indicated by correlation of their spectrograms, has a significant positive correlation with their motor similarity. This correlation is weak, however, suggesting that there is no simple linear relationship between motor action and acoustic output and that similar sounds may sometimes be produced by different motor mechanisms. When compared without regard to the sequence in which they are sung, syllables paired for maximum spectral similarity form a continuum with repeated syllables in terms of their acoustic and motor similarity. The prominence of couplets in the "syntax" of normal song is enhanced by the dissimilarity of successive nonrepeated syllables that make up the remainder of the song.

Animals↗
PubMed1996

Role of syringeal muscles in gating airflow and sound production in singing brown thrashers.

1. The role of syringeal muscles in song production, particularly in regulating airflow through the syrinx, was studied in singing brown thrashers (Toxostoma rufum). In nine individuals, muscle activity was recorded electromyographically together with bilateral syringeal airflow, subsyringeal air sac pressure, and vocal output. 2. Dorsal muscles, m. syringealis dorsalis (dS) and m. tracheolateral dorsalis (dTB), are consistently activated during ipsilateral closing of the syrinx or increasing syringeal resistance, suggesting that their main role is adduction. This interpretation is supported by the motor patterns accompanying syllables with rapid oscillations in the rate of airflow. Bursts of electrical activity (2-10 ms) in dorsal muscles are precisely synchronized with decreasing airflow. 3. Electrical activity in m. tracheobronchialis ventralis (vTB) and m. tracheolateralis (TL) is associated with active abduction. An important contribution of vTB is to open the syringeal lumen for short inspirations in between syllables. In syllables with oscillatory flow modulations, vTB bursts show variable alignment with the phase of increasing flow. From this and activity during other syllables, it appears that, during phonation, vTB activity fine tunes the syringeal configuration, which is set by action of the dorsal muscles into a partially constricted state. 4. Activity in the ventral portion of TL, an extrinsic muscle, is strikingly similar to that of vTB, an intrinsic muscle, suggesting that the two muscles have a similar functional role. This supports the notion that intrinsic syringeal muscles of songbirds evolved from extrinsic muscles of nonpasserines. 5. M. syringealis ventralis (vS) does not appear to contribute directly to gating of airflow. Its activity is not consistently correlated with active changes in syringeal resistance. 6. Activity in m. sternotrachealis (ST) is most prominent during rapid changes in the rate of airflow or when switching between expiratory and inspiratory flow, suggesting a role in stabilizing the syringeal framework.

Animal Communication↗
PubMed1994

Motor dynamics of song production by mimic thrushes.

In brown thrashers (Toxostoma rufum) and grey catbirds (Dumetella carolinensis) neither side of the syrinx has a consistently dominant role in song production. During song, the two sides operate independently, but in close cooperation with each other and with the respiratory muscles which are capable of adjusting expiratory effort to maintain a constant rate of syringeal airflow despite sudden changes in syringeal resistance. Phonation is frequently switched from one side of the syrinx to the other, both between syllables and within a syllable. When both sides of the syrinx produce sound simultaneously, their respective contributions are seldom harmonically related. The resulting "two-voice" syllables sometimes contain difference tones with prominent sinusoidal amplitude modulation (AM). Rarely, both sides simultaneously produce the same sound. In general, however, the frequency range of sound contributed by the right syrinx is higher than that of the left syrinx. The right syrinx is also primarily responsible for producing a rapid cyclical amplitude modulation which is a characteristic feature of some syllables. This kind of AM is generated by either repetitive brief bursts of sound from the right side that modulate the amplitude of a continuous sound arising on the left side or cyclically opening the right syrinx, allowing unmodulated expiratory air to bypass the phonating left side.

Air Pressure↗
PubMed1994

Lateralization and motor stereotypy of song production in the brown-headed cowbird.

Song production in adult brown-headed cowbirds (Molothrus ater ater) is lateralized, with a slight right syringeal dominance. The left side of the syrinx produces low-frequency (200-2000 Hz) notes within the introductory note clusters, while the right side produces the higher-frequency (1500-6000 Hz) introductory notes, the interphrase unit (10-12 kHz), and the final high-frequency whistle (5-13 kHz). Cross-correlation analyses reveal that individual cowbirds produce each of their four to seven song types with a distinct stereotyped motor pattern--as judged by the patterns of syringeal airflow and subsyringeal pressure. The acoustic differences across song types are reflected in the differences in the bronchial airflow and air sac pressure patterns associated with song production. These motor differences are particularly striking within the second and third introductory note clusters where there is a rapid switching back and forth between the two sides of the syrinx in the production of notes. These motor skills may be especially important in producing behaviorally effective song.

Animals↗
PubMed1994

Variable asymmetry and resonance in the avian vocal tract: a structural basis for individually distinct vocalizations.

The social vocalizations of the oilbird (Steatornis caripensis) frequently have their acoustic energy concentrated into 3 prominent formants which appear to arise from the filter properties of their asymmetrical vocal tract with its bronchial syrinx. The frequency of the second and third formants approximate the predicted fundamental resonances of the unequal left and right cranial portions of each primary bronchus, respectively. Reversibly plugging either bronchus eliminates the corresponding formant. The first formant may arise in the trachea. The degree of vocal tract asymmetry varies between individuals, endowing them with different formant frequencies and providing potential acoustic cues by which individuals of this nocturnal, cave dwelling species may recognize each other in their dark, crowded colonies.

Animals↗
PubMed1990

Lateralization of syringeal function during song production in the canary.

The canary (Serinus canaria) vocal organ, the syrinx, has two separate sound sources, one in the cranial end of each bronchus. Previous investigations of whether song syllables are produced unilaterally or bilaterally have provided two contradictory results, as one researcher suggested that almost all syllables are produced by the left side of the syrinx alone, whereas another researcher suggested that both sides contribute similarly to all syllables. Our experiments, which involved unilateral bronchus plugging followed later by denervation of the ipsilateral syringeal muscles, attempted to resolve this disagreement. The males with right bronchus plugs, singing on the left side of the syrinx alone, produced nearly normal songs, whereas the birds with left bronchus plugs, singing on the right side, sang quite poorly. Interpretation of these data is difficult because it is not clear how syringeal function would be affected if the airflow rate through the intact side is increased above normal, nor is it known if the bird can compensate for bronchus occlusion. Nonetheless, we suggest that in male canaries most syllables are normally sung by the left side alone, with some syllables being produced by the right side alone and some being sung by both sides together. Right nerve section had little effect on the right-bronchus-plugged males' ability to sing, but the repertoires of the left-plugged males were altered after left nerve section, indicating the possibility that signals carried by the left nerve exert an influence on the contralateral side.

Animals↗
PubMed1988

The acoustic role of tracheal chambers and nasal cavities in the production of sonar pulses by the horseshoe bat, Rhinolophus hildebrandti.

The acoustic role of the enlarged, bony, nasal cavities and rigid tracheal chambers in the horseshoe bat, Rhinolophus hildebrandti (Fig. 2) was investigated by determining the effect of their selective filling on the nasally emitted sonar pulse and on the sound traveling backwards down the trachea. Normal sonar signals of this bat contain a long constant frequency component with most energy in the second harmonic at about 48 kHz. The fundamental is typically suppressed 20 to 30 dB below the level of the second harmonic (Fig. 1). None of the experimental manipulations described affected the frequency of the sonar signal fundamental. Filling the dorsal and both lateral tracheal chambers had little effect on the emitted vocalization, but caused the level of the fundamental component in the trachea to increase 15 to 19 dB in most bats (Table 2). When only the dorsal chamber or only the two lateral chambers were filled, the effect was less striking and more variable (Tables 3 and 4), suggesting that the tracheal fundamental is normally suppressed by acoustic interaction between these three cavities. Filling the enlarged dorsal nasal cavities had no effect on the tracheal sound. The effect of this treatment on the nasally emitted sonar pulse was inconsistent. Sometimes the fundamental increased 10 to 12 dB, other times the intensity of all harmonics decreased; in still other cases the second, third or fourth harmonic increased, but the fundamental remained unchanged (Tables 5, 6, and 7). When bats were forced to vocalize through the mouth, by sealing the nostrils, there was a prominent increase in the level of the emitted fundamental (10 to 21 dB) and in the fourth harmonic (6 to 17 dB). In one instance there was also a significant increase in the level of the third harmonic (Tables 8 and 9). The supraglottal tract thus filters the fundamental from the nasally emitted sonar signal, although the role of the inflated nasal cavities in this process is unclear. We conclude that a high glottal impedance acoustically isolates the subglottal from the supraglottal vocal tract. The tracheal chambers do not affect the emitted sonar signal, but may attenuate the fundamental in the trachea and prevent it from being reflected from the lungs back towards the cochlea. It may be important to prevent the reflected fundamental from stimulating the cochlea, via tissue conduction, along multiple indirect pathways which would temporally smear cochlear stimulation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

The sound emission pattern and the acoustical role of the noseleaf in the echolocating bat, Carollia perspicillata.

Carollia perspicillata (Phyllostomidae) is a frugivorous bat that emits low-intensity, broadband, frequency-modulated echolocation pulses through nostrils surrounded by a noseleaf. The emission pattern of this bat is of interest because the ratio between the nostril spacing and the emitted wavelength varies during the pulse, causing complex interference patterns in the horizontal dimension. Sound pressures around the bat were measured using a movable microphone and were referenced to those at a stationary microphone positioned directly in front of the animal. Interference between the nostrils was confirmed by blocking one nostril, which eliminated sidelobes and minima in the emission pattern, and by comparison of real emission patterns with simple computer models. The positions of minima in the patterns indicate effective nostril spacings of over a half-wavelength. Displacement of the dorsal lancet of the noseleaf demonstrated that this structure directs sound in the vertical dimension.

Acoustics↗
PubMed1966

Optomotor responses by echolocating bats.

Optomotor responses to moving stripes have been elicited from nine species of Microchiroptera. The minimum separable visual angle of two phyllostomids, under the experimental conditions, probably lies between 3.0 and 0.7 degrees; that of Myotis lucifugus, between 6.0 and 3.0 degrees. Four species indicate an ability to resolve stripes subtending 0.7 degree, the narrowest tested.

Animals↗