314 research outputs found
White-crowned sparrows tutored with syllable pairs can produce full songs
Journal ArticleDuring their 'sensitive period', young songbirds develop an 'acquired template', representing a memory of the song(s) that it hears. Later, during the sensorimotor phase, birds use this template to evaluate, via auditory feedback, their vocalizations
Superfast vocal muscles control song production in songbirds
Journal ArticleBirdsong is a widely used model for vocal learning and human speech, which exhibits high temporal and acoustic diversity. Rapid acoustic modulations are thought to arise from the vocal organ, the syrinx, by passive interactions between the two independent sound generators or intrinsic nonlinear dynamics of sound generating structures. Additionally, direct neuromuscular control could produce such rapid and precisely timed acoustic features if syringeal muscles exhibit rare superfast muscle contractile kinetics. However, no direct evidence exists that avian vocal muscles can produce modulations at such high rates
Superfast Vocal Muscles Control Song Production in Songbirds
Birdsong is a widely used model for vocal learning and human speech, which exhibits high temporal and acoustic diversity. Rapid acoustic modulations are thought to arise from the vocal organ, the syrinx, by passive interactions between the two independent sound generators or intrinsic nonlinear dynamics of sound generating structures. Additionally, direct neuromuscular control could produce such rapid and precisely timed acoustic features if syringeal muscles exhibit rare superfast muscle contractile kinetics. However, no direct evidence exists that avian vocal muscles can produce modulations at such high rates. Here, we show that 1) syringeal muscles are active in phase with sound modulations during song over 200 Hz, 2) direct stimulation of the muscles in situ produces sound modulations at the frequency observed during singing, and that 3) syringeal muscles produce mechanical work at the required frequencies and up to 250 Hz in vitro. The twitch kinematics of these so-called superfast muscles are the fastest measured in any vertebrate muscle. Superfast vocal muscles enable birds to directly control the generation of many observed rapid acoustic changes and to actuate the millisecond precision of neural activity into precise temporal vocal control. Furthermore, birds now join the list of vertebrate classes in which superfast muscle kinetics evolved independently for acoustic communication
Neurons Responsive to Global Visual Motion Have Unique Tuning Properties in Hummingbirds
Neurons in animal visual systems that respond to
global optic flow exhibit selectivity for motion direction and/or velocity. The avian lentiformis mesencephali (LM), known in mammals as the nucleus of the
optic tract (NOT), is a key nucleus for global motion
processing [1–4]. In all animals tested, it has been
found that the majority of LM and NOT neurons
are tuned to temporo-nasal (back-to-front) motion
[4–11]. Moreover, the monocular gain of the optokinetic response is higher in this direction, compared
to naso-temporal (front-to-back) motion [12, 13].
Hummingbirds are sensitive to small visual perturbations while hovering, and they drift to compensate for
optic flow in all directions [14]. Interestingly, the LM,
but not other visual nuclei, is hypertrophied in hummingbirds relative to other birds [15], which suggests
enhanced perception of global visual motion. Using
extracellular recording techniques, we found that
there is a uniform distribution of preferred directions
in the LM in Anna’s hummingbirds, whereas zebra
finch and pigeon LM populations, as in other tetrapods, show a strong bias toward temporo-nasal motion. Furthermore, LM and NOT neurons are generally
classified as tuned to ‘‘fast’’ or ‘‘slow’’ motion [10, 16,
17], and we predicted that most neurons would be
tuned to slow visual motion as an adaptation for
slow hovering. However, we found the opposite
result: most hummingbird LM neurons are tuned to
fast pattern velocities, compared to zebra finches
and pigeons. Collectively, these results suggest a
role in rapid responses during hovering, as well as
in velocity control and collision avoidance during forward flight of hummingbirds
600 MW FUSED SALT HOMOGENEOUS REACTOR POWER PLANT. Reactor Design and Feasibility Study
This report is a study of the feasibility of using a fused salt fuel reactor in a central station electric generating plant
Sexual Dimorphism of the Zebra Finch Syrinx Indicates Adaptation for High Fundamental Frequencies in Males
In many songbirds the larger vocal repertoire of males is associated with sexual dimorphism of the vocal control centers and muscles of the vocal organ, the syrinx. However, it is largely unknown how these differences are translated into different acoustic behavior.Here we show that the sound generating structures of the syrinx, the labia and the associated cartilaginous framework, also display sexual dimorphism. One of the bronchial half rings that position and tense the labia is larger in males, and the size and shape of the labia differ between males and females. The functional consequences of these differences were explored by denervating syringeal muscles. After denervation, both sexes produced equally low fundamental frequencies, but the driving pressure generally increased and was higher in males. Denervation strongly affected the relationship between driving pressure and fundamental frequency.The syringeal modifications in the male syrinx, in concert with dimorphisms in neural control and muscle mass, are most likely the foundation for the potential to generate an enhanced frequency range. Sexually dimorphic vocal behavior therefore arises from finely tuned modifications at every level of the motor cascade. This sexual dimorphism in frequency control illustrates a significant evolutionary step towards increased vocal complexity in birds
Visual Sensory Signals Dominate Tactile Cues during Docked Feeding in Hummingbirds
Animals living in and interacting with natural environments must monitor and respond to changing conditions and unpredictable situations. Using information from multiple sensory systems allows them to modify their behavior in response to their dynamic environment but also creates the challenge of integrating different, and potentially contradictory, sources of information for behavior control. Understanding how multiple information streams are integrated to produce flexible and reliable behavior is key to understanding how behavior is controlled in natural settings. Natural settings are rarely still, which challenges animals that require precise body position control, like hummingbirds, which hover while feeding from flowers. Tactile feedback, available only once the hummingbird is docked at the flower, could provide additional information to help maintain its position at the flower. To investigate the role of tactile information for hovering control during feeding, we first asked whether hummingbirds physically interact with a feeder once docked. We quantified physical interactions between docked hummingbirds and a feeder placed in front of a stationary background pattern. Force sensors on the feeder measured a complex time course of loading that reflects the wingbeat frequency and bill movement of feeding hummingbirds, and suggests that they sometimes push against the feeder with their bill. Next, we asked whether the measured tactile interactions were used by feeding hummingbirds to maintain position relative to the feeder. We created two experimental scenarios—one in which the feeder was stationary and the visual background moved and the other where the feeder moved laterally in front of a white background. When the visual background pattern moved, docked hummingbirds pushed significantly harder in the direction of horizontal visual motion. When the feeder moved, and the background was stationary, hummingbirds generated aerodynamic force in the opposite direction of the feeder motion. These results suggest that docked hummingbirds are using visual information about the environment to maintain body position and orientation, and not actively tracking the motion of the feeder. The absence of flower tracking behavior in hummingbirds contrasts with the behavior of hawkmoths, and provides evidence that they rely primarily on the visual background rather than flower-based cues while feeding
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