Disrupting vagal feedback affects birdsong motor control.

Coordination of different motor systems for sound production involves the use of feedback mechanisms. Song production in oscines is a well-established animal model for studying learned vocal behavior. Whereas the online use of auditory feedback has been studied in the songbird model, very little is known about the role of other feedback mechanisms. Auditory feedback is required for the maintenance of stereotyped adult song. In addition, the use of somatosensory feedback to maintain pressure during song has been demonstrated with experimentally induced fluctuations in air sac pressure. Feedback information mediating this response is thought to be routed to the central nervous system via afferent fibers of the vagus nerve. Here, we tested the effects of unilateral vagotomy on the peripheral motor patterns of song production and the acoustic features. Unilateral vagotomy caused a variety of disruptions and alterations to the respiratory pattern of song, some of which affected the acoustic structure of vocalizations. These changes were most pronounced a few days after nerve resection and varied between individuals. In the most extreme cases, the motor gestures of respiration were so severely disrupted that individual song syllables or the song motif were atypically terminated. Acoustic changes also suggest altered use of the two sound generators and upper vocal tract filtering, indicating that the disruption of vagal feedback caused changes to the motor program of all motor systems involved in song production and modification. This evidence for the use of vagal feedback by the song system with disruption of song during the first days after nerve cut provides a contrast to the longer-term effects of auditory feedback disruption. It suggests a significant role for somatosensory feedback that differs from that of auditory feedback.

Acquisition of an acoustic template leads to refinement of song motor gestures.

Vocal learning, a key behavior in human speech development, occurs only in a small number of animal taxa. Ontogeny of vocal behavior in humans and songbirds involves acquisition of an acoustic model, which guides the development of self-generated vocalizations (sensorimotor period). How vocal development proceeds in the absence of an acoustic model is largely unknown and cannot be studied directly in humans. Here we explored the effects of an acoustic model on song motor control by comparing peripheral motor gestures (respiration and syringeal muscles) of tutored birds with those of birds raised in acoustic isolation. Although the overall use of syringeal muscles during song was similar in both groups, tutored birds displayed enhanced temporal patterns of activation in respiratory and syringeal motor gestures. Muscle activation was more uniformly distributed throughout the song of tutored birds than that of untutored birds. Similarly, the respiratory effort was similar for both groups, but the expiratory pulses of song contained more modulations and temporal complexity in tutored birds. These results indicate that the acquisition of an acoustic template guides a refinement of experience-independent motor gestures by increasing temporal fine structure, but there is no difference in bilateral activation patterns for a given sound between the two groups. Nevertheless, these subtle temporal changes in muscle activation give rise to pronounced acoustic differences between the songs of the tutored and untutored birds. Experience with song during ontogeny therefore guides a more refined use of experience-independent motor programs.

Electroless gold island thin films: photoluminescence and thermal transformation to nanoparticle ensembles.

Electroless gold island thin films are formed by galvanic replacement of silver reduced onto a tin-sensitized silica surface. A novel approach to create nanoparticle ensembles with tunable particle dimensions, densities, and distributions by thermal transformation of these electroless gold island thin films is presented. Deposition time is adjusted to produce monomodal ensembles of nanoparticles from 9.5 +/- 4.0 to 266 +/- 22 nm at densities from 2.6 x 1011 to 4.3 x 108 particles cm-2. Scanning electron microscopy and atomic force microscopy reveal electroless gold island film structures as well as nanoparticle dimensions, densities, and distributions obtained by watershed analysis. Transmission UV-vis spectroscopy reveals photoluminescent features that suggest ultrathin EL films may be smoother than sputtered Au films. X-ray diffraction shows Au films have predominantly (111) orientation.