Processing of acoustic motion in the auditory cortex of the rufous horseshoe bat, Rhinolophus rouxi

This study investigated the representation of acoustic motion in different fields of auditory cortex of the rufous horseshoe bat, Rhinolophus rouxi. Motion in horizontal direction (azimuth) was simulated using successive stimuli with dynamically changing interaural intensity differences presented via earphones. The mechanisms underlying a specific sensitivity of neurons to the direction of motion were investigated using microiontophoretic application of γ-aminobutyric acid (GABA) and the GABAA receptor antagonist bicuculline methiodide (BMI). In the first part of the study, responses of a total of 152 neurons were recorded. Seventy-one percent of sampled neurons were motion-direction sensitive. Two types of responses could be distinguished. Thirty-four percent of neurons showed a directional preference exhibiting stronger responses to one direction of motion. Fifty-seven percent of neurons responded with a shift of spatial receptive field position depending on the direction of motion. Both effects could occur in the same neuron depending on the parameters of apparent motion. Most neurons with contralateral receptive fields exhibited directional preference only with motion entering the receptive field from the opposite direction (i.e. the ipsilateral part of the azimuth). Receptive field shifts were opposite to the direction of motion. Specific combinations of spatio-temporal parameters determined the motion-direction-sensitive responses. Velocity was not encoded as a specific parameter. Temporal parameters of motion and azimuthal position of the moving sound source were differentially encoded by neurons in different fields of auditory cortex. Neurons with a directional preference in the dorsal fields can encode motion with short interpulse intervals, whereas direction preferring neurons in the primary field can best encode motion with medium interpulse intervals. Furthermore, neurons with a directional preference in the dorsal fields are specialized for encoding motion in the midfield of azimuth, whereas direction preferring neurons in the primary field can encode motion in lateral positions. In the second part of the study, responses were recorded from additional 69 neurons. Microiontophoretic application of BMI influenced the motion-direction sensitivity of 53 % of neurons. In 21 % of neurons the motion-direction sensitivity was decreased by BMI by decreasing either directional preference or receptive field shift. In neurons with a directional preference, BMI increased the spike number for the preferred direction in about the same amount as for the non-preferred direction. Thus, inhibition was not direction specific. In contrast, BMI increased motion-direction sensitivity by either increasing directional preference or magnitude of receptive field shifts in 22 % of neurons. An additional 10 % of neurons changed their response from a receptive field shift to a directional preference under BMI. In these 32 % of neurons, the observed effects could often be better explained by adaptation of excitation than by inhibition. The results suggest, that motion information is differentially processed in different fields of the auditory cortex of the rufous horseshoe bat. Thus, functionally organized pathways for the processing of different parameters of auditory motion seem to exist. The fact that cortex specific GABAergic inhibition contributes to motion-direction sensitivity in at least a part of cortical neurons is supportive for the notion that the auditory cortex plays an important role in further processing the neural responses to apparent motion brought up from lower levels of the auditory pathway.In der vorliegenden Arbeit wurde die neuronale Repräsentation von akustischer Bewegungsinformation in verschiedenen Feldern des Hörkortex der Hufeisennasen- Fledermaus Rhinolophus rouxi untersucht. Bewegungen einer Schallquelle in der Horizontalebene wurden durch aufeinanderfolgende Stimuli mit sich dynamisch verändernden interauralen Intensitätsdifferenzen simuliert. Die Stimuli wurden über Ohrhörer dargeboten. Die Mechanismen die der Bewegungsrichtungsselektivität von Neuronen zu Grunde liegen, wurden mit Hilfe von mikroiontophoretischer Applikation von γ-Amino-buttersäure (GABA) und dem GABAA-Rezeptor Antagonisten Bicucullinmethiodid (BMI) untersucht. Im ersten Teil der Arbeit wurden Ableitungen von insgesamt 152 Neuronen erhalten. 71 % der Zellen waren bewegungsrichtungssensitiv. Dabei konnten zwei verschiedene Typen unterschieden werden: Bei 34 % aller Neurone zeigte sich eine Richtungsabhängigkeit in der Antwortamplitude. Die Zellen antworteten bevorzugt auf nur eine Bewegungsrichtung. Bei Zellen mit einem contralateralen rezeptiven Feld war dies eine Bewegung von der entgegengesetzten Seite (d.h. der ipsilateralen Seite) in das rezeptive Feld hinein. 57 % aller Neurone zeigten als richtungsabhängige Antwort eine Verschiebung der räumlichen Position des rezeptiven Feldes. Die Verschiebung war der Bewegungsrichtung entgegengesetzt. Beide Effekte konnten zusammen bei einer Nervenzelle beobachtet werden. Welcher der beiden Effekte auftrat, hing von den Parametern der Bewegung ab. Bestimmte Kombinationen von räumlichen und zeitlichen Bewegungsparametern bestimmten die Art der neuronalen richtungsabhängigen Antworten, die Bewegungsgeschwindigkeit wurde nicht als spezifische Größe in der Antwort kodiert. Zeitliche Parameter und die Position der Bewegung einer Schallquelle in der Horizontalebene wurden in verschiedenen Feldern des Hörkortex spezifisch verarbeitet. Neurone in den dorsalen Feldern zeigten ihre größte Richtungspräferenz bei Bewegungen mit kurzen Interpulsintervallen, wohingegen Zellen im primären Feld mittlere Interpulsintervalle bevorzugten. Weiterhin zeigten Neurone mit Richtungspräferenz in den dorsalen Feldern ihre maximale Antwort in mittleren Bereichen der Horizontalebene, während Zellen im primären Feld stärker auf seitliche Bereiche abgestimmt waren. Im zweiten Teil der vorliegenden Arbeit wurden die neuronalen Antworten von 69 weiteren Zellen abgeleitet. Die mikroiontophoretische Applikation von BMI beeinflußte das bewegungsrichtungssensitive Antwortverhalten von 53 % der Neurone. Bei 21 % der Zellen verringerte BMI die Bewegungsrichtungssensitivität. Es wurde entweder die Stärke der Richtungspräferenz oder die Größe der Verschiebung der räumlichen rezeptiven Felder verkleinert. Bei Zellen mit Richtungspräferenz erhöhte BMI die Antwortstärke für beide Bewegungsrichtungen in ungefähr dem gleichen Ausmaß. Es lag also keine richtungsspezifische Hemmung vor. Im Gegensatz dazu vergrößerte BMI bei 22 % der Neurone die Bewegungsrichtungssensitivität, entweder durch Vergrößerung der Richtungspräferenz oder durch Vergrößerung der Verschiebung der rezeptiven Felder. Weitere 10 % der Neurone veränderten ihre Antworteigenschaften durch BMI. Zeigten diese Zellen ohne BMI eine Verschiebung der räumlichen rezeptiven Felder, so konnte der Antworttyp mit BMI besser als Richtungspräferenz beschrieben werden. Bei diesen 32 % der Neurone konnten die beobachteten Effekte von BMI eher mit Adaptationsvorgängen erklärt werden, als durch den spezifischen Einfluß von GABAerger Hemmung. Die Ergebnisse lassen den Schluß zu, daß akustische Bewegungsinformation spezifisch in verschiedenen Feldern des Hörkortex von Rhinolophus rouxi verarbeitet wird. Es scheinen funktionell organisierte Verarbeitungswege für die verschiedenen Parameter akustischer Bewegungsinformation zu existieren. Die Tatsache, daß kortexspezifische Inhibition zumindest bei einem Teil der Neurone zur Bewegungsrichtungssensitivität beiträgt, unterstützt die Annahme, daß der Hörkortex eine wichtige Rolle bei der weiteren Verarbeitung der neuronalen Antworten auf bewegte Schallreize aus anderen Stationen der Hörbahn spielt

Regulation of the MAD1 promoter by G-CSF

MAD family proteins are transcriptional repressors that antagonize the functions of MYC oncoproteins. In particular, MAD1 has been demonstrated to interfere with MYC-induced proliferation, transformation and apoptosis. The MAD1 gene is expressed in distinct patterns, mainly associated with differentiation and quiescence. We observed that MAD1 is directly activated by G-CSF in promyelocytic cell lines. To investigate the transcriptional regulation of the human MAD1 gene, we have cloned and characterized its promoter. A region of high homology between the MAD1 orthologs of human, mouse and rat contains the core promoter, marked by open chromatin, high GC content and the lack of a TATA box. Using deletion constructs we identified two CCAAT-boxes occupied by C/EBPα and β in the homology region that mediate responsiveness to G-CSF receptor signaling. The necessary signals include the activation of STAT3 and the RAS/RAF/ERK pathway. STAT3 does not bind directly to promoter DNA, but is recruited by C/EBPβ. In summary, our studies provide a first analysis of the MAD1 promoter and suggest STAT3 functions as a C/EBPβ cofactor in the regulation of the MAD1 gene. Our findings provide the base for the characterization of additional signal transduction pathways that control the expression of MAD1

Communication breakdown: Limits of spectro-temporal resolution for the perception of bat communication calls

During vocal communication, the spectro‑temporal structure of vocalizations conveys important contextual information. Bats excel in the use of sounds for echolocation by meticulous encoding of signals in the temporal domain. We therefore hypothesized that for social communication as well, bats would excel at detecting minute distortions in the spectro‑temporal structure of calls. To test this hypothesis, we systematically introduced spectro‑temporal distortion to communication calls of Phyllostomus discolor bats. We broke down each call into windows of the same length and randomized the phase spectrum inside each window. The overall degree of spectro‑temporal distortion in communication calls increased with window length. Modelling the bat auditory periphery revealed that cochlear mechanisms allow discrimination of fast spectro‑temporal envelopes. We evaluated model predictions with experimental psychophysical and neurophysiological data. We first assessed bats’ performance in discriminating original versions of calls from increasingly distorted versions of the same calls. We further examined cortical responses to determine additional specializations for call discrimination at the cortical level. Psychophysical and cortical responses concurred with model predictions, revealing discrimination thresholds in the range of 8–15 ms randomization‑window length. Our data suggest that specialized cortical areas are not necessary to impart psychophysical resilience to temporal distortion in communication calls

A novel approach identifies the first transcriptome networks in bats: a new genetic model for vocal communication

Background: Bats are able to employ an astonishingly complex vocal repertoire for navigating their environment and conveying social information. A handful of species also show evidence for vocal learning, an extremely rare ability shared only with humans and few other animals. However, despite their potential for the study of vocal communication, bats remain severely understudied at a molecular level. To address this fundamental gap we performed the first transcriptome profiling and genetic interrogation of molecular networks in the brain of a highly vocal bat species, Phyllostomus discolor. Results: Gene network analysis typically needs large sample sizes for correct clustering, this can be prohibitive where samples are limited, such as in this study. To overcome this, we developed a novel bioinformatics methodology for identifying robust co-expression gene networks using few samples (N=6). Using this approach, we identified tissue-specific functional gene networks from the bat PAG, a brain region fundamental for mammalian vocalisation. The most highly connected network identified represented a cluster of genes involved in glutamatergic synaptic transmission. Glutamatergic receptors play a significant role in vocalisation from the PAG, suggesting that this gene network may be mechanistically important for vocal-motor control in mammals. Conclusion: We have developed an innovative approach to cluster co-expressing gene networks and show that it is highly effective in detecting robust functional gene networks with limited sample sizes. Moreover, this work represents the first gene network analysis performed in a bat brain and establishes bats as a novel, tractable model system for understanding the genetics of vocal mammalian communication

Communication breakdown : limits of spectro-temporal resolution for the perception of bat communication calls

Open Access funding enabled and organized by Projekt DEAL. This work was supported by the Human Frontier Science Program (Grant RGP0058 to UF).During vocal communication, the spectro-temporal structure of vocalizations conveys important contextual information. Bats excel in the use of sounds for echolocation by meticulous encoding of signals in the temporal domain. We therefore hypothesized that for social communication as well, bats would excel at detecting minute distortions in the spectro-temporal structure of calls. To test this hypothesis, we systematically introduced spectro-temporal distortion to communication calls of Phyllostomus discolor bats. We broke down each call into windows of the same length and randomized the phase spectrum inside each window. The overall degree of spectro-temporal distortion in communication calls increased with window length. Modelling the bat auditory periphery revealed that cochlear mechanisms allow discrimination of fast spectro-temporal envelopes. We evaluated model predictions with experimental psychophysical and neurophysiological data. We first assessed bats' performance in discriminating original versions of calls from increasingly distorted versions of the same calls. We further examined cortical responses to determine additional specializations for call discrimination at the cortical level. Psychophysical and cortical responses concurred with model predictions, revealing discrimination thresholds in the range of 8-15 ms randomization-window length. Our data suggest that specialized cortical areas are not necessary to impart psychophysical resilience to temporal distortion in communication calls.Publisher PDFPeer reviewe

Оптимизация условий для контроля качества наполнителя в металлических трубках

Проанализирована возможность с помощью цифровой радиографии контролировать качество наполнителя в детонирующем шнуре с целью обнаружения разноплотных включений, разрывов и других технологических нарушений. Проанализированы закономерности изменений интенсивности прошедшего потока квантов в геометрии узкого пучка. Определена энергия рентгеновского излучения, обеспечивающая максимальный перепад интенсивности прошедшего потока при изменении плотности наполнителя на +-30 %

Tip-surface forces, amplitude, and energy dissipation in amplitude-modulation (tapping mode) force microscopy

Amplitude-modulation (tapping mode) atomic force microscopy is a technique for high resolution imaging of a wide variety of surfaces in air and liquid environments. Here by using the virial theorem and energy conservation principles we have derived analytical relationships between the oscillation amplitude, phase shift, and average tip-surface forces. We find that the average value of the interaction force and oscillation and the average power dissipated by the tip-surface interaction are the quantities that control the amplitude reduction. The agreement obtained between analytical and numerical results supports the analytical method.This work has been supported by the Dirección General de Investigación Científica y Técnica (PB98-0471) and the European Union (BICEPS, BIO4-CT-2112). A. S. P. acknowledges financial support from the Comunidad Autónoma de Madrid.Peer reviewe

The influence of annealings on structure and microhardness of Fe-Mo-V-Nb-C steel processed by high-pressure torsion

The influence of high-pressure torsion on microstructure, microhardness and thermal stability of lowcarbon steel Fe-0,1Mo-0,6Mn-0,8Cr-0,2Ni-0,3Si-0,2Cu-0,1V-0,06Nb-0,09C, (wt.%) was investigated. It was shown that ultrafine-grained structure formed by high-pressure torsion possesses a high microhardness (H[mu]=7,0 GPa) and high thermal stability up to the temperature of 400°С