Social interactions in natural populations of weakly electric fish

Animals and their sensory systems evolved in specific environments and in the context of their particular ethological niches. It is often found that sensory neurons are tuned to the statistics of the natural scenes that they likely to experience. Accordingly, the importance of knowledge of natural stimuli and the problems faced and solved by sensory systems in their natural environments for the understanding of neural processing is increasingly recognized. Weakly electric fish are successful model organisms for studying the neural mechanisms underlying sensory processing in vertebrates. These mostly nocturnal animals evolved an active electric sense employed in navigation, foraging and communication. Nocturnal conditions, murky water, and the tropical environment make their natural habitats challenging study sites. Therefore, most data on their natural behavior and their communication signals have been acquired under restricted lab conditions or remain anecdotal. However, their permanently active electric organ discharges provide an excellent opportunity to monitor the movements and communication of individual unrestrained fish. The central goal of the present thesis has been to establish and to apply a method for the non-invasive quantification of electrocommunication stimuli while animals roam and interact in their natural environment. In Chapter 2, we present an automated tracking system allowing for the reliable and continuous tracking of wave-type electric fish based on the individual-specific frequency of the electric organ discharge. The system extracts frequency modulations of the EOD on short and long time scales, and estimates location and orientation of the tracked fish. We acquired data on natural communication of the ghost knifefish, Apteronotus rostratus, during its reproductive period, by deploying our tracking system in the Panamanian rain forest (Chapter 3). We tracked individuals and characterized dyadic interactions and the corresponding electro-communication scenes. We showed that a specific communication signal, independent of context, was almost exclusively emitted in close proximity to a conspecific. During courtship, the communication of males was precisely locked to that of females. Our data also showed that competing male intruders can be detected and responded to over larger distances of up to 170 cm, even in the presence of a much stronger EOD of a nearby female conspecific. For the observed interactions we extracted frequency differences and estimated effective signal intensities, and related those to the response properties of the P-unit electro-receptors. Surprisingly, we found that in many relevant communication situations the electro-receptors will be driven only weakly by electric communication signals, either because of a frequency mismatch in courtship or because of large interaction distances in agonistic contexts. This study is the first account for the detailed monitoring and characterization of electric fish movement and communication in their natural habitat. To determine the behavioral context of the male-female interaction observed in Panamá, we conducted a long-term breeding experiment in the laboratory with the closely related species A. leptorhynchus (Chapter 4). We used our tracking software to identify male-female communication scenes similar to those observed in the field and demonstrated its relationship to courtship and spawning. Sequence and dynamics of the chirping during courtship closely matched that observed in the field. We found that both the female long chirp signaling spawning and the quick and precisely timed male echo response to female chirps are conserved across species. Applying our tracking system we revealed the properties of natural communication situations. We then demonstrated how our system can be used to further characterize the behaviors observed in the field in a tailor-made long-term laboratory study

Transparent Danionella translucida as a genetically tractable vertebrate brain model

Understanding how distributed neuronal circuits integrate sensory information and generate behavior is a central goal of neuroscience. However, it has been difficult to study neuronal networks at single-cell resolution across the entire adult brain in vertebrates because of their size and opacity. We address this challenge here by introducing the fish Danionella translucida to neuroscience as a potential model organism. This teleost remains small and transparent even in adulthood, when neural circuits and behavior have matured. Despite having the smallest known adult vertebrate brain, D. translucida displays a rich set of complex behaviors, including courtship, shoaling, schooling, and acoustic communication. In order to carry out optical measurements and perturbations of neural activity with genetically encoded tools, we established CRISPR-Cas9 genome editing and Tol2 transgenesis techniques. These features make D. translucida a promising model organism for the study of adult vertebrate brain function at single-cell resolution

Aspects of auditory signal transduction

Durch die Anwendung eines neuartigen Ansatzes ist es Gollisch et al. (2005) gelungen neue Einblicke in die Dynamik und Signalverarbeitung von auditorischen Rezeptorzellen zu liefern. In dieser Studie wurden mittels eines phänomenologischen Kaskadenmodells die linearen Filter und Nichtlinearitäten der auditorischen Signaltransduktion quantitativ allein aus der Kenntnis der Eingangsstimuli und der Ausgangs-Wahrscheinlichkeit, dass ein Aktionspotential (AP) ausgelöst wird, bestimmt. Die verwendete Methode beruht auf der Messung von sogenannten ”Iso-Response”-Kurven, die in anderem Kontext in der Psychophysik (z.B. Isophone in der Auditorik) verwendet werden. Bei diesem Ansatz werden die Stimulus-Parameter (s1, s2, ..., sn) dergestalt verändert, dass der Output des Systems konstant bleibt. Die gemessenen StimulusKonstellationen stellen Invarianzen dar, die das System nicht unterscheiden kann und enthüllen bei geeigneter Wahl der Stimuli System-spezifische Eigenschaften. In der Studie von Gollisch et al. (2005) wurden Paare kurzer akustischer Impulse (A1 , A2 ), sogenannte ”Clicks”, verwendet, die durch eine variable Zeit ∆t getrennt sind. Die Amplituden der Impulse wurden so justiert, dass die Wahrscheinlichkeit ein Aktionspotential auszulösen bei konstant 70% liegt. Die zeitliche Auflösung der Methode ist nur durch die Präzision des Stimulus begrenzt (ca. 10μs), und damit um ein Vielfaches höher als die zeitliche Variabilität der APs (ca. 1 ms). Durch die Messung solcher ”Iso-Response Sets” (IRS) für verschiedene Zeiten ∆t kann auf diese Weise eine hochaufgelöste ”Karte” der sogenannten ”effektiven Stimulusstärke” erstellt werden. Mithilfe mehrerer solcher Datensätze für unterschiedliche Stimuli lassen sich die funktionalen Filtereigenschaften der auditorischen Signaltransduktion berechnen. Diese Diplomarbeit beginnt mit einer Einleitung in den mathematischen Rahmen der Methode und setzt dann mit der Reproduktion der oben genannten Studie mit Hilfe numerischer Simulationen fort. Wir untersuchen, wie die Ergebnisse der IRS interpretiert werden müssen und stellen durch den Vergleich der Modelparameter mit den Messungen fest, dass nur ein Teil der effektiven Stimulusstärke durch die Methode erfasst wird. Die Begründung für diese Eigenschaft wird durch eine Untersuchung des mathematischen Rahmens der Methode geliefert. Wir zeigen dann auf, dass die Unterscheidung der linearen Filter des Kaskadenmodells darauf beruht, dass der Zeitverlauf des ersten linearen Filters kürzer ist als der des zweiten linearen Filters. Durch die Simulation von vollständigen AP-Generatoren, wie sie im Neuron z.B. am Axonhügel zu finden sind, zeigen wir, dass die Methode alle integrativen Eigenschaften des AP-Generators erfasst, sofern dessen Dynamik langsamer ist als die der vorangehenden Prozesse. In diesem Zusammenhang zeigen wir auch, das dass unter Umständen die Dynamik des Spike-Generators einen störenden Einfluss auf die Messung der Filtereigenschaften haben kann. Weiterhin zeigen wir, dass die Messung einer anderen Art von IRS im ”Amplituden-Raum” der Stimulus-Paare zu verschiedenen ∆t keine eindeutige Einsicht in die Natur der Input-Nichtlinearität liefert. Neben unseren Untersuchungen zur Interpretation von IRS, testen wir, ob es unter Umständen zu einer Trennung von funktionalen Filtermodulen durch den Einfluss von Rauschen kommt. Die von uns verwendeten Szenarien ergeben keine Hinweise auf ein solches Phänomen, so dass wir davon ausgehen müssen, dass alle Filtereigenschaften der zweiten Linearität des Kaskadenmodells durch die IRS erfasst werden. Schließlich setzen wir die unsere Ergebnisse in einen größeren Zusammenhang und diskutieren welchen Aufschluss uns die IRS über tatsächlich bestehende biophysikalische Mechanismen gibt

Prevalence of mental distress among adult survivors of childhood cancer in Germany—Compared to the general population

Abstract Background Increasing survival rates after childhood cancer have raised the issue of long‐term mental health consequences in adulthood. This study determines mental health distress among long‐term survivors of pediatric cancer and compares it to control groups. Methods Childhood cancer survivors (CCS; N = 951, aged 24‐49 years) were compared to three age‐matched control groups from the general population collected at three time points. The study compared the prevalence of clinically relevant symptoms of a wide range of common mental disorders (depression, somatic distress, suicidal ideation, generalized anxiety, panic, social anxiety, and sleep disturbances) using identical, validated questionnaires. CCS were identified by the German Childhood Cancer Registry. Controls were approached by a demographic consultation company (USUMA) which assured that the three samples were nationally representative. Results Childhood cancer survivors reported higher education than controls and were less often married. All forms of common mental distress were increased among survivors. Twenty‐four percent of male (N = 526) and 41% of female survivors (N = 425) reported some form of clinically relevant mental health symptoms. Somatic distress as the leading complaint was highly frequent among CCS (OR: 10.98, CI 95%: 7.24‐16.64). Complaints by generalized anxiety (OR: 5.04, CI 95%: 2.61‐9.70), panic (OR: 3.28, CI 95%: 1.60‐6.70), depression (OR: 3.36, CI 95%: 2.22‐5.09), and suicidality (OR = 2.22; CI 95%: 1.38‐3.57) were also strongly increased. Female sex, low education, low income, and unemployment were associated with increased distress. Conclusions Findings indicate a need to integrate psycho‐oncological screening and care into long‐term aftercare. Somatic distress, as cause and indicator of psychological distress, should receive stronger attention, especially tiredness, low energy, and pain

Austrian consensus guidelines on imaging requirements prior to hepatic surgery and during follow-up in patients with malignant hepatic lesions

Rapid advances in imaging technology have improved the detection, characterization and staging of colorectal liver metastases, hepatocellular carcinoma and cholangiocarcinoma. A variety of imaging modalities are available and play a pivotal role in the work-up of patients, particularly as imaging findings determine resectability. Surgery often represents the only measure that can render long-term survival possible. Imaging is also indispensable for the assessment of responses to neoadjuvant treatment and for the detection of recurrence. At a consensus meeting held in June 2017 in Vienna, Austria, Austrian experts in the fields of surgery and radiology discussed imaging requirements prior to and after hepatic surgery for malignant liver lesions. This consensus was refined by online voting on a total of 47 items. Generally, the degree of consensus was high. The recommendations relate to the type of preferred preoperative imaging modalities, technical settings with respect to computed tomography and magnetic resonance imaging, use of contrast agents, reporting, postoperative follow-up, and long-term follow-up. Taking local resources into account, these consensus recommendations can be implemented in daily clinical practice at specialized centers as well as outpatient diagnostic institutes in Austria.(VLID)360171