Freely-moving mice visually pursue prey using a retinal area with least optic flow

Mice have a large visual field that is constantly stabilized by vestibular ocular reflex driven eye rotations that counter head-rotations. While maintaining their extensive visual coverage is advantageous for predator detection, mice also track and capture prey using vision. However, in the freely moving animal quantifying object location in the field of view is challenging. Here, we developed a method to digitally reconstruct and quantify the visual scene of freely moving mice performing a visually based prey capture task. By isolating the visual sense and combining amouse eye optic model with the head and eye rotations, the detailed reconstruction of the digital environment and retinal features were projected onto the corneal surface for comparison, and updated throughout the behavior. By quantifying the spatial location of objects in the visual scene and their motion throughout the behavior, we show that the image of the prey is maintained within a small area, the functional focus, in the upper-temporal part of the retina. This functional focus coincides with a region of minimal optic flow in the visual field and consequently minimal motion-induced image blur during pursuit, as well as the reported high density-region of Alpha-ON sustained retinal ganglion cells

WRB- Klassifizierung von Tonverlagerungsböden im Gelände mittels Gammastrahlungssignaturen in Nordthailand

Die Tonverlagerung ist der wichtigste bodenbildende Prozess in Nordthailand (Schuler 2008). In Abhängigkeit von Petrographie, Topographie und Klima kommt es im Wesentlichen zur Bildung von Acrisolen und Alisolen, untergeordnet treten daneben auch Luvsiole und Lixisole auf. Entsprechend der WRB 2006 Klassifikation (World Reference Base for Soil Resources IUSS Working Group WRB 2006) lassen sich diese Referenzbodengruppen nur anhand der Kationenaustauschkapazität des Tons und der Basensättigung voneinander unterscheiden. Der erste Parameter lässt sich jedoch nur durch zeitraubende und kostenintensive Analysen bestimmen, was für Bodenkartierer unbefriedigend ist, da diese Information schon im Feld sehr hilfreich sein kann. Das Ziel dieser Arbeit besteht darin, herauszufinden, ob sich Tonverlagerungsböden anhand ihrer Gammastrahlungssignaturen bereits im Feld voneinander unterscheiden lassen. Zugrunde liegt hier die Annahme, dass unterschiedliche Tonverlagerungsböden eine spezifische Tonmineralzusammensetzung aufweisen, welche sich in der Geochemie und folglich in der Gammastrahlungssignatur widerspiegelt. Sowohl die bodenbasierte als auch die luftgestützte Messung der Gammastrahlung von Ton-verlagerungsböden über Kalkstein ergab höchst signifikant unterschiedliche Strahlungssignaturen für K, eU, und eTh. Insbesondere die K- und eTh-Signaturen erlaubten eine deutliche Trennung von Acrisolen und Alisolen. Sollten sich die Messungen auch an anderen Lokalitäten und bei anderem Ausgangsgestein wiederholen lassen, dann ließen sich zukünftig mehr Tonverlagerungsböden mit einem tragbaren Strahlungsmessgerät und pH-Meter bereits im Feld voneinander unterscheiden. Zur Kartierung größerer Areale kann theoretisch eine Klassifizierung durch luftgestützte Messungen vorgenommen werden. Damit könnten enorme Analysenkosten eingespart werden

Visual pursuit behavior in mice maintains the pursued prey on the retinal region with least optic flow

Mice have a large visual field that is constantly stabilized by vestibular ocular reflex (VOR) driven eye rotations that counter head-rotations. While maintaining their extensive visual coverage is advantageous for predator detection, mice also track and capture prey using vision. However, in the freely moving animal quantifying object location in the field of view is challenging. Here, we developed a method to digitally reconstruct and quantify the visual scene of freely moving mice performing a visually based prey capture task. By isolating the visual sense and combining a mouse eye optic model with the head and eye rotations, the detailed reconstruction of the digital environment and retinal features were projected onto the corneal surface for comparison, and updated throughout the behavior. By quantifying the spatial location of objects in the visual scene and their motion throughout the behavior, we show that the prey image consistently falls within a small area of the VOR-stabilized visual field. This functional focus coincides with the region of minimal optic flow within the visual field and consequently area of minimal motion-induced image-blur, as during pursuit mice ran directly toward the prey. The functional focus lies in the upper-temporal part of the retina and coincides with the reported high density-region of Alpha-ON sustained retinal ganglion cells.Mice have a lot to keep an eye on. To survive, they need to dodge predators looming on land and from the skies, while also hunting down the small insects that are part of their diet. To do this, they are helped by their large panoramic field of vision, which stretches from behind and over their heads to below their snouts. To stabilize their gaze when they are on the prowl, mice reflexively move their eyes to counter the movement of their head: in fact, they are unable to move their eyes independently. This raises the question: what part of their large visual field of view do these rodents use when tracking a prey, and to what advantage? This is difficult to investigate, since it requires simultaneously measuring the eye and head movements of mice as they chase and capture insects. In response, Holmgren, Stahr et al. developed a new technique to record the precise eye positions, head rotations and prey location of mice hunting crickets in surroundings that were fully digitized at high resolution. Combining this information allowed the team to mathematically recreate what mice would see as they chased the insects, and to assess what part of their large visual field they were using. This revealed that, once a cricket had entered any part of the mices large field of view, the rodents shifted their head - but not their eyes - to bring the prey into both eye views, and then ran directly at it. If the insect escaped, the mice repeated that behavior. During the pursuit, the crickets position was mainly held in a small area of the mouses view that corresponds to a specialized region in the eye which is thought to help track objects. This region also allowed the least motion-induced image blur when the animals were running forward. The approach developed by Holmgren, Stahr et al. gives a direct insight into what animals see when they hunt, and how this constantly changing view ties to what happens in the eyes. This method could be applied to other species, ushering in a new wave of tools to explore what freely moving animals see, and the relationship between behaviour and neural circuitry

Gammaspektrometrie - eine vielversprechende Methode zur Feldbestimmung und luftgestützten Erkundung von Böden

In der vorliegenden Studie wird die Eignung der Gammaspektroskopie zur Kartierung von Böden sowohl im Feld, als auch luftgestützt getestet. Die Pilotstudie hierfür erfolgte im Kalksteingebiet Bor Krai, Mae Hong Son Provinz, Nordthailand. Kalkstein als dominantes Ausgangsgestein wurde ausgewählt, da dieser nur eine sehr geringe Eigenstrahlung aufweist und somit nicht mit der Bodenmessung interferiert. In Abhängigkeit von Petrographie, Topographie und Klima treten im Arbeitsgebiet hauptsächlich Acrisole und Alisole auf. Entsprechend der WRB 2006 Bodenklassifikation lassen sich diese beiden Referenzbodengruppen nur anhand der Kationenaustauschkapazität des Tons und der Basensättigung voneinander unterscheiden. Während die Basensättigung durch eine pH Feldmessung abgeschätzt werden kann, ist die Bestimmung der Kationenaustauschkapazität des Tons nur durch kostspielige und zeitaufwendige Laboranalysen zu bestimmen. Durch die Nutzung des Verhältnisses von eTh (Thorium Equivalent) - zu K-Strahlungssignaturen ist es nun jedoch möglich, zumindest auf Kalkstein, diese beiden Böden mithilfe eines tragbaren Radiometers (Gf Instruments Gamma-Ray Spectrometer GRM-260 bzw. Gamma Surveyor), schon im Feld voneinander zu unterscheiden. Dabei zeigt sich, dass Acrisole ein eTh/K Verhältnis >16 haben, während Alisole Verhältniswerte <16 aufzeigen. Bei luftgestützten Messungen (256-Kanal, Kenting Gamma-Strahlungs-Spektrometer with NaI Kristall Detektor; 1km Abstand der Befliegungslinien, 120m Flughöhe) liegt der Grenzwert zur Unterscheidung von Acrisolen und Alisolen bei einem eTh/K Verhältnis von 12,5. Der Vergleich von interpretierten luftgestützten Punktmessdaten zweier Transekte, mit einer traditionell erstellten Bodenkarte zeigt eine hohe Übereinstimmung. Kleinere Abweichungen gab es lediglich in den Übergangszonen beider Böden, die sich teilweise auf Ungenauigkeiten in der Bodenkarte als auch auf Heterogenität im Ausgangsgestein zurückführen lassen. Eine Überprüfung mit interpretierten radiometrischen Bodenmesswerten für dieselben Transekte zeigte ebenfalls große Übereinstimmungen mit der Bodenkarte. Darüber hinaus konnten durch die radiometrischen Bodenmessungen kleinere Fehler der traditionell erstellten Bodenkarte aufgedeckt werden, die sich bei deren Erstellung aufgrund beschränkter Analysekapazität nicht vermeiden ließen. Die vorliegende Studie hat gezeigt, dass der Einsatz der Gammaspektroskopie die Qualität und Effizienz in der Bodenkartierung des untersuchten tropischen Kalksteingebietes erheblich verbessern konnte. Da es Hinweise für eine Übertragbarkeit der Anwendung auf andere Gebiete (Süddeutschland) gibt, ist für die Zukunft die Erkundung bei anderen Ausgangsgesteinen und in anderen Klimaten geplant

Short- and long-term effects of crop residues and of phosphorus fertilization on pearl millet yield on an acid sandy soil in Niger, West Africa

Field experiments were conducted during the rainy seasons of 1990 and 1991 on an acid sandy soil (Luvic Arenosol) in Niger, to assess long-term (since 1986) andshort-term (since 1990) effectsof millet straw (cropresidues) at different amounts (2 t and 6 t ha−1) and modes of application (incorporation, mulching and burning), andofphosphorus (P) fertilization on dry matter yield of pearl millet [Pennisetum glaucum (L.) R. Br.]. Especially long-term, but also short-term application ofcropresidues increased dry matter yield of pearl millet by more than 60%, whereas their omission decreased yield immediately. Compared to mulching or burning, higher yields were obtained with incorporation ofcropresidues. When cropresidues were applied as mulch, dry matter yield was increased to the same extent by 2 t and 6 t ha−1. Similar dry matter yields were achieved with cropresidues (-P) to those with P fertilizer only. An additional yield increase could be obtained by simultaneous application ofcropresiduesand P. Without cropresidues, potassium (K) concentrations in the shoot dry matter indicated K deficiency. With cropresidues considerable amounts of K (15 kg t−1) were provided and raised the K concentrations in the plants to the sufficiency range. Although with cropresidues some P was provided (1.5 kg t−1), the beneficial effects were primarily attributed to increased P acquisition by the millet plants, which was reflected in enhanced root growth in the topsoil (0–10 cm

Ultrasound settings significantly alter arterial lumen and wall thickness measurements

Background. Flow-mediated dilation (FMD) and carotid intima-medial thickness (CIMT), measured by ultrasound, are widely used to test the efficacy of cardioprotective interventions. Although assessment methods vary, automated edge-detecting image analysis software is routinely used to measure changes in FMD and CIMT. We aimed to quantify the effect that commonly adjusted ultrasound settings have on arterial lumen and wall thickness measurements made with CIMT measurement software. Methods. We constructed phantom arteries from a tissue-mimicking agar compound and scanned them in a water bath with a 10 MHz multi-frequency linear-array probe attached to a high-resolution ultrasound machine. B-mode images of the phantoms were recorded with dynamic range (DR) and gain set at five decibel (dB) increments from 40 dB to 60 dB and -10 dB to +10 dB respectively. Lumen diameter and wall-thickness were measured off-line using CIMT measurement software. Results. Lumen measurements: there was a strong linear relationship between DR and gain and measured lumen diameter. For a given gain level, a 5 dB increase in DR reduced the measured lumen diameter by 0.02 ± 0.004 mm (p \u3c 0.001). For a given DR level, a 5 dB increase in gain reduced measured lumen diameter by 0.04 ± 0.004 mm (p \u3c 0.001). A 5 mm increase in distance between the ultrasound probe and the artery reduced measured lumen diameter by 0.04 ± 0.03 mm (p \u3c 0.001). CIMT measurements: For a fixed gain level, a 5 dB increase in DR increased measured wall thickness by 0.003 ± 0.002 mm (p \u3c 0.001). The effects of increasing gain were not consistent and appeared to vary depending on the distance between the artery and the ultrasound probe and the thickness of the artery wall. Conclusion. DR, gain and probe distance significantly alter lumen diameter and CIMT measurements made using image analysis software. When CIMT and FMD are used to test the efficacy of cardioprotective interventions, the DR, gain and probe position used to record baseline scans should be documented and replicated in post-treatment scans in individual trial subjects. If more than one sonographer or imaging centre is used to collect data, the study protocol should document specific DR and gain settings to be used in all subjects