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Predictive mechanisms in passive and active touch
(2025-10) Jeschke, Michaela
Perception is an active process which is shaped by prior sensory experiences and expectations about the objects and situational demands that an agent is confronted with. The first part of this work focuses on neural adaptation processes in passive tactile perception, while the second part will examine the role of prior visual information and different context factors for optimization of active haptic explorations. In the first study we exploited tactile adaptation aftereffects to reveal previously unknown communalities in the somatosensory processing of spatially structured tactile features. Two-point distance, macro-scale roughness, and curvature have been extensively studied in isolation in the past and are deemed critical for shape and material perception. Their potential overlap in sensory processing however had remained unexplored. Across four experiments, we here demonstrate that adaptation to one property can produce aftereffects in the perception of the other properties: For roughness and tactile distance specifically, cross property aftereffects were bidirectional, specific to orientation and skin region, weaker than the respective within-property aftereffects, and did not result from peripheral receptor fatigue. Together, the results suggest a common neural substrate for processing spatially structured tactile features at early cortical levels, providing a window into how low-level spatial features may be organized to support coherent object perception. A second study compliments the first one: here, we investigated whether there is a relationship between biophysical skin properties with basic tactile abilities and the tactile distance aftereffect. While previous studies clearly demonstrated that peripheral factors are not the origin and cause of tactile aftereffects, it had remained unclear whether they could have an additional impact on aftereffect expression, possibly explaining interindividual differences in e.g. the aftereffect strength. Results revealed that higher hydration and elasticity were related to increased tactile sensitivity and spatial acuity. The magnitude of distance aftereffects, however, was independent from both skin properties and tactile abilities; suggesting that the underlying cortical processes are rather robust and stable. Interindividual variability in the aftereffect magnitude might instead stem from e.g. cortical idiosyncrasies causing differences in the susceptibility to neural adaptation. For active touch, we examined in the third study if and how prior visual information can be exploited for texture exploration. Participants had to discriminate grating textures by spatial frequency while receiving prior visual cues of varying quality about texture orientation. These priors influenced exploratory movement direction similarly to adjustments known to emerge during exploration and to enhance perception, but notably, they did so already at initial contact. The degree of adjustment scaled with the quality, i.e. informational value of the priors, consistent with established motor control models. The findings show that humans can flexibly learn to use abstract visual priors to optimize haptic explorations, with the learning process and direct usage substantially depending on the priors’ quality. In the fourth study, we corroborated and extended findings from study 3 with an investigation in a more naturalistic VR-setting, assessing haptic exploration of real-life materials (sand, sponge, sandpaper), and how naturalistic prior visual information affects the initial movement selection beyond single movement parameter adjustment but with regard to holistic movement selection. Results showed that with adequate prior visual information, participants explored materials in a more efficient way: they used specialized exploratory procedures earlier, with higher probability, and explored materials for a shorter time. In the fifth study, we assessed factors that humans might take into account for termination of exploratory behavior. (Expected) task demands are known to influence, e.g., force tuning in softness exploration. Exploration extension generally improves discrimination performance up to a saturation point. We therefore hypothesized that humans adjust exploration durations according to current task demands and assessed this in a haptically rendered grating discrimination task. However, exploration extension increases motor costs, which humans typically seek to minimize; to examine the role of motor costs for haptic explorations, we artificially manipulated motor effort by implementing counteracting forces in a force-feedback device. Results showed that increased task demands were compensated by exploration extension, but the extent of this compensation depended on the motor costs the agent was confronted with. This likely reflects the agent’s dynamically updated cost-benefit expectations. Altogether, this dissertation provides new behavioral evidence on how efficiency of touch perception is supported by robust early cortical mechanisms jointly encoding different tactile features, as well as higher-level prediction processes that enable exploratory movement adjustments for optimized sensory data gathering.
„Es gab wunderbares Material unter diesen Gehirnen“: Hirnforschung im Kontext der „Euthanasie“, die Max-Planck-Gesellschaft und einige Fragen zur Ethik medizinischer Forschung
(2026-02-20) Roelcke, Volker
(Uncovering Medicine)
Einfluss einer kranial eingebrachten Schraube auf die Verformung und damit auf die Primärstabilität von zementfreien Hüftpfannen - eine in vitro Analyse
(2025) Breidenbach, Salome Loisa Zoe
Die Hauptursache für Revisionen von Hüftendoprothesen ist die aseptische Lockerung. Ein wichtiger Faktor, um diese Komplikation bei zementfreien Implantaten zu verhindern, ist eine gute Osteointegration. Grundlage hierfür ist die Primärstabilität insbesondere der acetabulären Komponente. Bei der Hüftpfanne soll das zusätzliche Einbringen einer kranialen Schraube für mehr Stabilität sorgen. Allerdings ist vorstellbar, dass das Implantat durch den punktuellen Druck der Schraube verformt werden und damit die Kongruenz des Implantats mit dem vorher gefrästen Knochen nicht mehr gegeben sein könnte. Hierdurch könnte wiederum die Primärstabilität beeinflusst werden. Diese potenzielle Verformung und ihr Einfluss auf die Primärstabilität im Knochen sollen in dieser in vitro Analyse in fünf verschiedenen Presspassungs-Hüftpfannen untersucht werden. Die Hüftpfannen wurden in ein Kunstknochenmodell implantiert und unter Einleitung von Drehmomenten, die den physiologischen Gang simulieren, auf Primärstabilität in Form von Mikrorelativbewegung des Implantats in Relation zum Knochenmodell geprüft. Anschließend wurde während des Einbringens der kranialen Schraube von Hand durch in die Pfanne eingeklebte hochauflösende Messfühler die Verformung der verschiedenen Pfannen und daraufhin erneut die Primärstabilität gemessen. Bei allen Hüftpfannen zeigte sich beim Einbringen der Schraube eine Verformung. Die Mikrorelativbewegung nach Einbringen der Schraube sank im Mittelwert bei der REVISIO S SYSTEM®, Ecofit® and EPORE® und stieg bei der Allofit® and DELTA TT® an. Diese Unterschiede waren allerdings nicht signifikant. Ein signifikanter Zusammenhang zwischen dem Ausmaß der Verformung und der Veränderung der Mikrorelativbewegung ließ sich daher nicht feststellen. Da der gewünschte Effekt einer verbesserten Primärstabilität durch das Einbringen einer Schraube bei zwei der fünf Pfannenmodelle nicht eintrat, sondern sich die Primärstabilität im Mittel sogar verringerte, sollte der Nutzen dieser Schraube Inhalt weiterer Untersuchungen sein, um unnötige Operationsschritte und ein erhöhtes Risiko für aseptische Lockerungen zu vermeiden. Ebenfalls sollte ein möglicher Effekt der ermittelten Vorformung der Implantate durch das Einbringen einer kranialen Schraube auf das Ergebnis des Eingriffs weiter überprüft werden.
Increasing microplastic concentrations have nonlinear impacts on the physiology of reef-building corals
(2025) Tirpitz, Vanessa; Hutter, Mona; Hutter, Hanna; Prume, Julia; Koch, Martin; Wilke, Thomas; Reichert, Jessica
The pollution of marine environments with plastics, particularly microplastic (MP, i.e., plastic particles <5 mm), is a major threat to marine biota, including corals. While the effects of MPs are increasingly well understood, knowledge of how different concentrations of naturally occurring MP mixtures affect reef-building corals is still limited. Therefore, we aimed to elucidate the relationship of MP concentrations and their effects on reef-building corals. For this, we exposed two reef-building coral species (Stylophora pistillata and Pocillopora verrucosa) in a 12-week experiment to MPs at a gradient of concentrations (0, 0.1, 1, 10, and 100 mg⋅L􀀀 1). Specifically, we examined effects on the coral host physiology (i.e., surface and volume growth, calcification, necrosis, and polyp activity), and the photosynthetic activity of the photosymbionts (i.e., effective and maximum quantum yield, maximum relative electron transport rate, minimum saturating irradiance, and light capture efficiency). To mimic natural conditions, we used a MP mixture consisting of six polymers in forms of fibers and fragments. Both coral species showed reduced growth rates, necrosis, lower polyp activity, and an upregulation of photosynthesis, which intensified with increasing MP concentrations. While the effects on the coral host mostly showed basic linear or nonlinear dose-response relationships, the effects on the photosymbionts revealed more complex nonlinear dose-response relationships, and photosynthesis was only upregulated after a species-specific threshold. We found that high and extreme pollution scenarios caused strong adverse effects on coral physiology, while current low to moderate concentrations had minor effects. Increasing concentrations had amplifying effects, likely due to the disproportionately higher frequency of entanglement, leading to more frequent direct contact and potential transfer of toxins or pathogens. These results suggest that corals can cope with current average pollution levels. However, they also highlight the need for measures to limit permanent increases of MP pollution to protect the health of coral reefs.
Data for "London Dispersion Favors cis-Selectivity in the Johnson-Corey-Chaykovsky Epoxidation"
(2026-02-13) Domanski, Marvin H. J.
Contains 1H and 13C Data for all new compounds (as listed below) to accompany 'London Dispersion Favors cis-Selectivity in the Johnson-Corey-Chaykovsky Epoxidation' 1-[(3,5-Diethylphenyl)methyl] tetrahydrothiophenium tetrafluoroborate 1-[(3,5-Di-iso-propyl-phenyl)methyl] tetrahydrothiophenium tetrafluoroborate 1-[(3,5-Dimethylphenyl)methyl] tetrahydrothiophenium tetrafluoroborate 1-[(3,5-Di-tert-butyl-phenyl)methyl] tetrahydrothiophenium tetrafluoroborate 1-[(Phenyl)methyl]tetrahydrothiophenium tetrafluoroborate Anti-1,2-Bis[3,5-di-tert-butyl]phenyl-2-hydroxyethyl(dimethyl) sulfonium iodide Syn-1,2-Bis[3,5-di-tert-butyl]phenyl-2-hydroxyethyl(dimethyl) sulfonium iodide filename format (in order): (1H or 13C NMR) - Compound name data format (as separated rows): chemical shift, Intensity