Biology subjects

Dietz, A.

Publications and source records attributed to Dietz, A..

4 recordsLinked to original sources

bioRxiv2023

Modeling and Simulation of Neocortical Micro- and Mesocircuitry. Part II: Physiology and Experimentation

Cortical dynamics underlie many cognitive processes and emerge from complex multi-scale interactions, which are challenging to study in vivo. Large-scale, biophysically detailed models offer a tool which can complement laboratory approaches. We present a model comprising eight somatosensory cortex subregions, 4.2 million morphological and electrically-detailed neurons, and 13.2 billion local and mid-range synapses. In silico tools enabled reproduction and extension of complex laboratory experiments under a single parameterization, providing strong validation. The model reproduced millisecond-precise stimulus-responses, stimulus-encoding under targeted optogenetic activation, and selective propagation of stimulus-evoked activity to downstream areas. The models direct correspondence with biology generated predictions about how multiscale organization shapes activity; for example, how cortical activity is shaped by high-dimensional connectivity motifs in local and mid-range connectivity, and spatial targeting rules by inhibitory subpopulations. The latter was facilitated using a rewired connectome which included specific targeting rules observed for different inhibitory neuron types in electron microscopy. The model also predicted the role of inhibitory interneuron types and different layers in stimulus encoding. Simulation tools and a large subvolume of the model are made available to enable further community-driven improvement, validation and investigation.

neuroscience↗

bioRxiv2023

Conserving bird populations in the Anthropocene: the significance of non-breeding movements

Advances in tracking technologies have revealed the diverse migration patterns of birds, which are critical for range mapping and population estimation. Population trends are usually estimated in breeding ranges where birds remain stationary, but for species that breed in remote areas like the Arctic, these trends are often assessed in over-wintering ranges. Evaluating population trends during the wintering season is challenging due to the extensive movements of birds in these ranges, which require a deep understanding of the movement dynamics. However, these movements remain understudied, particularly in the mid-latitudes, where many Arctic breeders overwinter, increasing uncertainty in their ranges and numbers. Here, we show that the Arctic breeding raptor Rough-legged buzzard, which overwinters in the mid-latitudes, has a specific wintering strategy. After migrating ca 1,500 km from the Arctic to mid-latitudes, the birds continue to move throughout the entire over-wintering period, covering an additional 1,000 km southwestward and then back northeastward as the snowline advances. This ongoing movement makes their wintering range dynamic over the course of the season. In essence, this movement represents an extension of the quick migration process, albeit at a slower pace, and we have termed this migration pattern foxtrot migration, drawing an analogy to the alternating fast and slow movements of the foxtrot dance. These results highlight the potential errors in range mapping from single mid-winter surveys and emphasize the importance of this migration pattern in assessing the conservation status of bird species. Understanding this migration pattern could help to correctly estimate bird populations in over-wintering ranges, which is especially important for species that nest in hard-to-reach regions such as the Arctic.

ecology↗

bioRxiv2022

Modeling and Simulation of Rat Non-Barrel Somatosensory Cortex. Part I: Modeling Anatomy

The function of the neocortex is fundamentally determined by its repeating microcircuit motif, but also by its rich, interregional connectivity. We present a data-driven computational model of the anatomy of non-barrel primary somatosensory cortex of juvenile rat, integrating whole-brain scale data while providing cellular and subcellular specificity. The model consists of 4.2 million morphologically detailed neurons, placed in a digital brain atlas. They are connected by 14.2 billion synapses, comprising local, mid-range and extrinsic connectivity. We delineated the limits of determining connectivity from neuron morphology and placement, finding that it reproduces targeting by Sst+ neurons, but requires additional specificity to reproduce targeting by PV+ and VIP+ interneurons. Globally, connectivity was characterized by local clusters tied together through hub neurons in layer 5, demonstrating how local and interegional connectivity are complicit, inseparable networks. The model is suitable for simulation-based studies, and a 211,712 neuron subvolume is made openly available to the community.

neuroscience↗

bioRxiv2022

Flower patterns improve foraging efficiency in bumblebees independent of nectary guidance

Colourful patterns on flowers are thought to benefit both pollinators and the plants they visit, by increasing the plants pollination success via an improved foraging efficiency of its pollinators. This increased efficiency is thought to result from a guidance effect of the flower patterns, correspondingly termed nectar guides, which indicate the position of the nectary to visiting pollinators. While it is well established that flower patterns play an important role in flower choice, the mechanisms underlying their function for flower-visiting insects remain poorly understood. In this study, we quantified the contributions of patterns to all phases of flower interaction in the buff-tailed bumblebee (Bombus terrestris). We analysed their flight paths, as well as landing positions and walking tracks on artificial flowers with different pattern types. We reveal that flower patterns improved the overall foraging efficiency of the bees by up to 30%, by guiding their approach flight, landing positions, and departure decisions. Surprisingly, these effects were not related to nectary guidance. Since we conducted the experiments with experienced foragers, which represent the majority of insect pollinators active in nature, the newly described nectary-independent guidance effects of flower patterns are of fundamental importance to plant-pollinator interactions under natural conditions.

ecology↗