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12 results on '"Helmstädter, M.N."'

1. Large-scale connectomics in mouse barrel cortex

Author

Helmstädter, M.N., Laurent, G., Sievers, Meike, Helmstädter, M.N., Laurent, G., and Sievers, Meike

Abstract

Radboud University, 25 april 2023, Promotor : Helmstädter, M.N. Co-promotor : Laurent, G., Contains fulltext : 291016.pdf (Publisher’s version ) (Closed access), Volume electron microscopy (3D EM) has enabled dense mapping of the brain’s wiring diagram, the so-called connectome, at single-synapse resolution. The technological challenge in acquiring connectomes arises from the spatial scales which need to be bridged (10-6-10-5 to 10-1-100 mm). In mammalian brains, a cubic millimeter is considered the minimal target volume to capture a sufficient large number of sufficiently complete neurons, which is a prerequisite for comprehensive neuron-to-neuron network analyses. However, the effective imaging rate of conventional single-beam scanning EMs (SEMs) is ultimately limited by the scan speed of the electron beam, and previously reported dataset volumes have been restricted to a few hundred micrometer edge length. In this work experimental and computational methods for high-throughput multi-beam SEM (MultiSEM) combined with automated tape collecting ultramicrotomy (ATUM) are implemented and employed to acquire and analyze a millimeter scale connectomics dataset of the mouse barrel cortex encompassing complete cortical columns.

Published
2023

2. Connectomic comparison of the human and non-human primate cortex to mouse

Author

Helmstädter, M.N., Hua, Y., Loomba, S., Helmstädter, M.N., Hua, Y., and Loomba, S.

Abstract

Radboud University, 07 februari 2023, Promotor : Helmstädter, M.N. Co-promotor : Hua, Y., Contains fulltext : 288918.pdf (Publisher’s version ) (Closed access), Is the human brain simply a scaled-up version of the mouse brain? Sahil Loomba investigated the comparative aspects of structural connectivity in human, monkey and mouse brain using relatively novel three-dimensional electron microscopy technique. Sahil found evidence that the human nerve cells are composed of an increased number of interneurons that is two- to- three times higher compared to mouse. This, in effect, results in a massively increased connectivity between the inhibitory interneurons that is nearly absent in mouse. This, for the first time, points to a network innovation that is unique to the human cortical networks. This discovery encourages a new focus of studies on the functional relevance and impact of such connectivity features, with significance for fundamental as well as clinical neuroscience.

Published
2023

3. Neuronal and network mechanisms for

Author

Helmstädter, M.N., Gjorgjieva, Julijana, Shao, S., Helmstädter, M.N., Gjorgjieva, Julijana, and Shao, S.

Abstract

Radboud University, 14 juni 2023, Promotores : Helmstädter, M.N., Gjorgjieva, Julijana, Contains fulltext : 293084.pdf (Publisher’s version ) (Closed access)

Published
2023

4. Connectomic comparison of mouse and human cortex

Author

Loomba, Sahil, Straehle, Jakob, Gangadharan, Vijayan, Heike, Natalie, Khalifa, A.M.M., Motta, Alessandro, Meyer, Hanno S., Helmstädter, M.N., Sievers, Meike, Loomba, Sahil, Straehle, Jakob, Gangadharan, Vijayan, Heike, Natalie, Khalifa, A.M.M., Motta, Alessandro, Meyer, Hanno S., Helmstädter, M.N., and Sievers, Meike

Abstract

Contains fulltext : 252242.pdf (Publisher’s version ) (Closed access)

Published
2022

5. The role of temporal neocortex in threat memory

Author

Helmstädter, M.N., Letzkus, M., Dalmay, T., Helmstädter, M.N., Letzkus, M., and Dalmay, T.

Abstract

Radboud University, 24 november 2020, Promotor : Helmstädter, M.N. Co-promotor : Letzkus, M., Contains fulltext : 226301.pdf (publisher's version ) (Open Access)

Published
2020

8. webKnossos: efficient online 3D data annotation for connectomics

Author

Boergens, Kevin M., Berning, Manuel, Bocklisch, Tom, Bräunlein, Dominic, Drawitsch, F.P., Frohnhofen, Johannes, Herold, Tom, Otto, Philipp, Rzepka, Norman, Werkmeister, Thomas, Werner, Daniel, Wiese, Georg, Wissler, Heiko, Helmstädter, M.N., Boergens, Kevin M., Berning, Manuel, Bocklisch, Tom, Bräunlein, Dominic, Drawitsch, F.P., Frohnhofen, Johannes, Herold, Tom, Otto, Philipp, Rzepka, Norman, Werkmeister, Thomas, Werner, Daniel, Wiese, Georg, Wissler, Heiko, and Helmstädter, M.N.

Abstract

12 juni 2017, Contains fulltext : 191513.pdf (publisher's version ) (Closed access)

Published
2017

9. Axonal synapse sorting in medial entorhinal cortex

Author

Schmidt, Helene, Gour, Anjali, Straehle, Jakob, Boergens, Kevin M., Brecht, Michael, Helmstädter, M.N., Schmidt, Helene, Gour, Anjali, Straehle, Jakob, Boergens, Kevin M., Brecht, Michael, and Helmstädter, M.N.

Abstract

20 september 2017, Item does not contain fulltext

Published
2017

10. SynEM, automated synapse detection for connectomics

Author

Staffler, Benedikt, Berning, Manuel, Boergens, Kevin M., Gour, Anjali, Smagt, Patrick van der, Helmstädter, M.N., Staffler, Benedikt, Berning, Manuel, Boergens, Kevin M., Gour, Anjali, Smagt, Patrick van der, and Helmstädter, M.N.

Abstract

Contains fulltext : 276482.pdf (Publisher’s version ) (Open Access)

Published
2017

11. Neuronal and network mechanisms for the emergence of neural computations

Author

Shao, S., Helmstädter, M.N., Gjorgjieva, Julijana, and Radboud University Nijmegen

Subjects
Donders Series, Neurophysiology
Abstract

Contains fulltext : 293084.pdf (Publisher’s version ) (Open Access) The brain is a computational device that detects stimuli from the external world and directs behavioral responses. Accurate computations are, therefore, crucial for the brain. Unlike computers, which use digital signals for their computation, the brain uses analog signals to process information. Also, neurons, the basic I/O units in the brain, are far more complex than the logic gates used in computers. As a result, neural activity involves significant variability. The enriched external world also makes the sensory inputs highly diverse, further increasing neural systems' variability. Starting from this point, we discuss how the nervous system maintains certain invariances under rich variability to achieve stable and accurate computations. We use three specific research projects to illustrate this question from different perspectives. In the first project we propose an efficient neuronal coding theory. We calculate how a group of neurons could adjust their tuning curves to reduce the influence of noise or biophysical constraints and keep the information invariant. In the second project, we investigate the response of the Drosophila peripheral visual system to contrast stimuli. A luminance-sensitive neuron type is indispensable for maintaining invariant contrast perception. Finally, in the third project, we build a neural network model to simulate the generation and evolution of sequential activity in the cerebral cortex under synaptic plasticity. We find that homeostatic plasticity mechanisms that maintain the invariances of overall connectivity and neural activity are necessary to generate sequential activity. These three aspects of research correspond to the three levels of analysis for information processing: computation, algorithm, and implementation, constituting an overall understanding of neural computation. It is important to note that we place an emphasis on understanding neural computation at the neuronal level, which is evident in all of our research projects. Radboud University, 14 juni 2023 Promotores : Helmstädter, M.N., Gjorgjieva, Julijana 307 p.

Published
2023

12. The role of temporal neocortex in threat memory

Author

Dalmay, T., Helmstädter, M.N., Letzkus, M., and Radboud University Nijmegen

Subjects
Neurophysiology
Abstract

Contains fulltext : 226301.pdf (Publisher’s version ) (Open Access) Radboud University, 24 november 2020 Promotor : Helmstädter, M.N. Co-promotor : Letzkus, M. 133 p.

Published
2020

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