Integrated Calendar

https://drive.google.com/file/d/1KqUjdjfrPYXDCNa3_0Z83i-vBxl-dgrL/view?usp=sharing

Formation and retrieval of distinct memories are complementary processes that put conflicting requirements on neuronal computations in the hippocampus, especially when memories closely resemble each other. How this challenge is resolved in hippocampal circuits to guide memory-based decisions is unclear. To address this question, our group uses in vivo 2-photon calcium imaging and whole-cell recordings from hippocampal subregions in head-fixed mice trained to distinguish between novel and familiar virtual-reality environments. We find that granule cells consistently show a small transient depolarization of their membrane potential upon transition to a novel environment. This synaptic novelty signal is sensitive to local application of atropine, indicating that it depends on metabotropic acetylcholine receptors. A computational model suggests that the observed transient synaptic response to novel environments leads to a bias in the granule cell population activity, which can in turn drive the downstream attractor networks to a new state, thereby favoring the switch from generalization to discrimination when faced with novelty. Such a novelty-driven cholinergic switch may enable flexible encoding of new memories while preserving stable retrieval of familiar ones.


zoom link to join-https://weizmann.zoom.us/j/96608033618?pwd=SEdJUkR2ZzRBZ3laUUdGbWR1VFJTdz09

Meeting ID: 966 0803 3618
Password: 564068
Host: Dr. Rita Schmidt rita.schmidt@weizmann.ac.il tel: 9070

Zoom LInk:
https://weizmann.zoom.us/j/95962123886?pwd=ZWV6WkwxKzlNU00zRU1ER3JIWkg4Zz09


In this talk I will describe cutting-edge bio and nanotechnologies for engineering functional tissues and organs, focusing on the design of new biomaterials mimicking the natural microenvironment, or releasing biofactors to promote stem cell recruitment and tissue protection. In addition, I will discuss the development of patient-specific materials and 3D-printing of personalized vascularized tissues and organs. Finally, I will show a new direction in tissue engineering, where, micro and nanoelectronics are integrated within engineered tissues to form cyborg tissues and bionic organs.

A subset of megathrust earthquakes produce anomalously large tsunamis for their magnitude. All of these recorded ‘tsunami earthquakes’ in the past 50 years had extensional aftershocks in the upper plate. These include the two largest and most destructive earthquakes of that period, the 2004 Sumatra–Andaman and the 2011 Tohoku events. Evidence from the region of Tohoku indicates that normal fault slip in the upper plate during the earthquake may have contributed to the tsunami size. Here we present a numerical model that shows how a reduction of the dip of a subducting slab, on a timescale of millions of years, can result in an extensional fault failure above a megathrust earthquake on timescales of seconds to months. Slab dip reduction bends the upper plate so that the shallow part fails in extension when a megathrust rupture relieves compressional stress. This results in a distribution of extensional aftershocks comparable to that seen above the Tohoku megathrust. Volcanic arc migra- tion and uplift data for Tohoku and several other tsunami earthquakes is consistent with slab dip reduction. The collection of more such data might identify other areas of tsunami hazard related to slab dip reduction.

The question of how to measure a smell has troubled scientists for over a century. It was none other than Alexander Graham Bell that raised the challenge: "we have very many different kinds of smells, all the way from the odor of violets and roses up to asafoetida. But until you can measure their likenesses and differences you can have no science of odor”. Such a measure of smell can be naturally derived from a model of olfactory perceptual quality space, and several such models have recently been put forth. These typically rely on finding mathematical rules that link odorant structure to aspects of odor perception.
Here, I collected 49,788 perceptual odor estimates from 199 participants, and built such a model, finalizing a physicochemical measure of smell. This measure, expressed in radians, predicts real-world odorant pairwise perceptual similarity from odorant structure alone. Using this measure, I met Bell's challenge by accurately predicting the perceptual similarity of rose, violet and asafoetida, from their physicochemical structure. Next, based on thousands of comparisons, I identified a cutoff in this measure, below 0.05 radians, where discrimination between pairs of mixtures becomes highly challenging. To assess the usefulness of this measure, I investigated whether it can be used to create olfactory metamers, namely non-overlapping molecular compositions that share a common percept. Characterizing the link between physical structure and ensuing perception in vision and audition, and the creation of perceptual entities such as metamers, was important towards understanding their underlying dimensionality, brain mechanisms, and towards their ultimate digitization. I suggest that olfactory metamers can similarly aid these goals in olfaction.

Zoom link to join: https://weizmann.zoom.us/j/93360836031?pwd=dDZEdTQ1QUkxUVVONVErVm9CcUJWQT09



Meeting ID: 933 6083 6031
Password: 591230

Hydrological systems are inherently non-linear and exhibit an enormous structural and functional heterogeneity. Strikingly, we can nevertheless successfully simulate stream flow generation and the water balance of river catchments with rather simple models that are largely incompatible with the frequently reported subscale process heterogeneity and non-linearity. Here we argue that subscale structural heterogeneity and randomness must not prevent the emergence of functional simplicity. On the contrary, we found simplicity to emerge at rather small scales, reflecting self-organization in hydrological functioning not despite but due to subscale small-scale heterogeneity and the dissipative nature of hydrological process. While we acknowledge that hydrological landscapes are heterogeneous, they are by no means a random product. Catchments exhibit a considerable spatial organisation, which manifests through structured patterns of topography, soil, vegetation, self-similar surface and subsurface drainage networks and most prominently through ubiquitous preferential flow phenomena. While this organized “catchment from” does strongly determine present storage, cycling and release of water, energy and chemical species, this catchment form has in turn been shaped by of water, energy, and nutrients of the past. Is this “co-evolution” just chance or manifested self-organization? This question has been inspiring many scientists to search for thermodynamic principles that link form and function in the Earth system. Here we will present evidence that a thermodynamic and information theoretic perspective opens up new avenues for (i) diagnosing and explaining self-organization in hydrological dynamics, (i) upscaling of constituting relations and (i) using thermodynamic optimality for hydrological predictions.