לוח שנה משולב

The world around us is barely stable. To maintain constancy of perception, neuronal circuits adopt multiple mechanisms, each carefully tailored to grant the system with computational fidelity in the face of variable stimuli, yet to enable flexibility of computation in certain contexts. During my PhD I investigated the mechanisms that underlie retinal direction-selectivity. Using electrophysiology and modelling approaches, I will show how several mechanisms cooperate to maintain stability in the circuit’s response to moving objects carrying distinct characteristics. This stability is compromised when the retina is confronted by a repetitive light-adapting stimulus that changes the receptive field of cells in several layers of the circuit. Intriguingly, these changes in the cells’ receptive field expose antagonistic center-surround organization of direction coding: the center receptive field supports response to one direction, while the surround supports response to the opposite direction. Center-surround antagonism is thought to enhance spatial discrimination, but this is the first evidence for its contribution to retinal direction selectivity. This provides an example of how the retina elegantly implements computational motifs that are reminiscent of those found in higher brain regions, using just a handful of cell types, already at the first station of the visual system.

(If you are not from the neuroscience field, please check out THIS).

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Meeting ID: 910 5845 2206
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Weather and climate extremes such as cold spells, heat waves, heavy precipitation or windstorms have long been considered challenging to adequately predict a few days in advance. Even at shorter time scales, it is sometimes difficult to estimate the magnitude and impact area accurately. Therefore, they have been selected as one of the grand challenges by the World Climate Research Program. Several studies suggest that extreme temperatures or heavy precipitation events may become more frequent and more intense with climate change, making this topic even more pertinent.
The ability to predict the development of any dynamical system (a system that evolves in time), depends on: 1) its persistence, meaning that a persistent system will be easier to predict and 2) the number of options the system can develop into/from, meaning that systems with a small number of options will be easier to predict. Recent advances in dynamical systems theory allow to efficiently compute these metrics from model data. Our earlier findings show that the dynamical systems metrics can serve as an extremely informative qualitative method for evaluating the predictability and dynamics of synoptic systems over the Eastern Mediterranean.
The talk will discuss this novel dynamic approach and its recent applications in extreme weather forecasting, as well as in climate model projections over the Eastern Mediterranean.

During early life the neural code must develop to appropriately transform sensory inputs into behavioural outputs. However little is known about how developments in neural representations directly impact on behaviour. By combining behavioural analysis with 2-photon calcium imaging at multiple timepoints from 4 to 15 dpf in the optic tectum of developing zebrafish larvae, we demonstrate a link between the maturity of neural coding in the visual brain and developmental changes in visually-guided behavior. We show that visually-driven hunting behavior improves from 4 to 15 days post-fertilization, becoming faster and more accurate. During the same period population activity in parts of the optic tectum refines, improving decoding and information transmission for particular spatial positions. Together these results show that developmental signatures of an emerging neural code can be directly related to observable properties of behaviour.

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Meeting ID: 966 0803 3618
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Host: Dr. Rita Schmidt

rita.schmidt@weizmann.ac.il tel: 9070

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Meeting ID 7576151783
Password – 050925

Although animals are known to heavily rely on chemical signals for intraspecies communication, the matter of human chemical communication remains greatly contentious. I will present evidence supporting the claim that humans, just like other animals, rely on bodily-odors to effectively navigate the social world. First, I will present a quantification of people’s overt olfactory-sampling behavior. Of approximately 400 respondents, 94% acknowledged engaging in smelling their close relationships, and approximately 60% acknowledged sniffing strangers. Next, we tested if this olfactory information is employed for socially-relevant behavioral decisions, such as trust, a key element in human socialization. We found that subliminal exposure to body-odor increased implicit trustworthiness attributed to anthropomorphic non-humans. Finally, I will describe the effect of a specific body-volatile, Hexadecanal (HEX), on human impulsive aggression. Using validated behavioral paradigms, we observed a remarkable dissociation: sniffing HEX blocked aggression in men, but triggered aggression in women. Using functional brain imaging, we uncovered a pattern of brain activity mirroring behavior: In both men and women, HEX increased activity in an area implicated in the perception of social cues. Hex then modulated functional connectivity in a brain network implicated in aggressive behavior in a sex-dependent manner.
Altogether, the thesis puts forward the hypothesis that chemosignals are a form of human social communication. Under this premise, human sampling behavior of self and others’ body-volatiles provides one with important information that, in turn, affects behaviors central to human society, such as trust and aggression.

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Meeting ID: 980 3151 7872
Password: 976632

The Hadley circulation is a key element of the climate system. It is traditionally defined as the zonally averaged meridional circulation in the tropics, therefore treated as a zonally symmetric phenomenon. However, differences in temperature between land and sea cause zonal asymmetries on Earth, dramatically affecting the circulation. This longitudinal dependence of the meridional circulation evokes questions about where and when the actual large scale tropical circulation occurs. Here, we look into the connection between the longitudinally dependent meridional circulation, and the actual large scale transport of air in the tropics using a coupled Eulerian and Lagrangian approach. Decomposing the velocity field into rotational and divergent components, we identify how each component affects the actual circulation. We propose an alternative definition for the circulation, that describes the actual path of air parcels in the tropics, as a tropical atmospheric conveyor belt. We further investigate this definition, analyzing the circulation under climate change and its effect on precipitation changes. We show that in order to predict future climate, the regionality and three-dimensionality of the large-scale tropical circulation must be taken into account. We find that the changes in the circulation vary significantly over longitude, and are overlooked when analyzing the zonally averaged meridional circulation. The circulation is strengthening and expanding in the center of the Pacific, a region where the circulation barely existed in past. On the other hand, the circulation is weakening in the Indo-Pacific region, where it was the most significant in the past. These differences appear as a shift in the region of ascent of the conveyor belt, that is revealed when analyzing the decomposed vertical wind. The pattern of weakening of the ascent in the Indo-Pacific and strengthening in the center of the Pacific explains the projected changes in precipitation. The Indo-Pacific region is drying, while the precipitation in the center of the Pacific is intensifying.