לוח שנה משולב

What are the neural processes that lead to a decision to approach another individual in need and help them out of a tight spot? Multiple factors weigh in on this decision, including empathic arousal and social identity. The drive to act prosocially in response to others distress is evolutionarily rooted in mechanisms underlying parental behavior and group living. In humans, helping involves socio-emotional and cognitive components, and recruits brain regions involved in affective empathy arousal, executive function and motivation. This talk will present an overview of the rat Helping Behavior Test, which investigates the complex response leading to rescue of trapped conspecifics, and examine evidence to ask whether similar capacities are involved in rat helping. We’ll explore the idea that rat helping is motivated by empathy, what is the difference between social and prosocial reward, and whether helping is motivated by valuation of others’ outcomes. I will share what we’ve learned about the distinct neural network that is associated with empathy and prosocial behavior, and discuss findings of ingroup bias, adolescent helping, and interactions with rat immune function and wellbeing. We’ll ask what is the link between prosocial motivation and aggression, and what is the role of the social group in these behaviors.

Trail interactions occur when past particle trajectories bias future motion, rendering the system out of thermodynamic equilibrium. While such systems are abundant in nature, their understanding is limited to the single-particle level or phenomenological mean-field theories. Here, we introduce a minimal model of many trail-interacting particles that extends this paradigm to the fluctuating collective level. Particles diffuse while depositing long-lasting repelling/attracting trails that act as a shared memory field, coupling their dynamics across time and space. Using stochastic density functional theory, we derive fluctuating hydrodynamic equations and analyze analytically and numerically the resulting behaviors. We show that memory, coupled with fluctuations, fundamentally reshapes collective dynamics; In the repulsive case, the particle density displays superdiffusive spreading characterized by transient clustering and ballistic motion; In the attractive case, the system condensates in finite time into frozen, localized states. Our results establish general principles for trail-interacting systems and reveal how persistent fields generate novel instabilities and self-organization. FOR THE LATEST UPDATES AND CONTENT ON SOFT MATTER AND BIOLOGICAL PHYSICS AT THE WEIZMANN, VISIT OUR WEBSITE: https://www.bio

Over the last five years my lab has explored the hypothesis that people suffering from major depressive disorder show pathological decision-making. In a series of experiments we demonstrate that the psychological “reference point” against which all hedonic experience is benchmarked is represented in the Anterior Cingulate Cortex of the Monkey. In parallel work, Helen Mayberg’s group has shown that the severity of a patient’s depression can be decoded from activity in this same area. We used this information and foraging theory to develop a behavioral tool for measuring the reference point in humans and found that a 3 minute version of our task can be used to diagnose depression with the same accuracy as a 60m clinical interview. The implications of this finding for our understanding of the mechanism of depression will be discussed.

Text-based 2D image editing models have recently reached an impressive level of maturity, motivating a growing body of work that uses them to drive 3D edits. While effective for appearance-based modifications, such 2D-centric 3D editing pipelines often struggle with fine-grained 3D editing, where localized structural changes must be applied while strictly preserving an object’s overall identity.

To address this limitation, we propose Prox-E, a training-free framework that enables fine-grained 3D control through an explicit, primitive-based geometric abstraction. Our framework first abstracts an input 3D shape into a compact set of geometric primitives. A pretrained vision-language model then edits this abstraction to specify primitive-level changes, which are subsequently used to guide a 3D generative model. This enables fine-grained, localized modifications while preserving unchanged regions of the original shape.

Through extensive experiments, we show that Prox-E consistently balances identity preservation, shape quality, and instruction fidelity more effectively than existing approaches, including 2D-based 3D editors and training-based methods.

Bio:

Etai Sella is a fourth-year PhD student at Tel Aviv University, supervised by Hadar Averbuch-Elor and Or Patashnik. His research focuses on making generative AI more controllable and editable, with an emphasis on 3D editing. He is currently an intern at Snap Research.

The input to the Multiway Cut problem is a weighted undirected graph, with nonnegative edge weights, and $k$ designated terminals. The goal is to partition the vertices of the graph into~$k$ parts, each containing exactly one of the terminals, such that the sum of weights of the edges connecting vertices in different parts of the partition is minimized. The problem is APX-hard for $k\ge3$. The currently best-known approximation algorithm for the problem for arbitrary~$k$, obtained by Sharma and Vondr\'ak [STOC 2014] more than a decade ago, has an approximation ratio of 1.2965. We present an algorithm with an improved approximation ratio of 1.2787. Also, for small values of $k \ge 4$ we obtain the first improvements in 25 years over the currently best approximation ratios obtained by Karger, Klein, Stein, Thorup, and Young [STOC 1999]. (For $k=3$ an optimal approximation algorithm is known.)

Our main technical contributions are new insights on rounding the LP relaxation of C{\u{a}}linescu, Karloff, and Rabani [STOC 1998], whose integrality ratio matches Multiway Cut's approximability ratio, assuming the Unique Games Conjecture [Manokaran, Naor, Raghavendra, and Schwartz, STOC 2008]. First, we introduce a generalized form of a rounding scheme suggested by Kleinberg and Tardos [FOCS 1999] and use it to replace the Exponential Clocks rounding scheme used by Buchbinder, Naor, and Schwartz [STOC 2013] and by Sharma and Vondr\'ak. Second, while previous algorithms use a mixture of two, three, or four basic rounding schemes, each from a different family of rounding schemes, our algorithm uses a computationally-discovered mixture of hundreds of basic rounding schemes, each parametrized by a random variable with a distinct probability distribution, including in particular many different rounding schemes from the same family. We give a completely rigorous analysis of our improved algorithms using a combination of analytical techniques and interval arithmetic.

Joint work with Joshua Brakensiek, Neng Huang and Aaron Potechin.