Diffusion Models
diffusion models
Prof Mark Humphries
The Humphries’ lab at the University of Nottingham is seeking a postdoc to study the neural basis of foraging, in collaboration with the groups of Matthew Apps (Birmingham) and Nathan Lepora (Bristol). Whether choosing to leave one shop for another, switching TV programs, or seeking berries to eat, humans and other animals make innumerable stay-or-leave decisions, but how we make them is not well understood. The goal of this project is to develop new computational accounts of stay-or-leave decisions, and use them to test hypotheses for how humans, primates, and rodents learn and make these decisions. The work will draw on and develop new reinforcement learning and accumulation (e.g. diffusion) models of decision-making. The Humphries’ group researches fundamental insights into how the joint activity of neurons encodes actions in the world (https://www.humphries-lab.org). This post will join our developing research program into how humans and other animals learn to make the right decisions (e.g. https://doi.org/10.1101/2022.08.30.505807).
Ann Kennedy
The Kennedy lab is recruiting for multiple funded postdoctoral positions in theoretical and computational neuroscience, following our recent lab move to Scripps Research in San Diego, CA! Ongoing projects in the lab span topics in: reservoir computing with heterogeneous cell types, reinforcement learning/control theory analysis of complex behavior, neuromechanical whole-organism modeling, diffusion models for imitation learning/forecasting of mouse social interactions, joint analysis/modeling of effects of internal states on neural + vocalization + behavior data. With additional NIH and foundation funding for: characterizing progression of behavioral phenotypes in Parkinson’s, modeling cellular/circuit mechanisms underlying internal state-dependent changes in neural population dynamics, characterizing neural correlates of social relationships across species. Projects are flexible and can be tailored to applicants’ research and training goals, and there are abundant opportunities for new collaboration with local experimental groups. San Diego has a fantastic research community and very high quality of life. Our campus is located at the Pacific coast, at the northern edge of UCSD and not far from the Salk Institute. Postdoctoral stipends are well above NIH guidelines and include a relocation bonus, with research professorship positions available for qualified applicants.
Jagath Rajapakse
Two post-doctoral research positions are available in AI-inspired drug design in the Biomedical Computing Group headed by Professor Jagath Rajapakse at Nanyang Technological University, Singapore, for a period of three years starting from 1 July 2025. The project investigates the design of biologics (peptides and antibodies) as anticancer therapeutic agents by using eXplainable AI (XAI) and generative AI (genAI). First, we build predictive AI models such as large language models (LLM) for predicting binding affinities of biologics. Second, we use XAI approaches such as integrated gradients for identifying the features of predictive models and the mechanism of action of biologics. Third, using these features as constraints, we will use genAI techniques such as LLM and diffusion models to generate biologics with anti-cancer properties. The candidate will develop necessary predictive AI, XAI and genAI methods for design of anti-cancer biologics.
Generative models for video games (rescheduled)
Developing agents capable of modeling complex environments and human behaviors within them is a key goal of artificial intelligence research. Progress towards this goal has exciting potential for applications in video games, from new tools that empower game developers to realize new creative visions, to enabling new kinds of immersive player experiences. This talk focuses on recent advances of my team at Microsoft Research towards scalable machine learning architectures that effectively capture human gameplay data. In the first part of my talk, I will focus on diffusion models as generative models of human behavior. Previously shown to have impressive image generation capabilities, I present insights that unlock applications to imitation learning for sequential decision making. In the second part of my talk, I discuss a recent project taking ideas from language modeling to build a generative sequence model of an Xbox game.
Generative models for video games
Developing agents capable of modeling complex environments and human behaviors within them is a key goal of artificial intelligence research. Progress towards this goal has exciting potential for applications in video games, from new tools that empower game developers to realize new creative visions, to enabling new kinds of immersive player experiences. This talk focuses on recent advances of my team at Microsoft Research towards scalable machine learning architectures that effectively capture human gameplay data. In the first part of my talk, I will focus on diffusion models as generative models of human behavior. Previously shown to have impressive image generation capabilities, I present insights that unlock applications to imitation learning for sequential decision making. In the second part of my talk, I discuss a recent project taking ideas from language modeling to build a generative sequence model of an Xbox game.
Unique features of oxygen delivery to the mammalian retina
Like all neural tissue, the retina has a high metabolic demand, and requires a constant supply of oxygen. Second and third order neurons are supplied by the retinal circulation, whose characteristics are similar to brain circulation. However, the photoreceptor region, which occupies half of the retinal thickness, is avascular, and relies on diffusion of oxygen from the choroidal circulation, whose properties are very different, as well as the retinal circulation. By fitting diffusion models to oxygen measurements made with oxygen microelectrodes, it is possible to understand the relative roles of the two circulations under normal conditions of light and darkness, and what happens if the retina is detached or the retinal circulation is occluded. Most of this work has been done in vivo in rat, cat, and monkey, but recent work in the isolated mouse retina will also be discussed.
NMC4 Short Talk: Transient neuronal suppression for exploitation of new sensory evidence
Decision-making in noisy environments with constant sensory evidence involves integrating sequentially-sampled evidence, a strategy formalized by diffusion models which is supported by decades behavioral and neural findings. By contrast, it is unknown whether this strategy is also used during decision-making when the underlying sensory evidence is expected to change. Here, we trained monkeys to identify the dominant color of a dynamically refreshed checkerboard pattern that doesn't become informative until after a variable delay. Animals' behavioral responses were briefly suppressed after an abrupt change in evidence, and many neurons in the frontal eye field displayed a corresponding dip in activity at this time, similar to the dip frequently observed after stimulus onset. Generalized drift-diffusion models revealed that behavior and neural activity were consistent with a brief suppression of motor output without a change in evidence accumulation itself, in contrast to the popular belief that evidence accumulation is paused or reset. These results suggest that a brief interruption in motor preparation is an important strategy for dealing with changing evidence during perceptual decision making.
Bayesian distributional regression models for cognitive science
The assumed data generating models (response distributions) of experimental or observational data in cognitive science have become increasingly complex over the past decades. This trend follows a revolution in model estimation methods and a drastic increase in computing power available to researchers. Today, higher-level cognitive functions can well be captured by and understood through computational cognitive models, a common example being drift diffusion models for decision processes. Such models are often expressed as the combination of two modeling layers. The first layer is the response distribution with corresponding distributional parameters tailored to the cognitive process under investigation. The second layer are latent models of the distributional parameters that capture how those parameters vary as a function of design, stimulus, or person characteristics, often in an additive manner. Such cognitive models can thus be understood as special cases of distributional regression models where multiple distributional parameters, rather than just a single centrality parameter, are predicted by additive models. Because of their complexity, distributional models are quite complicated to estimate, but recent advances in Bayesian estimation methods and corresponding software make them increasingly more feasible. In this talk, I will speak about the specification, estimation, and post-processing of Bayesian distributional regression models and how they can help to better understand cognitive processes.
How to simulate and analyze drift-diffusion models of timing and decision making
My talk will discuss the use of some of these four, simple Matlab functions to simulate models of timing, and to fit models to empirical data. Feel free to examine the code and the relatively brief book chapter that explains the code before the talk if you would like to learn more about computational/mathematical modeling.
Modeling neural switching via drift-diffusion models
COSYNE 2025