Aspen Center for Physics: Physics of Behavior

Where

Aspen, CO, http://aspenphys.org.

When

May 27 - June 17, 2012

Application Deadline

passed

Registration Deadline

if you were admitted, you must register by March 31, 2012

Register online at

http://aspenphys.org/

Mission Statement

Traditionally the interface between physics and biology has been defined by a simple fact that complex molecules underlie biological phenomena, and such molecules are a natural subject for physical studies. Now we understand that the role of physics in biology is much broader, as physical constraints define the strategies and the biological machinery that living systems use to shape their behavior in the dynamic, noisy, and resource-limited physical world. Neither the physical constraints imposed by the world, nor the tasks that biological systems trying to survive in it perform depend strongly on their structure. Hence studying behavior of living systems has a potential for a unified understanding, which could bring together various subfields of biological physics, from single molecules, to neural computation.

A classic example of such a system is bacterial chemotaxis -- many bacteria will direct its movements towards certain chemicals. The behavioral strategy of bacterium E. coli approaches an optimal solution for navigating up a concentration gradient in light of well-defined physical constraints due to diffusion. This broad view of chemotactic behavior in E. coli has revealed a deeper understanding of some general design principles of biochemical signaling networks, such as how they can produce large output gain over a wide dynamic range, while remaining robust to fluctuations in protein levels and microscopic rates. The study of chemotaxis has clearly demonstrated that the search for physical principles at the systems-level complement reductionist studies at the molecular level, and that some principles emerge only when studying behavior of the network holistically.

Can a similar understanding emerge for other, more complex living systems? For the proposed workshop we will define "behavior" broadly as an input-output relation between a stimulus and an action of the system. To expose participants to a diverse range of systems and to facilitate the development of theories that span living systems, we will invite experts who quantify behavior of a wide range of model organisms. We will address the behavior of molecular circuits through organisms, focusing on exploring motion as possibly optimal adaptive responses given the physical and the statistical structure of environment. Importantly, since constraints on behavior are imposed by the environment, which in turn is influenced by the behavior, we expect to have a presence of ecologists as well.

We expect that the workshop will be structured around the following themes:

Navigation and foraging

Strategies for navigation and search within local environments and across large distances have been studied since the earliest days of ethology. Evidence exist that navigation strategies adapt optimally subject to relevant physiological and environmental constraints. The modern advent of small, lightweight sensors and fast cameras have led to quantitative data movements of individual organisms from single cells to humans. Developing quantitative approaches to the analysis of behaviors that evolve over long time scales poses a particular challenge due to their potentially high-dimensional structure.

Active Sensing

The strategies with which organisms deploy their array of sensors profoundly influence their experience of the natural world. Biological sensors are noisy and number-limited and thus no organism has the capacity to capture sensory signals with arbitrary precision. Under selection pressure to optimally sense available signals, organisms actively collect information from their environment to guide behavioral decisions. Examples include eye movements, echolocation, whisking and locomotion through odor plumes.

Locomotion and rhythmic behavior

For an animal, movement is not translation or rotation of its body relative to an external coordinate system, but rather transformations of shape as measured in its own intrinsic coordinates. The kinematics of the body and the dynamics of neural control both shape cyclic movements that animals make while walking, flying, swimming, chewing, etc. There has been little work relating these movement primitives to larger-scale functional consequences on interactions between the organism and the surrounding world, and the discussion is overdue.

Adaptive responses

All behavior is in response to external stimulation, and the fidelity of the response is limited by the ability of an organism to learn from its environment. Such responses may be deterministic, but often stochastic components of the behavior serve as a bet-hedging strategy against inaccurate learning, cheaters, or inability to respond. Work is needed to achieve a holistic understanding of deterministic and stochastic response strategies in a single context of adaptation to the surrounding world.

Organizers

Ila Fiete, UT Austin

Ilya Nemenman, Emory U

Leslie Osborne, U Chicago

William Ryu, U Toronto

Greg Stephens, Princeton U

Program

Registration for the workshop will be over on March 31. We will build the workshop program soon after, based on the schedule of the registered attendees.