Department of Neurobiology, Stanford University, Stanford, United States
Limor Freifeld
Department of Electrical Engineering, Stanford University, Stanford, United States; Research Laboratory of Electronics, MIT Electrical Engineering and Computer Science Department, Cambridge, United States
Mark Horowitz
Department of Electrical Engineering, Stanford University, Stanford, United States
Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, United States; Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, United States; Department of Physics, University of Illinois at Urbana-Champaign, Urbana, United States
The function of the brain is unlikely to be understood without an accurate description of its output, yet the nature of movement elements and their organization remains an open problem. Here, movement elements are identified from dynamics of walking in flies, using unbiased criteria. On one time scale, dynamics of walking are consistent over hundreds of milliseconds, allowing elementary features to be defined. Over longer periods, walking is well described by a stochastic process composed of these elementary features, and a generative model of this process reproduces individual behavior sequences accurately over seconds or longer. Within elementary features, velocities diverge, suggesting that dynamical stability of movement elements is a weak behavioral constraint. Rather, long-term instability can be limited by the finite memory between these elementary features. This structure suggests how complex dynamics may arise in biological systems from elements whose combination need not be tuned for dynamic stability.
