25.1 Sunday, Jan. 4 13:30 Closing the Loop Around Free Behavior During Active Sensing STAMPER, S. A.; VAGVOLGYI, B. P.; FORTUNE, E. S. ; COWAN, N. J.*; Johns Hopkins University; Johns Hopkins University; New Jersey Institute of Technology; Johns Hopkins University email@example.com http://limbs.lcsr.jhu.edu
A central challenge in studying the mechanisms for active sensing is that it necessarily functions as a closed-loop system in which the animal modifies its motor behavior based on sensory feedback to alter ongoing feedback. To address this, we have developed an experimental system that allows us to modify and/or open these feedback loops in a freely behaving animal. We achieve this using refuge tracking behavior in weakly electric knifefish: these fish rapidly swim forward and backward to stay inside a longitudinally moving tube-shaped refuge. While following the refuge, the fish continually perform ancillary movements, the characteristics of which depend on sensory conditions. These "active" movements shape sensory feedback for control (Stamper et al, 2012). Here, we take the next step in analyzing the purpose of these behaviors by actively enhancing or suppressing feedback (aka "reafference") caused by these active movements. In our apparatus, the fish's position is measured at up to 100 frames per second using a custom real-time vision system, allowing us to control the refuge in response to fish movements. Using this system, we can experimentally alter (and even temporarily open) the closed-loop feedback experienced by the animal during refuge tracking, allowing us to examine how changes in sensory feedback caused by active sensing alters ongoing motor programs.