SPONBERG, S.*; SPENCE, A.; FULL, R.J.; Univ. of CA, Berkeley; Univ. of CA, Berkeley; Univ. of CA, Berkeley: Testing Neural Control Models for Antenna-based Tactile Navigation in Cockroaches

Navigation requires neural sensing of environmental features. Cockroaches use antennal tactile contact to track walls during running in low light environments. A kinematic response to wall turning occurs in as little as 40 ms (Camhi & Johnson, 1999). Neural signals encoding the change in wall orientation are mediated by mechanoreceptors located on the antenna flagellum. Simple biomechanical control models have shown that the cockroach�s dynamic response to tracking a step change in wall angle is unstable if proportional information (distance from wall) alone is used (Cowan and Full, 2005). The model predicts that the rate of change of distance from wall (derivative information) is required from sensors. The simplest source of derivative control predicts a phasic response in antennal mechanoreceptors during an increase in bending – equivalent to a change in wall orientation. We recorded extracellularly from the antennal nerve of restrained Death�s head cockroaches (Blaberus discoidalis) using sharpened tungsten electrodes. The antenna was flexed both with a point deflection and using a mechanically actuated wall segment to simulate turns during running. We calculated the rms value of the net antenna nerve response to describe the power in the neural signal. Neural activity significantly increased during and immediately after the stimulus (Paired t-test, p-value < 0.001). The post-stimulus signal power subsequently decreased from peak power indicating a phasic response. Our results confirm a phasic response in antennal mechanoreceptors demonstrating that derivate control information as predicted from the control model is available for use in cockroach navigation. Support by an NSF FIBR grant to R.J. Full and the Fannie and John Hertz Foundation.