Meeting Abstract
Limb size has a large effect on determining where it rests. A large limb’s resting position is predominantly determined by gravitational forces. As a limb becomes smaller, it is progressively dominated by passive forces. All control systems have to deal with these material properties, but there are few measurements of these material properties in an intact animal. We take advantage of genetic tools in flies to measure how the passive properties of the limb and active control from motor neurons (MNs) work to determine the resting leg position. In this study, we measure the angle of the coxa and femur-tibia joints at rest during both active (MNs are active), and passive (MNs are genetically silenced by expressing the green-light inhibiting chanelrhodopsin, GtACR1 in motor neurons using VGlut promoter) stop positions. After reconstructing the passive and active leg stops in a 3D space we see two distinct clusters for the two types of stops. Using the passive limb configuration, we were able to measure the passive properties of each joint in the leg. The stop positions for passive and active stops were distinct, and indicate that the active stops are being controlled by MNs. To test this hypothesis, and to characterize whether the distinct stop position during active stops represent baseline MN activity, or whether there are dedicated MNs that control the joint position at rest, we will perform calcium imaging in the same experimental setup. Together, we will provide a quantitative description of the role that neural activity and passive forces play in the control of a fly’s active resting leg position.
