Multi-joint coordination during walking and foothold searching in the Blaberus cockroach. I. Kinematics and electromyograms

Cockroaches were induced to walk or search for a foothold while they were t ethered above a glass plate made slick with microtome oil. We combined kine matic analysis of leg joint movements with electromyographic (EMG) recordin gs from leg extensor muscles during tethered walking and searching to chara cterize these behaviors. The tethered preparation provides technical advant ages for multi-joint kinematic and neural analysis. However, the behavioral relevance of the tethered preparation is an important issue. To address th is issue, we evaluated the effects of tethering the animals by comparing ki nematic parameters of tethered walking with similar data collected previous ly from cockroaches walking freely on a treadmill at the same speeds. No si gnificant differences between tethered and treadmill walking were found for most joint kinematic parameters. In contrast, comparison of tethered walki ng and searching showed that the two behaviors can be distinguished by anal ysis of kinematics and electrical data. We combined analysis of joint kinem atics and electromyograms to examine the change in multi-joint coordination during walking and searching. During searching, middle leg joints extended during swing rather than stance (i.e., walking) and the coordination of mo vements and extensor motor neuron activity at the coxa-trochanteral and fem ur tibia joints differed significantly during walking and searching. We als o found that the pattern of myographic activity in the middle leg during se arching was similar to that in the front legs during walking.