CENTRAL GENERATION OF GROOMING MOTOR PATTERNS AND INTERLIMB COORDINATION IN LOCUSTS

Coordinated bursts of leg motoneuron activity were evoked in locusts w ith deefferented legs by tactile stimulation of sites that evoke groom ing behavior. This suggests that insect thoracic ganglia contain centr al pattern generators for directed leg movements. Motoneuron recording s were made from metathoracic and mesothoracic nerves, after eliminati ng all leg motor innervation, as well as all input from the brain, sub esophageal ganglion, and prothoracic ganglion. Strong, brief trochante ral levator motoneuron bursts occurred, together with silence of the s low and fast trochanteral depressor motoneurons and activation of the common inhibitor motoneuron. The metathoracic slow tibial extensor mot oneuron was active in a pattern distinct from its activity during walk ing or during rhythms evoked by the muscarinic agonist pilocarpine. Pr eparations in which the metathoracic ganglion was isolated from all ot her ganglia could still produce fictive motor patterns in response to tactile stimulation of metathoracic locations. Bursts of trochanteral levator and depressor motoneurons were clearly coordinated between the left and right metathoracic hemiganglia and also between the mesothor acic and the ipsilateral metathoracic ganglia. These data provide clea r evidence for centrally generated interlimb coordination in an insect .