To navigate in the world, an animal's brain must produce commands to move, change direction, and negotiate obstacles. In the insect brain, the central complex integrates multiple forms of sensory information and guides locomotion during behaviors such as foraging, climbing over barriers, and navigating to memorized locations. These roles suggest that the central complex influences motor commands, directing the appropriate movement within the current context. Such commands are ultimately carried out by the limbs and must therefore interact with pattern generators and reflex circuits that coordinate them. Recent studies have described how neurons of the central complex encode sensory information: neurons subdivide the space around the animal, encoding the direction or orientation of stimuli used in navigation. Does a similar central-complex code directing movement exist, and if so, how does it effect changes in the control of limbs? Recording from central-complex neurons in freely walking cockroaches (Blaberus discoidalis), we identified classes of movement-predictive cells selective for slow or fast forward walking, left or right turns, or combinations of forward and turning speeds. Stimulation through recording wires produced consistent trajectories of forward walking or turning in these animals, and those that elicited turns also altered an inter-joint reflex to a pattern resembling spontaneous turning. When an animal transitioned to climbing over an obstacle, the encoding of movement in this new context changed for a subset of cells. These results indicate that encoding of movement in the central complex participates in motor control by a distributed, flexible code targeting limb reflex circuits.

An advantage of legged locomotion is the ability to climb over obstacles. We studied deathhead cockroaches as they climbed over plastic blocks in order to characterize the leg movements associated with climbing. Movements were recorded as animals surmounted 5.5-mm or 11-mm obstacles. The smaller obstacles were scaled with little change in running movements. The higher obstacles required altered gaits, leg positions and body posture. The most frequent sequence used was to first tilt the front of the body upward in a rearing stage, and then elevate the center of mass to the level of the top of the block. A horizontal running posture was re-assumed in a leveling-off stage. The action of the middle legs was redirected by rotations of the leg at the thoracal-coxal and the trochanteral-femoral joints. The subsequent extension movements of the coxal-trochanteral and femoral-tibial joints were within the range seen during horizontal running. The structure of proximal leg joints allows for flexibility in leg use by generating subtle, but effective changes in the direction of leg movement. This architecture, along with the resulting re-direction of movements, provides a range of strategies for both animals and walking machines.Keywords Climbing AE Center of mass AE Body-substrate angle AE Kinematics AE Joint angle Abbreviations CoM center of mass AE CTr coxatrochanter joint AE FTi femur-tibia joint AE T 1 first thoracic (prothoracic) segment or leg AE T 2 second thoracic (mesothoracic) segment or leg AE T 3 third thoracic (metathoracic) segment or leg AE ThC thorax-coxa joint AE TrF trochanter-femur joint

SUMMARYWithin natural environments, animals must be able to respond to a wide range of obstacles in their path. Such responses require sensory information to facilitate appropriate and effective motor behaviors. The objective of this study was to characterize sensors involved in the complex control of obstacle negotiation behaviors in the cockroach Blaberus discoidalis. Previous studies suggest that antennae are involved in obstacle detection and negotiation behaviors. During climbing attempts, cockroaches swing their front leg that then either successfully reaches the top of the block or misses. The success of these climbing attempts was dependent on their distance from the obstacle. Cockroaches with shortened antennae were closer to the obstacle prior to climbing than controls, suggesting that distance was related to antennal length. Removing the antennal flagellum resulted in delays in obstacle detection and changes in climbing strategy from targeted limb movements to less directed attempts. A more complex scenario -a shelf that the cockroach could either climb over or tunnel under -allowed us to further examine the role of sensory involvement in path selection. Ultimately, antennae contacting the top of the shelf led to climbing whereas contact on the underside led to tunneling However, in the light, cockroaches were biased toward tunnelling; a bias which was absent in the dark. Selective covering of visual structures suggested that this context was determined by the ocelli. Supplementary material available online at

A biofuel cell incorporating a bienzymatic trehalase|glucose oxidase trehalose anode and a bilirubin oxidase dioxygen cathode using Os complexes grafted to a polymeric backbone as electron relays was designed and constructed. The specific power densities of the biofuel cell implanted in a female Blaberus discoidalis through incisions into its abdomen yielded maximum values of ca. 55 μW/cm(2) at 0.2 V that decreased by only ca. 5% after ca. 2.5 h of operation.

Animals negotiating complex natural terrain must consider cues around them and alter movement parameters accordingly. In the arthropod brain, the central complex (CC) receives bilateral sensory relays and sits immediately upstream of premotor areas, suggesting that it may be involved in the context-dependent control of behavior. In previous studies, CC neurons in various insects responded to visual, chemical, and mechanical stimuli, and genetic or physical lesions affected locomotor behaviors. Additionally, electrical stimulation of the CC led to malformed chirping movements by crickets, and pharmacological stimulation evoked stridulation in grasshoppers, but no more precise relationship has been documented between neural activity in the CC and movements in a behaving animal. We performed tetrode recordings from the CC of cockroaches walking in place on a slippery surface. Neural activity in the CC was strongly correlated with, and in some cases predictive of, stepping frequency. Electrical stimulation of these areas also evoked or modified walking. Many of the same neural units responded to tactile antennal stimulation while the animal was standing still but became unresponsive during walking. Therefore, these CC units are unlikely to be reporting only sensory signals, but their activity may be directing changes in locomotion based on sensory inputs.