A major goal in my laboratory has been to unravel the neuronal mechanisms by which an animal hijacks the brain of another animal to manipulate its behavior. A parasitoid wasp slips her stinger through the roach's neck and directly into its brain to inject a cocktail of neurotoxins. The wasp apparently uses sensors along the sides of the stinger to guide it through the brain, a bit like a surgeon snaking his way to an appendix with a laparoscope. She continues to probe the roach's brain until she reaches one particular spot that appears to control the motivation to generate movement. The neuronal underpinnings of motivation, in spite of its major significance in understanding the control of initiation of locomotion, are still poorly understood. During the last few years, insect behaviors that span different behavioral levels of arousal have been studied, from sleep to full arousal. We have found that Dopamine and Dopamine receptors are likely to be involved in the hypokinetic state of stung animals. Interestingly, patients with Parkinson’s disease, in which the Nigro-Striatal DA system has degenerated, show decrease in motivation and deficits in planning, initiation, and execution of movements, one of the hallmarks being the paucity of voluntary movements, or hypokinesia. Hypokinesia is also one of the hallmarks that characterize cockroaches stung by this wasp. Moreover, also freezing during movements, another symptom of Parkinson's, has been observed in stung cockroaches. Our research has been published as several invited reviews and incorporated as a classical case study in numerous Neuroethology and Animal Behavior courses in several universities in the USA and has been become Text Book material. Our work has been presented in the general press (National Geographic, Scientific American and the like and was the object of a special program on the Discovery Channel )
Ectoparasitoid wasps typically use terrestrial arthropods as the food supply for their offspring. Their venoms exert diverse effects on the attacked host, ranging from metabolic and hormonal alterations to specific and fine manipulation of the host behavior. Wasps which manipulate their host's behavior have attracted special interest since in some cases their venom directly affects the host's nervous system. Thus, and especially where the nervous system of the host has been well-studied, the manipulation of host behavior can be correlated with detectable alterations in the host nervous system. This provides a tool not only for the study of parasitoid-host interactions, but also for our understanding of the neural basis of host behavior. The best understood manipulation of host nervous system and behavior is the case of the Sphecid cockroach-hunter, Ampulex compressa. Our main objective is to examine the neuronal circuits targeted by the wasp within the host head ganglia. We will first examine and document the effects of direct venom injections in the head ganglia on cockroach motor behavior, focusing on locomotion. By these means, we will then determine to what extent the circuitry in the head ganglia regulate motor behaviors generated in the thorax. We will focus on walking, flight and escape behaviors, but also righting and swimming. Data will also be collected from cockroaches that have received venom injection into the brain or the SEG or both using a tethered wasp. Once we have established the specific roles in locomotion played by circuits in the head ganglia, we will proceed to identify these circuits and how they are affected by A. compressa venom, using a combination of electrophysiology and imaging. We will also examine the involvement of DA receptors and putative changes in DA receptor density in the venom-induced hypokinesia.