Wasp Voodoo Rituals, Venom-Cocktails and the Zombification of Cockroach host

Much like humans, animals may choose to initiate behavior based on
their "internal state" rather than as a response to external stimuli
alone. The neuronal underpinnings responsible for generating this
internal state', however, remain elusive. The parasitoid jewel wasp
hunts cockroaches to serve as a live food supply for its offspring. The
wasp stings the cockroach in the head and delivers a neurotoxic
venom cocktail directly inside the prey's cerebral ganglia to
apparently hijack its free will'. Although not paralyzed, the stung
cockroach becomes a living yet docile zombie' incapable of
self−initiating walking or escape running. We demonstrate that the
venom selectively depresses the cockroach's motivation or drive' to
initiate and maintain walking−related behaviors, rather than inducing
an overall decrease in arousal or a sleep−like' state. Such a decrease
in the drive for walking can be attributed to a decrease in neuronal
activity in a small region of the cockroach cerebral nervous system,
the sub−esophageal ganglion (SEG). Specifically, we have used
behavioral, neuro−pharmacological and electrophysiological methods
to show that artificial focal injection of crude milked venom or
procaine into the SEG of non−stung cockroaches decreases
spontaneous and evoked walking, as seen with naturally−stung
cockroaches. Moreover, spontaneous and evoked neuronal spiking
activity in the SEG, recorded with an extracellular bipolar
microelectrode, is markedly decreased in stung cockroaches as
compared with non−stung controls. By injecting a venom cocktail
directly into the SEG, the parasitoid Jewel Wasp selectively
manipulates the cockroach's motivation to initiate walking without
interfering with other non−related behaviors.