Obtaining information from the environment to guide behavior is one of the most fundamental functions of nervous systems. Most animals combine cues from multiple sensory modalities to gain information about their environments. When individual cues are not 100% reliable, combining cues greatly aids decision making and it makes behavior more robust under variable circumstances. My lab studies the neuronal basis for such multisensory integration in the medicinal leech Hirudo verbana. Adult leeches feed on mammalian blood. It lives on the bottom of shallow ponds. When a mammal steps into the water and splashes around, the leech will swim toward the source of the disturbance to find its prey. Leeches can find their prey in total darkness, relying on water-wave sensors on their skin. Remarkably, they can also find their prey using sensory stimuli alone: when placed in a shallow tank, they will swim toward a disturbance in a second tank placed above theirs but mechanically isolated from it. Under more general circumstances, cues from both modalities are available, and leeches must either combine the two modalities, or decide which one is more reliable and selectively ignore the other. The goal of my lab is to find out how their nervous system solves this challenge and produces a coherent decision for subsequent motion
