Avoidance of collisions is critical to survival and the activity of sensory and motor neurons thought to be involved in visually-guided escape has been studied in several species. However, the mechanisms by which visual information processed in sensory areas leads to the preparation and execution of escape remains poorly understood. The current project addresses this question by studying escape of freely behaving locusts in response to simulated objects approaching on a collision course and by coupling these studies with electrophysiological recordings of neuronal activity both in restrained and freely moving animals. The locust will be studied because the neural pathways involved in generating escape behavior are well characterized and are accessible for neurophysiological investigation. The project will use a multi-disciplinary approach, combining behavior, neurophysiology and computer engineering to relate the generation of escape behaviors to the coding of visual stimuli in the activity of individual nerve cells. Gabbiani and his collaborators will first characterize how the timing of various stages of escape jumps elicited in locusts by the approach of an object on a collision course depends on the speed and size of the approaching object. Animals will be filmed with a high speed-video system as they jump from the simulated approach of objects, or looming stimuli. Next, in restrained animals, the electrical activity of neurons sensitive to looming, which relay information from sensory to motor centers in the locust central nervous system, will be examined in response to similar stimulus conditions. One individual neuron thought to be critical in this process, the descending contralateral motion detector (DCMD) neuron, will be studied in detail. In parallel to these neurophysiological studies, computer engineers on the project will develop a miniature digital wireless recording and transmission system able to be carried by the locust. This system will transmit up to eight channels of neuronal data from electrodes implanted in the insect's nervous system, including signals from the DCMD cell studied in the restrained locust. The small device will affixed to the back of locusts to monitor nervous activity in real time during escape jumps. In separate experiments, the muscular activity leading to the generation of jumps will be monitored as well. Taken together, this study will for the first time investigate quantitatively the relation between stimulus parameters, the activity of sensory neurons and the motor stages of a visually guided escape behavior in freely behaving animals, thus leading to an integrated understanding of the connection between its sensory and motor components. This project also has a broader imact beyond the research community. Dr. Gabbiani has worked, and will continue to work, closely with a high school science teacher in his laboratory to develop high school science curriculum modules on the neural control of behavior and the integration of computer engineering with biology. The project will also support the interdisciplinary training of several graduate students.
