Insect Optic Glomeruli: Exploration of a Universal Circuit for Sensorimotor Processing

Electrophysiological investigations of dragonfly target-selective descending neurons yielded the following findings: (1) Outdoor experiments with 2 families of dragonflies with different prey capture strategies revealed family-specific differences in the receptive fields. (2) Real objects moving in 3 dimensions elicited greater responses to nearby small objects than predicted from responses to images on a flat visual display. (3) Outdoor experiments and experiments with expanding images on a flat display revealed looming-object preference of 2 TSDNs, which appear to predict time-to-contact. (4) TSDNs showed extremely high spike rates with the raised body temperatures (30-35 deg C) seen in naturally behaving dragonflies. (5) Two TSDNs were tuned to looming objects, coding for time-to-contact. (6) Two TSDNs were identified whose spikes carry predictive information about future object position. Investigation of flight behavior revealed that take-off direction is a linear function of the prey's angular velocity 28 ms before takeoff. Collaboration with Dr. Anthony Leonardo (HHMI-JFRC) led to development of a flight arena, a chronic electrode implantation technique, and a miniature telemetry chip, paving the way for wireless recording of TSDN activity during prey interception. The original document contains color images.