On the identification of movement detectors in the fly optic lobe

Abstract

Intracellular recordings were made in the lobula-lobula plate ganglia of the optic lobes of the blowfliesCalliphora erythrocephala, Phaenicia sericata, and the flesh-flySarcophaga (species unknown) with the following results: 1. This region of the optic lobe is electrically very active. A large variety of response types were encountered. We concentrated upon recording from directionally selective movement detectors (DSMD's). 2. We were able to record from all eight classes of DSMD's reported previously from extracellular recordings. We found that it was possible to impale selectively a vertical or a horizontal DSHD, even though these neurons cannot be seen in the live preparation. Recordings were stable for as long as 40 min in cells that subsequent intracellular staining showed to be 2–10 μm in diameter. 3. Iontophoretic injection of the fluorescent dye procion yellow M4RS works very well in this system. We have achieved 100% recovery of injected cells, with partial fills being a rarity. 4. To date all DSMD's were elements of the lobula plate. 5. DSMD's with preferred directions in the horizontal plane lie in the anterior portion of the lobula plate and project to the ventral periesophageal region. The anatomical “horizontal system” described by Pierantoni (1973) and Strausfeld (1975) are horizontal DSMD's. Smaller cells, mimetic to the “horizontal system” are also horizontal DSMD's. Wide-field cells (Strausfeld, 1970, 1975) may be horizontal DSMD's. 6. DSMD's with preferred directions in the vertical plane lie in the posterior region of the lobula plate and project to the dorsal periesophageal region. These cells are a system of small diameter (2–4 μm) elements that are in close association with a system of larger cells (“vertical system”) described by Pierantoni (1973) and Strausfeld (1975). 7. Intracellular recordings established directly that some horizontal and vertical DSMD's have binocular visual fields.