CARTESIAN REPRESENTATION OF STIMULUS DIRECTION - PARALLEL-PROCESSING BY 2 SETS OF GIANT INTERNEURONS IN THE COCKROACH

The cockroach Periplaneta americana responds to wind puffs by turning away, both on the ground and when flying. While on the ground, the ven tral giant interneurons (ventrals) encode the wind direction and speci fy turn direction, whereas while flying the dorsal giant interneurons (dorsals) appear to do so. We report here on responses of these cells to controlled wind stimuli of different directions. Using improved met hods of wind stimulation and of positioning the animal revealed import ant principles of organization not previously observed. All six cells of largest axonal diameter on each side respond preferentially to ipsi lateral winds. One of these cells, previously thought to respond non-d irectionally (giant interneuron 2), was found to have a restricted dir ectional response (Fig. 3). The organization of directional coding amo ng the ventral giant interneurons is nearly identical to that among th e dorsals (Fig. 2). Each group contains, on each side, one cell that r esponds primarily to wind from the ipsilateral front, another primaril y in the ipsilateral rear, and a third responding more broadly to ipsi lateral front and rear. These results are discussed in terms of the me chanisms of directional localization by the assembly of giant interneu rons.