The Journal of Neuroscience, August 15, 2000, 20(16):6256-6266
Performance of Fly Visual Interneurons during Object Fixation
Bernd
Kimmerle and
Martin
Egelhaaf
Lehrstuhl für Neurobiologie, Fakultät für
Biologie, Universität Bielefeld, D-33501 Bielefeld, Germany
Neurons involved in the processing of optic flow are usually
analyzed using stimuli designed by the experimenter. However, in real
life optic flow depends on locomotive behavior. We characterized the
performance of motion-sensitive neurons in the visual system of the fly
using optic flow as occurring in behavioral situations during object
fixation. Optic flow generated by tethered flying flies in a flight
simulator was subsequently replayed while recording the responses of
two cell types in the fly's motion pathway presumably involved in the
detection of objects and of deviations from a straight flight course,
respectively. FD1b cells, which are representatives of the so-called
figure-detection cells, responded very specifically to object motion.
Although object selectivity of these cells is attributable to
inhibition during large-field motion, the influence of background
motion during object fixation was almost negligible. In contrast, the
cells of the so-called horizontal system (HS cells) are most sensitive
to background motion, as elicited during deviations of the animal from
its course. During object fixation, the responses of HS cells depended
on both object and background motion. The simulated distance of the
background to the fly did not have a strong influence on the responses
of either cell type. The specificity for detecting deviations from a
straight course is enhanced by subtraction of the signals of HS cells
in both halves of the brain. In contrast, the FD1b cells in the two
halves of the brain need to interact in a nonlinear way to ensure
efficient detection of objects.
Key words:
behaviorally relevant stimuli; figure-ground
discrimination; insect; object fixation; optic flow; visual system
Copyright © 2000 Society for Neuroscience 0270-6474/00/20166256-11$05.00/0