Many animals use motion vision information to control dynamic behaviors. Predatory
animals, for example, show an exquisite ability to detect rapidly moving prey followed
by pursuit and capture. Such target detection is not only used by predators but can
also play an important role in conspecific interactions. Male hoverflies (Eristalis tenax),
for example, vigorously defend their territories against conspecific intruders. Visual
target detection is believed to be subserved by specialized target tuned neurons that
are found in a range of species, including vertebrates and arthropods. However, how
these target-tuned neurons respond to actual pursuit trajectories is currently not well
understood. To redress this, we recorded extracellularly from target selective
descending neurons (TSDNs) in male Eristalis tenax hoverflies. We show that they
have dorso-frontal receptive fields, with a preferred direction up and away from the
visual midline, which cluster into TSDNLeft and TSDNRight. We reconstructed visual
flow-fields as experienced during pursuits of artificial targets (black beads). We
recorded TSDN responses to six reconstructed pursuits and found that each neuron
responded consistently at remarkably specific time points, but that these time points
differed between neurons. We found that the observed spike probability was correlated
with the spike probability predicted from each neuron’s receptive field and size tuning.
Interestingly, however, the overall response rate was low, with individual neurons
responding to only a small part of each reconstructed pursuit. In contrast, the
TSDNLeft and TSDNRight populations responded to substantially larger proportions of
the pursuits, but with lower probability. This large variation between neurons could be
useful if different neurons control different parts of the behavioral output.</p