Optic flow representation in the optic lobes of Diptera: modeling the roleof T5 directional tuning properties

An evolutionarily conserved system of small retinotopic neurons in dipteran insects, called bushy T-cells, provides information about directional moti on to large collator neurons in the lobula plate. Physiological and anatomi cal features of these cells provide the basis for a model that is used to i nvestigate requirements for generating optic flow selectivity in collators while allowing for evolutionary variations. This account focuses on the rol e of physiological tuning proper-ties of T5 neurons. Various flow fields ar e defined as inputs to retinotopic arrays of T5 cells, the responses of whi ch are mapped onto collators using innervation matrices that promote select ivity for flow type and position. Properties known or inferred from physiol ogical and anatomical studies of neurons contributing to motion detection a re incorporated into the model: broad tuning to local motion direction and the representation of each visual sampling unit by a quartet of small-field T5-like neurons with orthogonal preferred directions. The model predicts h itherto untested response properties of optic flow selective collators, and predicts that selectivity for a given flow field can be highly sensitive t o perturbations ill physiological properties of the motion detectors.