Neuronal representation of optic ̄ow experienced by unilaterally blinded ̄ies on their mean walking trajectories

Asymmetries in the optic ̄ow on both eyes may indicate an unintended turn of an animal and evoke compensatory optomotor responses. On a straight path in an evenly structured environment, the optic ̄ow on both eyes is balanced corresponding to a state of optomotor equilibrium. When one eye is occluded an optomotor equilibrium is expected to be reached on a curved path provided that the translatory optic ̄ow component is cancelled by a superimposed rotation. This hypothesis is tested by analysing how the HSE cell, a constituent element of the ̄y's optomotor system, represents optic ̄ow in behavioural situations. The optic ̄ow as seen on the average trajectory of freely walking monocular ̄ies is reconstructed. This optic ̄ow is used as stimulus of the HSE cell in electrophysiological experiments and as input of a model of the ̄y's optomotor system. The responses of the HSE cell and of the model ̄uctuate around the resting potential. On average, they are much smaller than the responses evoked by optic ̄ow experienced on a straight path. These results corroborate the hypothesis that the mean trajectory of monocular ̄ies corresponds to a path of optomotor