Possible functions of a population of descending neurons in the honeybee's visuo-motor pathwayN.J. Bidwell and L.J. Goodman
School of Biological Sciences, Queen Mary and Westfield College, Mile End Rd, London E1 4ND, UK
Abstract - An identified population of honeybee descending neurons (DNs) responds to wide-field motion over the compound eyes. They give non-habituating, directionally selective responses which adapt to continued motion. Contrast sensitivity functions show the responses depend on luminance, contrast, spatial and temporal frequency. The distribution of the DNs' outputs in the thoracic ganglia is consistent with changes in muscular activity required for particular compensatory movements. These features suggest the DNs lie along the optomotor pathway. The DNs' responses have different time-courses. This might reflect distinctions in their putative inputs and between pathways implicated in different aspects of visually mediated flight control. The responses of horizontal DNs to contraction and expansion and to unidirectional motion were compared revealing differences in the way they integrate the monocular components of binocular flow-fields and how velocity and spatial structure effects this integration. It is possible the DNs are convergence site(s) for substrates underlying different behaviours each triggered by specific optical flow templates.
Key words: descending neuron / vision / motion sensitivity / directional selectivity