Abstract
Neurons in the visual system of the blowfly have large receptive fields that are selective for specific optic flow fields. Here, we studied the neural mechanisms underlying flow–field selectivity in proximal Vertical System (VS)-cells, a particular subset of tangential cells in the fly. These cells have local preferred directions that are distributed such as to match the flow field occurring during a rotation of the fly. However, the neural circuitry leading to this selectivity is not fully understood. Through dual intracellular recordings from proximal VS cells and other tangential cells, we characterized the specific wiring between VS cells themselves and between proximal VS cells and horizontal sensitive tangential cells. We discovered a spiking neuron (Vi) involved in this circuitry that has not been described before. This neuron turned out to be connected to proximal VS cells via gap junctions and, in addition, it was found to be inhibitory onto VS1.
Highlights
In blowflies, the processing of large field motion is performed in the posterior division of the third neuropile of the optic lobe, the lobula plate
All Vertical System (VS) cells are electrically coupled in a chain-like manner via axo-axonal gap junctions
Proximal VS cells are electrically coupled to dCH which in turn is coupled to HSN
Summary
The processing of large field motion is performed in the posterior division of the third neuropile of the optic lobe, the lobula plate. Cells are found responding preferentially to vertical motion like the 10 Vertical System cells (VS, VS1–VS10) as well as cells which are best activated by horizontal motion like the three Horizontal System (HS)- and the two Centrifugal Horizontal (CH) cells While these tangential cells respond to motion stimuli in a graded potential manner, tangential cells can be found that produce full blown action potentials (Haag and Borst, 1996; Hengstenberg, 1977). This is particular the case for proximal VS cells which have local preferred directions that are distributed to match the flow field occurring during a rotation of the fly (Krapp and Hengstenberg, 1996) These cells respond best to upward motion in the frontal part, horizontal progressive motion in the dorsal part and to downward motion in the lateral part of their visual field
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