Neural Action Fields for Optic Flow Based Navigation: A Simulation Study of the Fly Lobula Plate Network

Abstract

Optic flow based navigation is a fundamental way of visual course control described in many different species including man. In the fly, an essential part of optic flow analysis is performed in the lobula plate, a retinotopic map of motion in the environment. There, the so-called lobula plate tangential cells possess large receptive fields with different preferred directions in different parts of the visual field. Previous studies demonstrated an extensive connectivity between different tangential cells, providing, in principle, the structural basis for their large and complex receptive fields. We present a network simulation of the tangential cells, comprising most of the neurons studied so far (22 on each hemisphere) with all the known connectivity between them. On their dendrite, model neurons receive input from a retinotopic array of Reichardt-type motion detectors. Model neurons exhibit receptive fields much like their natural counterparts, demonstrating that the connectivity between the lobula plate tangential cells indeed can account for their complex receptive field structure. We describe the tuning of a model neuron to particular types of ego-motion (rotation as well as translation around/along a given body axis) by its ‘action field’. As we show for model neurons of the vertical system (VS-cells), each of them displays a different type of action field, i.e., responds maximally when the fly is rotating around a particular body axis. However, the tuning width of the rotational action fields is relatively broad, comparable to the one with dendritic input only. The additional intra-lobula-plate connectivity mainly reduces their translational action field amplitude, i.e., their sensitivity to translational movements along any body axis of the fly.

Subcellular mapping of dendritic activity in optic flow processing neurons

“…This revised model can account for both the 4.3 VS cell dendritic morphologies are adapted to collect appropriate receptive field components from a spatially organized input repertoire 53 Importantly, the rotational structure of the VS cells' output receptive fields is already present at the dendritic level. This rules out that the axonal inhibitory input from distal onto proximal VS cells is crucial for the upward motion sensitivity in their receptive fields [91].…”

“…A recent simulation study that takes into account a large body of experimental results argued that the columnar feedforward input may encode pure downward motion in a narrow stripe of visual space, whereas horizontal and upward motion components of the receptive fields are imported via lateral inputs [91]. According to this model, proximal VS cells receive horizontal motion input via the dendro--dendritic coupling to dCH, while their frontal upward motion preference is due to the axonal inhibition from a distal VS cell.…”

An Olfactory Circuit Increases the Fidelity of Visual Behavior

“…Similarly, some neck motor neurons generate binocular visual receptive fields by pooling across LPTCs from the two hemispheres (Huston and Krapp, 2008). By contrast to yaw, there is no known singular LPTC that acts as a tuned spatial filter for sideslip optic flow (Borst and Weber, 2011). Nevertheless, investigators report that HS cells, sensitive to horizontal motion, are also sensitive to sideslip (Kern et al, 2005) as well as to vertical motion (Haag and Borst, 2003).…”

Elementary Motion Detection

“…It turns out that network connectivity within the lobula plate plays a critical role (Borst and Weber, 2011). The coupling of neighboring VS-cells through gap junctions leads to a broadening of their receptive fields (Elyada et al, 2009;Farrow et al, 2005).…”

“…In addition to the input from the EMDs, a few connections to other lobula plate tangential cells are known ( fig. 1.9) (Borst and Weber, 2011). The H1 in the left lobula plate excites the HS and CH cell of the right lobula plate Hausen, 1984;Horstmann et al, 2000), which in turn inhibits the right H1 ).…”