Neuronal processing of translational optic flow in the visual system of the shore crabCarcinus maenas

Abstract

SUMMARYThis paper describes a search for neurones sensitive to optic flow in the visual system of the shore crab Carcinus maenas using a procedure developed from that of Krapp and Hengstenberg. This involved determining local motion sensitivity and its directional selectivity at many points within the neurone's receptive field and plotting the results on a map. Our results showed that local preferred directions of motion are independent of velocity, stimulus shape and type of motion (circular or linear). Global response maps thus clearly represent real properties of the neurones' receptive fields. Using this method, we have discovered two families of interneurones sensitive to translational optic flow. The first family has its terminal arborisations in the lobula of the optic lobe, the second family in the medulla. The response maps of the lobula neurones (which appear to be monostratified lobular giant neurones) show a clear focus of expansion centred on or just above the horizon, but at significantly different azimuth angles. Response maps such as these, consisting of patterns of movement vectors radiating from a pole, would be expected of neurones responding to self-motion in a particular direction. They would be stimulated when the crab moves towards the pole of the neurone's receptive field. The response maps of the medulla neurones show a focus of contraction, approximately centred on the horizon, but at significantly different azimuth angles. Such neurones would be stimulated when the crab walked away from the pole of the neurone's receptive field. We hypothesise that both the lobula and the medulla interneurones are representatives of arrays of cells, each of which would be optimally activated by self-motion in a different direction. The lobula neurones would be stimulated by the approaching scene and the medulla neurones by the receding scene. Neurones tuned to translational optic flow provide information on the three-dimensional layout of the environment and are thought to play a role in the judgment of heading.

Vision in the mantispid: a sit‐and‐wait and stalking predatory insect

“…The main function of the lobula is the neural coding of spatial and motion information (via the giant tangential neurones). This is also the case in the lobula of superposition eyes (Horseman et al , 2011). From the lobula, fibres project to the dorsal neuropil of the lateral and medial protocerebrum, from which descending neurones proceed to the neuropils of the neck, leg and flight motor systems.…”

Matched function of the neuropil processing optic flow in flies and crabs: the lobula plate mediates optomotor responses in Neohelice granulata

“…Strausfeld [32] proposed that since the lobula satellite in malacostracans is not LP, optic flow processing should take place in the lobula. While there is a report of neurons possibly involved with translational optic flow in the lobula of crabs [65], no neurons specifically sensitive to rotational optic flow have been found in the lobula so far. Neurons recorded in the lobula of crabs have characteristics compatible with figure detectors, responding more to objects than to panoramic flow-field stimuli.…”

Strange eyes, stranger brains: exceptional diversity of optic lobe organization in midwater crustaceans

“…Based on the finding that other malacostracans and the basal hyperiid Cystisoma are equipped with both lobula and lobula plate, and the second optic chiasma (figure 3), the most parsimonious explanation would be a loss of the lobula in H. galba, a loss of the lobula and the ventral lobula plate in P. sedentaria and a loss of both the lobula and the lobula plate in L. sayana (figures 3 and 4). In addition, given that neurons in the lobula are used for computing object features [17], object motion [18][19][20][21][22] and certain flow field information [23], the complete absence of the lobula in H. galba, P. sedentaria and L. sayana are significant secondary reductions of the optic lobes (figures 3 and 4). Likewise, the loss of ventral or entire lobula plate in P. sedentaria and L. sayana, respectively, are additional significant secondary reductions of the optic lobes (figures 3 and 4).…”

“…The functions of malacostracan optic neuropils have been studied with electrophysiology and optical recording in the brachyuran crabs Neohelice granulata and Carcinus maenas. It was shown that neurons in the lobula are essential for computing object features [17], object motion [18][19][20][21][22] and encoding certain flow field information [23], while those in the lobula plate are implicated in computing wide-field motion and processing optic flow information that mediates optomotor responses [12,13]. Although the experimental evidence came only from a few model species, those functional attributes are generally assumed to apply across malacostracans based on the overwhelming structural conservation and anatomical similarity of those constituent neurons in the optic lobes [12,24].…”