Neural Mechanisms of Visual Course Control in Insects

Neural encoding of behaviourally relevant visual-motion information in the fly

“…In systems such as the retina of the horseshoe crab [5,6], it is now feasible to analyse the neuronal representation of visual input as it is experienced during behaviour (reviewed in Refs [7,8]). Until now, however, in most systems the underlying neuronal mechanisms have been difficult to unravel.In the fly it is possible to employ both quantitative behavioural approaches as well as in vivo electrophysiological and imaging methods to analyse how behaviourally relevant visual input is processed [9][10][11][12][13][14][15][16][17][18][19][20]. Although the latter techniques are mainly employed in the blowfly, which is relatively big, they are complemented by studies of the smaller fruitfly, Drosophila, where a broad range of genetic approaches can be applied to dissect the visual system in an increasingly specific way [21,22].…”

“…Optic flow is an important source of information about self-motion and the three-dimensional layout of the environment, not only for flies but for most moving animals including humans (Box 1, [4,[23][24][25]). Flies exploit optic flow to guide their locomotion [13] and to control compensatory head movements [26], and understanding the computational principles underlying optic-flow processing in flies could provide insights into visual-motion analysis in general.Information processing in visual systems is constrained by the spatial and temporal characteristics of the sensory input and by the biophysical properties of the neuronal circuits. Hence, to understand how visual systems encode behaviourally relevant information, we need to know about both the computational capabilities of the nervous system and the natural conditions under which animals normally operate.…”

“…Optic flow is an important source of information about self-motion and the three-dimensional layout of the environment, not only for flies but for most moving animals including humans (Box 1, [4, [23][24][25]). Flies exploit optic flow to guide their locomotion [13] and to control compensatory head movements [26], and understanding the computational principles underlying optic-flow processing in flies could provide insights into visual-motion analysis in general.…”

Photo-ablation of single neurons in the fly visual system reveals neural circuit for the detection of small moving objects

“…Visual stimulus conditions were slightly modified as compared with that specified in the legend of In a total of 9 experiments one of three identified interneurons (equatorial horizontal (HSE) cell, dorsal centrifugal horizontal (DCH) cell, ventral centrifugal hori-zontal (VCH) cell) in the blowfly's third visual ganglion was individually filled with 6-carboxy-fluorescein. All these cells respond best to rotatory binocular large-field motion [18] and, thus, could play a role in the circuit tuning the FDl-cell to small-field and relative motion.…”

“…The posterior part of the third visual ganglion is the main center of motion computation in the blowfly's brain. There, about 50 directionally selective interneurons with large receptive fields can be identified individually by their anatomical structure and functional properties [18]. All of these so-called tangential cells acquire their motion sensitivity by spatially integrating with their extended dendritic trees over retinotopically organized local motion detectors (for review see ref.…”