Abstract
ABSTRACTGaining information about the spatial layout of natural scenes is a challenging task that flies need to solve, especially when moving at high velocities. A group of motion sensitive cells in the lobula plate of flies is supposed to represent information about self-motion as well as the environment. Relevant environmental features might be the nearness of structures, influencing retinal velocity during translational self-motion, and the brightness contrast. We recorded the responses of the H1 cell, an individually identifiable lobula plate tangential cell, during stimulation with image sequences, simulating translational motion through natural sceneries with a variety of differing depth structures. A correlation was found between the average nearness of environmental structures within large parts of the cell's receptive field and its response across a variety of scenes, but no correlation was found between the brightness contrast of the stimuli and the cell response. As a consequence of motion adaptation resulting from repeated translation through the environment, the time-dependent response modulations induced by the spatial structure of the environment were increased relatively to the background activity of the cell. These results support the hypothesis that some lobula plate tangential cells do not only serve as sensors of self-motion, but also as a part of a neural system that processes information about the spatial layout of natural scenes.
Highlights
Motion sensitive visual interneurons, like the lobula plate tangential cells (LPTCs) of flies, have been serving as a model system to study how motion information is processed and how orientation behavior is guided (Hausen, 1981; Hausen, 1984; Krapp et al, 2001; Egelhaaf, 2006; Borst et al, 2010; Borst and Euler, 2011; Egelhaaf et al, 2012)
Retinal velocity is just one stimulus parameter that influences the responses of LPTCs: brightness contrast and the specific textural features of environmental structures, such as their spatial frequency content, affect LPTC responses as well
To relate the responses of the H1 cell to these environmental features we quantified these stimulus features (Fig. 3): the average nearness and root-mean-square (RMS) contrast were determined within an analysis window and computed as a function of time (‘timedependent nearness’ and ‘time-dependent contrast’)
Summary
Motion sensitive visual interneurons, like the lobula plate tangential cells (LPTCs) of flies, have been serving as a model system to study how motion information is processed and how orientation behavior is guided (Hausen, 1981; Hausen, 1984; Krapp et al, 2001; Egelhaaf, 2006; Borst et al, 2010; Borst and Euler, 2011; Egelhaaf et al, 2012). Such stimuli are suitable for a systems analysis of motion computation On their basis, the motion signals of LPTCs were shown to depend on stimulus velocity and motion direction, and on the brightness contrast, the spatial frequency and other properties of the stimulus pattern (Dvorak et al, 1980; Hausen, 1981; Egelhaaf and Borst, 1989; Egelhaaf et al, 1989; Hausen and Egelhaaf, 1989). The motion signals of LPTCs were shown to depend on stimulus velocity and motion direction, and on the brightness contrast, the spatial frequency and other properties of the stimulus pattern (Dvorak et al, 1980; Hausen, 1981; Egelhaaf and Borst, 1989; Egelhaaf et al, 1989; Hausen and Egelhaaf, 1989) These experimenter-defined stimuli differ much from what flies see, while behaving in their natural habitats. It is not possible to infer the functional significance of LPTCs solely on this basis
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