Evaluation of optical motion information by movement detectors

Abstract

The paper is dealing in its first part with a system-theoretical approach for the decomposition of multi-input systems into the sum of simpler systems. By this approach the algorithm for the computations underlying the extraction of motion information from the optical environment by biological movement detectors is analysed. In the second part it concentrates on a specific model for motion computation known to be realized by the visual system of insects and of man. These motion detectors provide the visual system with information on both, velocity and structural properties of a moving pattern. The last part of the paper deals with the functional properties of two-dimensional arrays of movement detectors. They are analyzed and their relations to meaningful physiological responses are discussed.

Visual afferences to flight steering muscles controlling optomotor responses of the fly

“…6. The retinal motion patterns are initially evaluated by a two-dimensional retinotopic array of local movement detectors (Reichardt 1987;Egelhaaf et al 1988). This local motion information segregates at the level of the third visual ganglion into two pathways that are specifically tuned to large-field and small-field motion and, therefore, have been referred to as large-field and small-field system, respectively (Egelhaaf 1987).…”

Properties of individual movement detectors as derived from behavioural experiments on the visual system of the fly

“…As has been shown before, the visual system of the house-fly is a convenient model system for studying various visual information processing tasks and, in particular, the principle mechanisms underlying the evaluation of motion from the visual surround (e.g. Reichardt 1986Reichardt , 1987. In the present study it has been concluded that the instantaneous response of a single movement detector -even to a stimulus pattern moving with a constant velocity in only one direction -does not directly signal the correct motion.…”

“…Instead, it is modulated by the spatial phase of the stimulus pattern and may even signal motion in the wrong direction. It is particularly obvious from a recent theoretical formulation of the movement detector response (Reichardt and Guo 1986;Egelhaaf and Reichardt 1987;Reichardt 1987), which has been used here for the model predictions, that spatial integration over sufficiently large areas of the visual field is a simple means for these temporal modulations of the response to disappear. This prediction turned out to be correct for the motion detection system of the fly as is found in the behavioural measurements of the present study as well as in electrophysiological experiments on large-field motion sensitive neurones in the third visual ganglion (Egelhaaf, unpublished results).…”

“…which has been derived previously (Reichardt and Guo 1986) and further elaborated in subsequent studies (Egelhaaf and Reichardt 1987;Reichardt 1987). ds(t)/dt represents the instantaneous pattern velocity, where s(t) is the time-dependent spatial displacement of the pattern.…”

Responses of blowfly motion-sensitive neurons to reconstructed optic flow along outdoor flight paths

“…The 2DMD is formed by 460·170 equally spaced pairs of elementary motion detectors (EMDs), oriented orthogonally with horizontal or vertical preferred directions, respectively; one pair centred on each image pixel location. The EMDs are simple correlationtype motion detectors (reviews: Borst and Egelhaaf 1989;Reichardt 1987) composed of a first-order linear low-pass filter and an arithmetic multiplication of the low-pass filtered signal originating from one photoreceptor and the unfiltered signal originating from a neighbouring photoreceptor. The spatial sampling distance was set to 4°and the time constant of the temporal low-pass filter was 4 ms.…”