On the correlation model: Performance of a movement detecting neural element in the fly visual system

Abstract

The applicability of the basic principles of the correlation model to the description of the activity of a movement detecting neuron in the third optic ganglion of the fly's visual system has been investigated. This wide field neuron is supposed to sum the outputs of a large number of correlators (i.e. multiplying units followed by time averagers) that are distributed over almost the entire eye. The model describes and predicts the experimental results in a satisfactory way if a uniformly distributed system or correlators is assumed. The sampling base of the correlators in this system equals the interommatidial angles deltaphi. The half width of the spatial sensitivity distribution of the visual inputs of the correlators, deltarho, is equal to the half width of the retinula cells of the 1--6 system.

Encoding of Visual Motion Information and Reliability in Spiking and Graded Potential Neurons

“…The high coherence value found in motion-sensitive neurons studied here is at first glance amazing, because directionally selective motion detection is known to be an inherently nonlinear process (Reichardt, 1961(Reichardt, , 1987Poggio and Reichardt, 1973;Zaagman et al, 1978;Egelhaaf, 1989, 1993). In general, the signals delivered by a motion detector are unlike a speedometer and do not exhibit a linear dependence on stimulus velocity.…”

Adaptive strategies in fly vision: On their image-processing qualities

“…If we subtract Y x (t) 9 we are left with Y 2 (t) which-in reaction to a step function-mimics a pure differentiating filter performance, especially for small values of τ 2 . Be cause of the fact that Y x (t) is the response of a real pole filter with time constant τ 2 (in CSMP: Y x (t) = REALPL(T 2 , x(t))) a good approximation of a differenti ating filter as it will be used by us as a component in the modeling of the adaptive phenomena to be presented is Fig.…”

Motion computation and visual orientation in flies

“…The performance of the local movement detectors in the fly's visuaf system can be approximated surprisingly well by this formal scheme under both steadystate and transient conditions (Giitz, 1972;Zaagman et al, 1978;Mastebroek et al, 1980;Buchner, 1984;Reichardt, 1987;Egelhaaf and Reichardt, 1987;Borst and Egelhaaf, 1989,199O;Borst, 1989, 1992;Egelhaaf et al, 1989a). Of course, the brain performs these computations by synaptic interactions between different nerve cells.…”