The invention is a 
system (1) that simulates a 
decision process in a 
mammalian brain with respect to a motion characteristic relating to a visually observed 
body posture of a body by means of a simulated visual path comprising an interface towards a simulated neuronal structure, the 
system includes an interface that converts at least 
luminescence information of the observed body into an 
optical flow data stream that delivers information relating to the visually observed body and that can be processed in the simulated 
neuron structure, the 
system being a feed-forward system that can be coupled to the simulated 
neuron structure. And from the 
visual observation that the decision comprises hierarchically: the simulated visual path and its interface (3, 3L, 3R); a simulated local 
motion direction detection 
neuron structure (4, 4L, 4R) for detecting the 
motion direction by means of a 
receptive field; a simulated opposition 
motion detection neuron structure (5, 5L, 5R) for detecting opposition motion at least relating to expansion and contraction; a simulated complex 
pattern detection neuron structure (6, 6L, 6R) for globally detecting an 
optical flow pattern over the entire 
visual observation and according to the evolution of the entire 
visual observation during the time, the detectable pattern being a prototype pattern; and a simulated motion 
pattern detection neuron structure (7, 7LR) for detecting a motion pattern and providing a decision regarding a motion characteristic. According to the invention, the neurons of the simulated motion 
pattern detection neuron structure (7, 7LR) comprise a forgetting ability that is a function of the 
delay and for each neuron an activity of the neuron.