Bioinspired figure-ground discrimination via visual motion smoothing
Fig 3
Individual lobula modules extract stimulus features depending on their receptive field structures and direction selectivity.
Data are presented vertically according to their stimulus classes (indicated at the top) and shown based on the input frame at which the foreground figure passed the middle of the visual field. The receptive field of the units in Ir and Il on the EMD array was set as 26° × 26°. (A) Space-time plots of three classes of stimuli with a contrast level of 80% and a moving speed of 66°/sec. Each plot illustrates how the top row (horizontal axis) evolved with time (vertical axis). The top row was randomly selected from the rows of the first frame of stimulus images, so the row evolution characterizes the dynamic evolution of the stimulus. In ‘Bar on Ground’, the background was moving in the direction opposite of the bar (25° × 90°) at the same speed. In ‘Theta Figure’, the elements within the bar (25° × 90°) moved to the left, and the bar itself moved to the right at the same speed. (B) Output of the ON+OFF EMD array (upper row). The area outlined by the white boundary in each panel was magnified and disassembled into rightward (lower-right) and leftward (lower-left) motion components. The element values were enlarged by 10-fold in the lower panels to facilitate an inspection of the difference between the numbers of elements of the two components. (C) Membrane potentials (upper row) and corresponding outputs (lower row) of the units in the Ir, Il, and Im modules. Red boundaries indicate the actual locations of the moving foregrounds at the corresponding instant in time. The membrane potential time courses of the units (marked by white circles) were further examined in (E). (D) Membrane potentials of the units in the Lr, Ll, and Lm modules (simultaneously recorded with those in (C)). (E) Time courses of the membrane potentials of the units marked in (C). The curves are color-coded according to the marking colors of the corresponding units in (C).