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degrees of freedom. A reaction-diffusion system is implemented for gait generation
and altitude control. The gait is induced by a central pattern generator. Waves of
activity propagate in a ring of cells. Individual legs receive movement commands at
different times. Local sensors can change the locomotion pattern, e.g. if a joint sat-
urates. The produced gait is a function of the sensory stimuli from the environment
and the intended movement.
Recently, vertical interactions have been added to the CNN framework. For in-
stance, Roska and Werblin proposed a ten-layered network as a model for retinal
processing [197]. This model has been implemented with a CNN [14].
Model of Contextual Interaction in V1. The retina is only the first computational
module in the human visual system. Lateral interactions are crucial in higher areas
as well, like in the primary visual cortex. Recently, Li [141] proposed a model for
lateral feedback in visual area V1. Its architecture is illustrated in Figure 3.15.
The model consists of a single sheet of columns. Each column represents ori-
ented stimuli by several excitatory neurons that have different preferred orienta-
tions. The excitatory neurons are connected monosynaptically to excitatory neurons
of similar orientation in their neighborhood if they are aligned on a straight line or
an arc segment.
Fig. 3.15. Model of contextual interaction in V1 proposed by Li [141]. Each position is rep-
resented by several orientation-selective cells. Excitatory and inhibitory neurons form pairs
that are reciprocally connected. Local lateral interaction is mediated by monosynaptic exci-
tatory connections and disynaptic connections via inhibitory interneurons according to the
connection pattern shown. Aligned cells of similar orientation excite each other, while non-
aligned cells of similar orientation have inhibitory connections. The model's response to three
different input images is also shown. The model performs texture segmentation, contour en-
hancement and perceptual pop-out (images adapted from [141, 142]).
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