Possible configurations of active units (activation function h(Δ,θ)) in the absence of global recurrent feedback connections. The active areas are shaded. (A) If initially all neurons are OFF and the external current was increased from zero, only the units, which are unconditionally ON (group I) are active. (B) If initially all units are ON and the external current sweeps the parameters space downward, there is a deactivation wave propagating with the boundary between regions II and III (red slanted arrow). The active region extends indefinitely in the direction of a large Δ and is truncated in this and following figures. (C) A more complex pattern of activation in the history dependent region (III) can be produced by a complex pattern of inputs. For the profile shown, current was going up, down, up, and down.