Fig. 6

Response to periodic stimuli A range of responses to periodic stimuli are depicted. (a-d): Responses of models to a periodic signal with a fixed amplitude and varying mean value. The typical response is one where upon increasing basal(mean) value the amplitude of oscillations of the response decreases. In (a), DR08.M1 shows a maintenance of the mean of the output (explained analytically). In (b, c) KR09 and KR11 behave typically and the mean is not maintained. The effect of saturation is seen in the difference between (b) and (c). In (d), CO09.M2 behaves atypically, i.e. the amplitude of oscillations and their mean value reach a maximum and then decrease. (e-h): Responses of the models to a periodic signal with a fixed basal level and varying amplitude. The typical response is one where increasing the amplitude of the input increases the amplitude of the output. In (e-g) we see this typical behaviour but with maintenance of output mean value for DR08.M1 (e), while this is not the case for the other models (KR09, KR11). The saturation effect in (g) exhibits itself as a pronounced asymmetry of oscillations (relative to (f)). In (h), CO09.M2 behaves atypically: oscillations and their mean value reach a maximum and then decrease (the lowest and highest basal levels correspond to zero oscillations in (d) and (h))