Neuron model. Three stages composed the neuron model used in this paper. The first one is a neuronal adaptation with a gain G
and a time constant T
. In the second stage, this drive is modulated by the OPN activity. In the third stage, the modulated signal is sent to a first order transfer function (gain: α, time constant: T
) representing the membrane potential dynamics with a saturated output between 0 and d
≥0. The crossed circle represents a sum operator. The circled π represents a product.