High-conductance states on a neuromorphic hardware system

Under typical synaptical stimulation, cortical neurons exhibit a total membrane conductance which, compared to a situation without any input spikes, is significantly increased. This results in a shorter membrane time constant and thus in an increased capability of the neuron to detect coincidences in its synaptic input. For this study, a neuromorphic hardware device was utilized, which does not provide direct access to its membrane conductances. Motivated by the aim of finding biologically realistic configuration regimes for the chip operation, a purely spike-based method for the estimation of membrane conductances is presented, allowing to test the hardware membrane dynamics. A proof of principle is given by pure software simulations. Hardware results are presented which illustrate the functionality of the method and show the possibility to generate high-conductance states in the utilized VLSI neurons. In the final section, limits and useful implications of the proposed method are discussed.