Forward- and backpropagation in a silicon dendrite

We have developed an analog very-large-scale integrated (aVLSI) electronic circuit that emulates a compartmental model of a neuronal dendrite, The hor izontal conductances of the compartmental model are implemented as a switch ed capacitor network. The transmembrane conductances are implemented as tra nsconductance amplifiers. The electrotonic properties of our silicon cable are qualitatively similar to those of the ideal passive cable that is commo nly used to model mathematically the electrotonic behavior of neurons. In p articular the propagation of excitatory postsynaptic potentials is realisti c, and we are easily able to emulate such classical synaptic integration mo dels as direction selectivity: We are also able to emulate the backpropagat ion into the dendrite of single somatic spikes and bursts of spikes. Thus, this silicon dendrite is suitable for incorporation in detailed silicon neu rons operating in real-time; in particular for the emulation of forward- an d backpropagating electrical activities found in real neurons.