A system for reinforcement learning, comprising: a plurality of electronic neurons (14,16,18,20); a cross-bar array configured to interconnect the plurality of electronic neurons (14,16,18,20), the cross-bar array comprising: a plurality of axons (14,16)and a plurality of dendrites (18,20) such that the axons (14,16) and dendrites (18,20) are transverse to one another; and multiple electronic synapses, wherein each electronic synapse is at a cross-point junction of the cross-bar array coupled between a dendrite (18,20) and an axon (14,16), each electronic synapse configured for interconnecting a pre-synaptic electronic neuron and a post-synaptic electronic neuron; characterised in that each electronic synapse comprises: three memory elements (31R,31G,31B) configured for maintaining information, wherein one memory element stores a state of the electronic synapse and two memory elements (31G,31B) store update information to be used for updating the state of the electronic synapse; and three axon paths transverse to three dendrite paths forming a 3 x 3 array of 9 junctions, such that the memory elements (31R,31G,31B) reside on the junctions on a diagonal of the array, providing an R bit, a G bit and a B bit; and an update module configured for updating the state of the electronic synapse based on the stored update information in response to a reinforcement signal. a plurality of electronic neurons (14,16,18,20); a cross-bar array configured to interconnect the plurality of electronic neurons (14,16,18,20), the cross-bar array comprising: a plurality of axons (14,16)and a plurality of dendrites (18,20) such that the axons (14,16) and dendrites (18,20) are transverse to one another; and multiple electronic synapses, wherein each electronic synapse is at a cross-point junction of the cross-bar array coupled between a dendrite (18,20) and an axon (14,16), each electronic synapse configured for interconnecting a pre-synaptic electronic neuron and a post-synaptic electronic neuron; characterised in that each electronic synapse comprises: three memory elements (31R,31G,31B) configured for maintaining information, wherein one memory element stores a state of the electronic synapse and two memory elements (31G,31B) store update information to be used for updating the state of the electronic synapse; and three axon paths transverse to three dendrite paths forming a 3 x 3 array of 9 junctions, such that the memory elements (31R,31G,31B) reside on the junctions on a diagonal of the array, providing an R bit, a G bit and a B bit; and an update module configured for updating the state of the electronic synapse based on the stored update information in response to a reinforcement signal. a plurality of axons (14,16)and a plurality of dendrites (18,20) such that the axons (14,16) and dendrites (18,20) are transverse to one another; and multiple electronic synapses, wherein each electronic synapse is at a cross-point junction of the cross-bar array coupled between a dendrite (18,20) and an axon (14,16), each electronic synapse configured for interconnecting a pre-synaptic electronic neuron and a post-synaptic electronic neuron; characterised in that each electronic synapse comprises: three memory elements (31R,31G,31B) configured for maintaining information, wherein one memory element stores a state of the electronic synapse and two memory elements (31G,31B) store update information to be used for updating the state of the electronic synapse; and three axon paths transverse to three dendrite paths forming a 3 x 3 array of 9 junctions, such that the memory elements (31R,31G,31B) reside on the junctions on a diagonal of the array, providing an R bit, a G bit and a B bit; and an update module configured for updating the state of the electronic synapse based on the stored update information in response to a reinforcement signal. three memory elements (31R,31G,31B) configured for maintaining information, wherein one memory element stores a state of the electronic synapse and two memory elements (31G,31B) store update information to be used for updating the state of the electronic synapse; and three axon paths transverse to three dendrite paths forming a 3 x 3 array of 9 junctions, such that the memory elements (31R,31G,31B) reside on the junctions on a diagonal of the array, providing an R bit, a G bit and a B bit; and an update module configured for updating the state of the electronic synapse based on the stored update information in response to a reinforcement signal.