Synaptic circuit and neural network apparatus

A neural network apparatus comprising:

• neuron circuits each functioning as a neuron in a neural network;
• and
• synaptic circuits each functioning as a synapse in the neural network, wherein each of the synaptic circuits includes
• a weight storage circuit configured to store a synaptic weight indicating a first value or a second value;
• and
• a transmission circuit configured to
• receive a firing signal output from a pre-synaptic neuron circuit, and
• supply an output signal to a post-synaptic neuron circuit, the output signal being obtained by adding, to the firing signal, influence of the synaptic weight stored by the weight storage circuit, wherein
• the post-synaptic neuron circuit holds an internal potential varying in response to reception of the output signal, and
• the weight storage circuit is configured to, when the firing signal is received from the pre-synaptic neuron circuit,
• perform comparison to determine whether or not the internal potential held by the post-synaptic neuron circuit is equal to or higher than a set potential, and
• cause the synaptic weight to change to indicate the first value or the second value with a first probability set in advance in accordance with a comparison result as to whether or not the internal potential is equal to or higher than the set potential, and
• the weight storage circuit is configured to cause the synaptic weight to change to indicate the first value with a preset second probability regardless of whether or not the firing signal is received from the pre-synaptic neuron circuit.