Neural network apparatus

A control method, comprising:

• controlling a parameter of a neural network apparatus, the neural network apparatus including a plurality of neuron circuits, a plurality of synaptic circuits, and a control circuit,
• wherein
• each neuron circuit in the plurality of neuron circuits includes:
• a potential holding circuit configured to receive an output signal output from a synaptic circuit in the plurality of synaptic circuits and hold internal potential changing in accordance with a level or a time width of the received output signal;
• a firing circuit configured to output a firing signal in a case where an absolute value of the internal potential is larger than a firing threshold;
• and
• a firing threshold adjustment circuit configured to increase the firing threshold when the frequency of the firing signal is equal to or higher than a firing upper limit frequency given in advance, and reduce the firing threshold when the frequency of the firing signal is lower than a firing lower limit frequency given in advance, the firing lower limit frequency being equal to or smaller than the firing upper limit frequency, each synaptic circuit in the plurality of synaptic circuits includes:
• a weight storage circuit configured to store a synaptic weight;
• a transmission circuit configured to receive the firing signal output from a pre-synaptic neuron circuit being a neuron circuit in the plurality of neuron circuits and output the output signal to a post-synaptic neuron circuit being a neuron circuit in the plurality of neuron circuits, the output signal being obtained by adding influence of the synaptic weight to the received firing signal;
• and
• a learning circuit configured to, in a case where the firing signal is output from the pre-synaptic neuron circuit, increase the synaptic weight when the absolute value of the internal potential held in the post-synaptic neuron circuit is equal to or larger than a first learning threshold being the learning threshold, and reduce the synaptic weight when the absolute value of the internal potential is smaller than a second learning threshold being the learning threshold, the second learning threshold being equal to or smaller than the first learning threshold, and
• the control method further comprises:
• changing the learning threshold in accordance with frequency of the firing signal output from a target neuron circuit being at least one neuron circuit in the plurality of neuron circuits, the learning threshold being used for changing the synaptic weight stored in one or more synaptic circuits each outputting the output signal to the target neuron in the plurality of neuron circuits.