Attentive Decision-Making and Dynamic Resetting of Continual Running SRNNs for End-to-End Streaming Keyword Spotting

Efficient end-to-end processing of continuous and streaming signals is one of the key challenges for Artificial Intelligence (AI) in particular for Edge applications that are energy-constrained. Spiking neural networks are explored to achieve efficient edge AI, employing low-latency, sparse processing, and small network size resulting in low-energy operation. Spiking Recurrent Neural Networks (SRNNs) achieve good performance on sample data at excellent network size and energy. When applied to continual streaming data, like a series of concatenated keyword samples, SRNNs, like traditional RNNs, recognize successive information increasingly poorly as the network dynamics become saturated. SRNNs process concatenated streams of data in three steps: i) Relevant signals have to be localized. ii) Evidence then needs to be integrated to classify the signal, and finally, iii) the neural dynamics must be combined with network state resetting events to remedy network saturation. Here we show how a streaming form of attention can aid SRNNs in localizing events in a continuous stream of signals, where a brain-inspired decision-making circuit then integrates evidence to determine the correct classification. This decision then leads to a delayed network reset, remedying network state saturation. We demonstrate the effectiveness of this approach on streams of concatenated keywords, reporting high accuracy combined with low average network activity as the attention signal effectively gates network activity in the absence of signals. We also show that the dynamic normalization effected by the attention mechanism enables a degree of environmental transfer learning, where the same keywords obtained in different circumstances are still correctly classified. The principles presented here also carry over to similar applications of classical RNNs and thus may be of general interest for continual running applications.