Neuro-Inspired Speech Recognition Based on Reservoir Computing

This chapter investigates the potential of recurrent spiking neurons for classification problems. It presents a hybrid approach based on the paradigm of Reservoir Computing. The practical applications based on recurrent spiking neurons are limited due to the lack of learning algorithms. Most of the previous work in the literature has focused on feed forward networks because computation in these networks is comparatively easy to analyse. The details of such networks have been reported in detail in (Haykin, 1999) (Pavlidis et al., 2005) (Bohte et al., 2000). Recently, a strategy proposed by Maass (Maass et al., 2002) and Jaeger (Jaeger, 2001) offers to overcome the burden of recurrent neural networks training. In this paradigm, instead of training the whole recurrent network only the output layer (known as readout neuron) is trained. This chapter investigates the potential of recurrent spiking neurons as the basic building blocks for the liquid or so called reservoir. These recurrent neural networks are termed as microcircuits which are viewed as basic computational units in cortical computation (Maass et al., 2002). These microcircuits are connected as columns which are linked with other neighboring columns in cortical areas. These columns read out information from each other and serve both as reservoir and readout. The reservoir is modeled as a dynamical system perturbed by the input stream where only readouts are trained to extract information from the reservoir. The basic motivation behind investigating recurrent neurons is their potential to memorise relevant events over short periods of time (Maass et al., 2002). The use of feedback enables recurrent networks to acquire state representation which makes them suitable for temporal based applications such as speech recognition. It is challenging to solve such problems with recurrent networks due to the burden of training. The paradigm of reservoir computing also referred to as liquid computing relaxes the burden of training because only an output layer is trained instead of training the whole network. The work presented in this chapter analyses the theoretical framework of Reservoir Computing and demonstrates results in terms of classification accuracy through the application of speech recognition. The design space for this paradigm is split into three domains; front end, reservoir, and back end. This work contributes to the identification of suitable front and back end processing techniques along with stable reservoir dynamics, which provides a reliable framework for classification related problems. The work presented in this chapter suggests a simple and efficient biologically plausible approach based on a hybrid implementation of recurrent spiking neurons and classical feed