Abstract-This paper summarises recent efforts into implementing a model of the inner hair cell and auditory nerve on a neuromorphic hardware platform, the SpiNNaker machine. Such an implementation exploits the massive parallelism of the target architecture to obtain real-time modelling to a biologically realistic number of human auditory nerve fibres. The potential for incorporating this implementation into a full-scale digital realtime model of the human auditory pathway is then discussed. The mammalian ear extracts many useful features from a sound stimulus that have been essential in evolutionary survival. Such attempts to replicate these capabilities using various methods of frequency analysis and computer algorithms currently cannot match human performance in a range of hearing tasks . It is believed that the brain's unique stimulus encoding of spiking neuron action potentials, and the non-linear adaptive response of the inner ear, are contributing factors to what enables us to perform fast and efficient sound processing [4] . To achieve a realistic model of the mammalian 'auditory pathway' is the aim of this (and further) research. Using such a model we hope to gain a better understanding of the mechanisms in our auditory brain that explain human level hearing performance. The auditory pathway begins with a sound pressure wave travelling into the outer ear and eventually displacing the Tympanic Membrane (TM) which separates the outer and middle ear. Inside the middle ear the TM connects to the cochlea via three ossicle bones to continue (and amplify) this displacement into the inner ear cochlea. The cochlea is a coiled, liquid filled organ that converts the TM displacement into a series of travelling waves along its distance, from base to apex. The frequency components of the sound stimulus dictate the location along the cochlea that will experience the most displacement along its Basilar Membrane (BM). High frequencies are absorbed at the basal regions and progressively lower frequencies are absorbed towards the apex of the cochlea. The cochlea is lined with many motion sensitive cells that detect the localised displacements of the BM, known as Inner Hair Cells (IHCs). Fig. 1 shows the structure of an IHC and the afferent Auditory Nerve (AN) fibres that innervate each IHC. The stereocilia 'hairs' at the top of the cell move according with the motion of the section of the BM the cell is closest to. When the stereocilia move in the axis of sensitivity they allow an influx of calcium ions (Ca 2+ ) to enter the cell body. This influx of Ca 2+ increases the likelihood of neurotransmitter release from the containing vesicles at the 'active regions' around the bottom of the IHC where AN fibres innervate the cell membrane. A release of vesicle neurotransmitter causes an action potential (spike) to occur in the corresponding AN fibre. Fig. 2 shows a diagram of an uncoiled cochlea; it illustrates how specific characteristics of a sound stimulus are represented by spiking activity in AN fibres. Fig. 1 . A simplified inner hair cell with afferent auditory nerve fibres innervating the base of the cell. It performs mechanotransduction in the inner ear, converting physical hair displacement to auditory nerve action potentials.
James et al REF uses SpiNNaker machine to implement a model of the auditory nerve and ear's inner hair cell, which is shown to be comparable with a MATLAB version of the same model algorithms but have better scalability.
Parallel distribution of an inner hair cell and auditory nerve model for real-time application
2017 IEEE Biomedical Circuits and Systems Conference (BioCAS)
2017 IEEE Biomedical Circuits and Systems Conference (BioCAS)
Medicine Computer Science