Understanding auditory nerves for better implants
The 'Neurophysiological correlates of the anatomically discrete organization of the auditory nerve' (NCAN) project aimed to find relative physiological correlates by recording from big samples of auditory nerve (AN) fibres in single animals. These were focused at a specific cochlear region and their responses were examined. A new correlation analysis was developed so researchers could quantify temporally locked responses to random stimuli. The analysis improves the chances of observing a discrete organisation and was thus widely used in the AN and cochlear nucleus. The approach also allows for the study of temporal relationships between neurons. The correlograms produced from this analysis, used to visualise data in correlation matrices, produced from this analysis reflect differences between two fibres in each of the three domains researchers expected to find them: – the magnitude spectrum, the phase spectrum and the overall delay. Early analyses of temporal patterns of neural responses to broadband noise suggested that the extent of correlation jumps indicating discrete organisation is smaller or comparable to random temporal jittering in the AN's neural responses. Thus, NCAN project partners discovered that they could not demonstrate quantal organisation in the auditory nerve using current methods. The results of this project have the potential to further understanding of the electric-neural interface between cochlear implants and the auditory nerve, and promise benefits promise major benefits for better sound- coding strategies in cochlear implants.
